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Growth and composition of eucalyptus and maize on Kenya soils fertilized with phosphate and indole acetic acid

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Growth and composition of eucalyptus and maize on Kenya soils fertilized with phosphate and indole acetic acid
Creator:
Keter, Joseph Kipkorir A
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English
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xvi, 205 leaves : ; 28 cm.

Subjects

Subjects / Keywords:
Corn ( jstor )
Crops ( jstor )
Fertilizers ( jstor )
Indoles ( jstor )
Phosphates ( jstor )
Phosphorus ( jstor )
Soil interactions ( jstor )
Soil samples ( jstor )
Soil science ( jstor )
Soils ( jstor )
Corn -- Kenya ( lcsh )
Dissertations, Academic -- Soil Science -- UF
Eucalyptus -- Kenya ( lcsh )
Plant-soil relationships -- Kenya ( lcsh )
Soil Science thesis Ph. D
Soils -- Kenya ( lcsh )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Thesis (Ph. D.)--University of Florida, 1981.
Bibliography:
Bibliography: leaves 192-204.
General Note:
Typescript.
General Note:
Vita.
Statement of Responsibility:
by Joseph Kipkorir A. Keter.

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GROWTH AND COMPOSITION OF EUCALYPTUS AND MAIZE ON KENYA SOILS FERTILIZED WITH PHOSPHATE AND INDOLE ACETIC ACID








BY

Joseph Kipkorir A. Keter


A DISSERTATION PRESENTED TO COUNCIL OF THE UNIVERSITY IN PARTIAL FULFILLMENT OF THE FOR THE DEGREE OF DOCTOR OF


THE GRADUATE OF FLORIDA REQUIREMENTS
PHILOSOPHY


UNIVERSITY OF FLORIDA


1981














ACKNOWLEDGMENTS

I wish to express my deep indebtedness to Dr. J. G. A. Fiskell, the chairman of my supervisory committee, for his kind advice and guidance in my research. I also thank Drs. V. W. Carlisle, H. L. Popenoe, W. L. Pritchett, D. F. Rothwell, and P. V. Rao members of my supervisory committee for their helpful suggestions in this study.

I express my special thanks to Rebecca Peck and Dr. F. G. Martin for their helpful evaluation of the data.

I gratefully acknowledge the assistance and help I got from Frank Sodek, Dave Cantlin, Mary McLeod, Craig Reed, and Lee Jacobs for some of the laboratory assistance.

I acknowledge Patricia Liebich for typing this dissertation.

I thank my wife, Mary, for her support and sacrifices during the tenure of this study, and to my daughter Winnie for making our stay here joyful.


ii













TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS.......................................... ii

LIST OF TABLES............................................ v

ABSTRACT.................................................. xv

INTRODUCTION.............................................. 1

LITERATURE REVIEW......................................... 7
Phosphorus.............................................. 7
Occurrence of Phosphate Minerals.................... 7
Inorganic Phosphorus in Soils....................... 7
Reactions of Phosphorus in Soil...................... 9
Adsorption Reactions................................ 11
Movement of Phosphate Ions in Soil................. 13
Mechanisms Affecting Ion Distribution............. 17
Effectiveness of Phosphate Fertilizers............ 22
Pelletized Phosphate................................. 24
Phosphate Placement.................................. 25
Fluid Fertilizers................................. 29
Residual Phosphorus in Soils........................ 30
Maize .................-................................ 33
Utilization of Phosphorus............................ 33
lbsearchin Kenya..................................... 34
Indole Acetic Acid in Maize............................. 34
Eucalyptus.............................................. 41
Classification.................................... 41
The Eucalypts Range of Growing Conditions......... 43 Eucalypts as an Exotic Plant....................... 44
Eucalyptus grandis.................................. 45
Site Quality...................................... 6
Fert ilizers......................................... 47
Container-Grown Seedlings........................... 48
Types of containers............................... 49

MATERIALS AND METHODS..................................... 51
Soil Properties........................................ 51
Soil Preparation..................................... 52
Eucalyptus Experiment................................ 53
Maize Experiment after Eucalyptus..................... 54
Maize Experiment with Two Soils....................... 54
Analytical Methods..................................... 55
Reagents for P Determination........................ 56
Soil Extraction................................... 57


iii











Page


Extraction of Plant Tissue........................... 58
P Determination..................................... 59
Statistical Analysis................................ 60

RESULTS AND DISCUSSION.................................... 62
Eucalyptus Experiment.................................. 62
Sols................................................ 62
Growth Factors...................................... 62
Maize Experiment after Eucalypt........................ 91
Growth Factors....................................... 91
Maize Experiment with Two Soils, Athi and Kabete,
Treated with Fresh CSP and lAA........................ 110
Growth Factors.................................... 110

REGRESSION RELATIONSHIPS.................................. 124
(i) Eucalyptus Experiment........................... 125
(ii) Maize, Residual Soil Treatments................. 127
(iii) Maize, New Treatments........................... 128

CONCLUSIONS............................................... 130

APPENDIX.................................................. 133

LITERATURE CITED.......................................... 192

BIOGRAPHICAL SKETCH....................................... 205


iv












LIST OF TABLES


Table Page
1 Some properties of soils from Kenya .................. 63

2 Means and significant height responses for
Eucalyptus grandis grown on three soils treated
with 1AA and CSP ......................................65

3 Soil x treatment means for CSP forms x rate
quadratic effects found for eucalypt height at
2 months ............................................. 67

4 Interaction of soils for 1AA and CSP comparison
for eucalypt height at three times ....................68

5 Mean effect of soil depth on eucalypt height in
response to lAA and CSP alone ........................ 69

6 Interaction of soils on comparison of mean
eucalypt height for CSP with 1AA (CSP-lAA) and
CSP+1AA .............................................. 70

7 Interaction of soil depths on comparison of mean
eucalypt height for CSP-lAA and CSP+1AA ................7

8 Mean effect of soils on eucalypt height, comparing 72
controls with the other treatments ...................

9 Mean effect of soil depth in eucalypt height on
control compared to other treatments ................. 73

10 Means and significant stem diameter, weight of
tops, and tops P of Eucalyptus grandis grown on
three soils treated with 1AA and CSP .................

11 Interactions of soils with response of eucalypt
tops P to CSP rates .................................. 79

12 Interactions for soils with response of eucalypt
stem diameter, tops weight, and tops P for comparison
of mean CSP and lAA treatments ........................81

13 Interactions for soil depths on response of eucalypt
stem diameter, tops weight, and tops P for comparison 82
of mean CSP and lAA treatments .......................


V










Table Page
14 Interactions of soils with response of eucalypt stem diameter, tops weight and tops P for comparison of
mean CSP-lAA and CSP plus lAA treatments............... 83

15 Interactions for soil depths on response of eucalypt stem diameter, tops weight, and Lops P for
comparison of mean CSP-lAA and CSP plus 1AA
treatments................................................ 84

16 Interaction of soils with response of eucalypt stem
diameter, weight of tops, and tops P for comparison
of control with other treatments......................... 85

17 Means and significant responses for leaf P (in two
soils) of Eucalyptus grandis and soil test P by DA and SB methods for three soils treated with 1AA and
CSP ......................................................... 88

18 Interaction of soils on mean DA-P values for linear
response to CSP treatments for eucalypt.................. 90

19 Interaction of soil depth with DA-P extracted from
soils for eucalypt for CSP form comparison............. 90

20 Interactions of soils on DA-P and SB-P for treatment
comparison of CSP with 1AA for soils used for
eucalypt.................................................. 92

21 Means and height of Zea mays responses to residual
1AA and CSP applied to three soils....................... 94

22 Interaction of soils with maize height at 4 weeks
for comparison of linear response to CSP rates......... 96

23 Interaction of soils with maize height at 4 weeks
for comparison of I Inear re-ponHe to CSP-IAA rates..... 9

24 Interaction of sol s with maize height at 6 weeks for
comparison of response to CSP and lAA alone............ 96

25 Interaction of soil depths on maize height at 6 weeks
comparing linear response to CSP-lAA rates............. 99

26 Interaction of soils on maize height at 6 weeks
comparing CSP with lAA treatments al6ne.................. 99


vi











Table Page
27 Means and responses of tops weight and tops P
of Zea mays and of soil test (DA) P to residual
lAA and CSP treatments of three soils ............... 100

28 Interaction of soils with maize tops weight for
comparison of CSP forms ............................. 102

29 Interaction of soils with maize tops weight, tops
P, and DA-P for comparison of linear effect of
CSP rates ........................................... 102

30 Interaction of soils on maize tops weight, tops P,
and DA-P for linear response to CSP-lAA rates ....... 105

31 Interaction of soils on maize tops weight, tops P,
and DA-P for comparison of CSP and 1AA alone ........ 106

32 Interaction of soils on maize tops weight, and
DA-P for comparison of CSP-lAA and CSP+1AA
treatments .......................................... 107

33 Interaction of soils on maize tops weight, tops P,
and DA-P for comparison of control with the other
treatments .......................................... 107

34 Interaction of soil depths on DA-P extracted for
comparison of CSP forms ............................. 108

35 Interaction of soil depths on DA-P extracted for
comparison of linear response to CSP forms .......... 108

36 Means and significant responses for Zea mays
height during 6 weeks grown on two soils treated
with 1AA and CSP .................................... il

37 Interaction of soils on maize height at 4 and 6
weeks for comparison of CSP to lAA treatments alone.. 113

38 Means and significant yield and tissue P responses
for Zea mays grown on two soils treat with lAA
and CSP ............................................. 115

39 Interaction of soils on maize tops yield and tops P
for comparison of linear effect of CSP rates ........ 116

40 Interaction of soils on maize tops for comparison
of linear effect of CSP'lAA rates ................... 116


vii











Table Page
41 Interaction of soils on maize tops P for
comparison of CSP and 1AA treatments ................. 116

42 Interact[on of soils on maize tops P for
cumparLson A1 oLher LreaLmenLa wllh Lhe conLrol ...... 118

43 Interaction of soils on maize leaf P for comparison
of CSP forms - -- --......................................... 118

44 Means and responses of root weight, and root P of
Zea mays and of double acid-extractable soil P for
two soils receiving three rates of IAA and CSP
sources -- --.............................................. 121

45 Interaction of soils on maize root P for comparison
of linear effect of CSP rates ........................... 122

46 Interaction of soils on maize root P and DA-P for
comparison of linear effect of CSP 1AA rates ......... 122

47 Interaction of soi1s on maize root P for comparison
of CSP with 1AA treatments ............................. 123

48 Interaction of two soils on DA-P extracted in the
maize experiment for cdmparison of quadratic effect
of CSP rates ............................................ 123

49 Correlation between yields and corresponding plant
and soil P values ....................................... 124

50 Mean height and stem thickness of eucalyptus
grown on 0- to 15-cm depth of Athi soil treated
with indole acetic acid (lAA) and three concentrated
superphosphate (CSP) sources at three rates........... 133

51 Mean height and stem thickness of eucalyptus grown
on 15- to 30-cm depth of Athi soil treated with indole
acetic acid and three concentrated superphosphate
sources at three rates................................... 134

52 Mean height and stem thickness of eucalyptus grown on
0- to 15-cm depth of Mwea soil treated with indole
acetic acid and three concentrated superphosphate
sources at three rates................................... 135


viii










Table Page
53 Mean height and stem thickness of eucalpytus grown on
15- to 30-cm depth of Mwea soil treated with indole
acetic acid and three concentrated superphosphate
sources at three rates.....................................136

54 Mean height and stem thickness of eucalyptus grown on 0- to 15-cm depth of Kabete soil treated with indole
acetic acid and three concentrated superphosphate
sources at three rates.....................................137

55 Mean heighL and sLem tLickness of eucalyptus grown on 15- to 30-cm depth of Kabete soil treated with indole
acetic acid and three concentrated superphosphate
sources at three rates....................................138

56 Mean dry matter yield of eucalyptus tops from eucalyptus grown on three Kenya soils sampled at two depths and
treated with indole acetic acid (lAA) and three
concentrated superphosphate (CSP) sources at three rates..139

57 Mean analysis of eucalyptus tops sampled from 0- to 15-cm depth of Athi soil treated with indole acetic acid and
three concentrated superphosphate sources at three rates..140

58 Mean analysis of eucalyptus tops sampled from 15- to 30-cm depth on Athi soil treated with indole acetic acid and
three concentrated superphosphate sources at three rates..141

59 Mean analysis of eucalyptus tops sampled from 0- to 15-cm depth of Mwea soil treated with indole acetic
acid and three concentrated superphosphate sources
at three rates..............................................142

60 Mean analysis of eucalyptus tops sampled from 15- to 30-cm depth of Mwea soil treated with indole acetic
acid and three concentrated superphosphate sources
at three rates..............................................143

61 Mean analysis of eucalyptus tops sampled from 0- to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at
three rates................................................144

62 Mean analysis of eucalyptus tops sampled from 15- to 30-cm depth of Kabete soil treated with indole acetic
acid and three concentrated superphosphate sources
at three rates.............................................145


ix











Table Page
63 Mean analysis of eucalyptus leaves sampled from
eucalyptus trees grown on the 0- to 15-cm depth
of Mwea soil treated with indole acetic acid and
three concentrated superphosphate sources at
three rates........................................... 146

64 Mean analysis of eucalyptus leaves sampled from eucalyptus trees grown on the 0- to 15-cm depth
of Kabete soil treated with indole acetic acid
and three concentrated superphosphate sources
at three rates........................................ 147

65 Mean analysis of 0- to 15-cm depth of Athi soil sampled after eucalyptus growth treated with
indole acetic acid (lAA) and three concentrated
superphosphate (CSP) sources at three rates.......... 148

66 Mean analysis of 15- to 30-cm depth of Athi soil sampled after eucalyptus growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates................................ 149

67 Mean analysis of 0- to 15-cm depth of Mwea soil sampled after eucalyptus growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates................................ 150

68 Mean analysis of 15- to 30-cm depth of Mwea soil sampled after eucalyptus growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates............................... 151

69 Mean analysis of 0- to 15-cm depth of Kabete soil
sampled after eucalyptus growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates................................ 152

70 Mean analysis of 15- to 30-cm depth of Kabete soil sampled after eucalyptus growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates................................ 153

71 Mean analysis of 0- to 15-cm depth of Mwea soil sampled after eucalyptus growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates................................ 154


x





xi


Table


72 Mean analysis of 15- to 30-cm depth of Mwea soil sampled after eucalyptus growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates ................................ 155

73 Mcon height of maize grown on 0- to 15-cm depth of
undisturbed Athi soil with treatments previously
used for eucalyptus .................................... 156

74 Mean height of maize grown on 15- to 30-cm depth
of undisturbed Athi soil with treatments previously
used for eucalyptus ................................... 157

75 Mean height of maize grown on 0- to 15-cm depth of
undisturbed Mwea soil with treatments previously
used for eucalyptus ................................... 158

76 Mean height of maize grown on 15- to 30-cm depth of
undisturbed Mwea soil with treatments previously
used for eucalyptus..................................... 159

77 Mean height of maize grown on 0- to 15-cm depth of
undisturbed Kabete soil with treatments previously
used for eucalyptus..................................... 160

78 Mean height of maize grown on 15- to 30-cm depth of
undisturbed Kabete soil with treatments previously
used for eucalyptus .................................. 161

79 Mean dry matter yield of maize tops grown on Kenya
soils undisturbed after treatments previously used
for eucalyptus....................................... 162

80 Mean analysis of maize tops sampled from 0- to 15-cm
depth of undisturbed Athi soil with treatments
previously used for eucalyptus......................... 163

81 Mean analysis of maize tops sampled from 15- to
30-cm depth of undisturbed Athi soil with treatments
previously used for eucalyptus......................... 164

82 Mean analysis of maize tops sampled from 0- to
15-cm depth of undisturbed Mwea soil with treatments
previously used for eucalyptus......................... 165

83 Mean analysis of maize tops sampled from 15- to
30-cm depth of undisturbed Mwea soil with treatments
previously ysed for eucalyptus......................... 166


Page











Table Page
84 Mean analysis of maize tops sampled from 0- to 15-cm
depth of undisturbed Kabete soil with treatments
previously used for eucalyptus......................... 167

85 Mean analysis of maize tops sampled from 15- to
30-cm depth of undisturbed Kabete soil with treatments
previously used for eucalyptus.......................... 168

86 Means and treatment comparisons for various elements in tops of Zea mays grown on three soils having
residual IAA and CSP treatments........................ 169

87 Mean analysis of 0- to 15-cm depth of Athi soil sampled after maize growth on undisturbed soil
containing prior treatments for eucalyptus............ 170

88 Mean analysis of 15- to 30-cm depth of Athi soil sampled after maize growth on undisturbed soil
containing prior treatments for eucalyptus............ 171

89 Mean analysis of 0- to 15-cm depth of Mwea soil sampled after maize growth on undisturbed soil
containing prior treatments for eucalyptus............ 172

90 Mean analysis of 15- to 30-cm depth of Mwea soil sampled after maize growth on undisturbed
soil containing prior treatments for eucalyptus....... 173

91 Mean analysis of 0- to 15-cm depth of Kabete soil sampled after maize growth on undisturbed soil
containing prior treatments for eucalyptus............ 174

92 Mean analysis of 15- to 30-cm depth of Kabete soil sampled after maize growth on indiiturbed
soil containing prior Vrntmeintm for eueilypltu.......... 175

93 Mean and treatment comparisons for various elements
extracted by DA reagent from three soils with residual
IAA and CSP treatments, sampled after Zea mays
harvest.................................................. 176

94 Mean height of maize grown on 0- to 15-cm depth of Athi soil treated with indole acetic acid and
three concentrated superphosphate sources at three
rates.................................................... 177

95 Mean height of maize grown on 0- to 15-cm depth of Kabete soil treated with indole acetic acid
and three concentrated superphosphate sources at
three rates.............................................. 178


xii











Table Page
96 Mean dry matter yeild of maize tops and roots from
maize grown on 0- to 15-cm depth of Athi and Kabete
soils treated with indole acetic acid and three
concentrated superphosphate sources at three rates..... 179

97 Mean analysis of maize tops sampled from 0- to 15-cm depth of Athi soil treated with indole acetic
acid and three concentrated superphosphate sources
at three rates........................................... 180

98 Mean analysis of maize tops sampled from 0- to 15-cm depth of Kabete soil treated with indole acetic acid
and three concentrated superphosphate sources at
three rates.............................................. 181

99 Significant factors of the analysis of variance for maize tops responses to two soils treated with 1AA
and CSP................................................ 182

100 Mean analysis of maize leaves sampled from maize
grown on the 0- to 15-cm depth of Athi soil treated
with indole acetic acid and three concentrated
superphosphate sources at three rates.................. 183

101 Mean analysis of maize leaves sampled from maize
grown on the 0- to 15-cm depth of Kabete soil
treated with indole acetic acid and three
concentrated superphosphate sources at three rates..... 184

102 Significant factors of the analysis of variance of
maize leaf responses to two soils treated with 1AA
and CSP.................................................. 185

103 Mean analysis of maize roots sampled from maize
grown on the 0- to 15-cm depth of Athi soil treated
with indole acetic acid and three concentrated
superphosphate sources at three rates.................. 186

104 Mean analysis of maize roots sampled from maize
grown on the 0- to 15-cm depth of Kabete soil
treated with indole acetic acid and three
concentrated superphosphate sources at three rates..... 187

105 Significant factors of the analysis of variance of
maize root responses to two soils treated with lAA
and CSP.................................................. 188

106 Mean analysis of 0- to 15-cm depth of Athi soil
sampled after maize growth treated with indole
acetic acid and three concentrated superphosphate
sources at three rates.................................. 189


xiii












Table Page
107 Mean analysis of 0- to 15-cm depth of Kabete soil after maize growth treated with indole acetic acid
and three concentrated superphosphate sources at
three rates............................................. 190

108 Significant factors of the analysis of variance for eucalypt tops in response to three soils treated
with 1AA and CSP....................................... 191


xiv














Abstract of Dissertation Presented to the Graduate
Council of the University of Florida in Partial Fulfillment
of the Requirements for the Degree of Doctor of Philosophy



GROWTH AND COMPOSITION OF EUCALYPTUS AND MAIZE ON KENYA SOILS FERTILIZED
WITH PH1OSPHATE AND INDOL ACETIC ACID By

Joseph Kipkorir A. Keter

August, 1981

Chairman: John G. A. Fiskell Major Department: Soil Science

Three glasshouse experiments were conducted with three Kenya soils to determine plant responses to exogenous indole acetic acid (lAA) at 31, 62, and 124 g/ha and to concentrated superphosphate (CSP) in powder, pellet, or pellet (including 1AA) forms applied at 28, 56, and 112 kg P/ha. Soils were taken from depths of 0 to 15 and 15 to 30 cm and two soils were Vertisols (Athi and Mwea) and the other a Latosol (Kabete). The soils were nearly similar in pH (6-3 to 6.8) but differed in soil test P by the double-acid method (DA-P) with values of 4-5, 7-0, and 550 ppm P for Athi, Kabete, and Mwea soils,

respectively. Soil test for P by 0-5 N sodium bicarbonate (SB-P) was also used for Athi and KabcLe soils.

Eucalyptus grandis was planted in the first experiment and early growth exhibited purplish leaves and stems on Athi and


xv












Kabete soils, particularly without P added, attributed to P deficiency. At 2, 3, and 4 months, height of plants was greater where CSP was ised comp;ired to ],AA ;id differed between soils. Tops weight, stem diameter, and tops P were significantly greater where CSP was present but only tops P increased with the amount of CSP Forms applied. For each soil, high ly sigi ificant linear regressions were obtained between tops P and either DA-P or SB-P, tops P and leaf P, and DA-P and SB-P. Fertilization with 28 kg P/ha resulted in tops P or leaf P above 0-110%.

On the above soils left undisturbed, Zea mays L. of cultivar 'Pioneer 3160' was planted. Plant height, tops weight, and tops P increased linearly with previous CSP rates and were lower for

IAA. Highly significant linear regression relationships were found between tops P and DA-P for each soil and at each soil depth. Another study with maize after preplant fertilization of Athi and Kabete soils showed that root weight was higher where CSP was present and root P was less than leaf P or tops P.


xvi













INTRODUCTION

The greatest challenge facing most developing countries,

especially those in tropical Africa, is the ability to (i) produce enough food for its people, and (ii) control the population growth. These countries have numerous other problems such as unstable governments, inadequate health care, too much dependence on foreign countries for most of the manufactured goods, high illiteracy, and failure to make full and wise use of the available natural resources.

Agricultural production in the tropics is principally

controlled by rainfall, for in equatorial regions the temperature is fairly constant over the year. In most areas, the rainfall is never uniformly distributed throughout the year. Near the equator there are typically two rainy seasons a year.

The outstanding characteristic of the rainfall over most of tropical Africa from the agricultural point of view is that, averaged over the year, it is less than the amount of water a crop well-supplied with water would transpire. It is, therefore, necessary to restrict crop production to the rainy seasons or choose crops which will not suffer too severely if subjected to considerable periods of drought.

Agricultural production in the tropics can be intensified

by (Ivve I II)ng ImVLhOdIH o[r eosurI iig Ihe Ih e,;t tite of ra In that fa I Is on thu land. These me1tihods can be groutipd Into tlireC categories: foremost are those which enusre that as much as possible of the


1






2


rain percolates into the soil, at least up to the amount the growing crop needs for a good yield. Secondly, those methods involving the choice of a crop and its management are needed so that its yield is as high as possible from the water that is actually available. Thirdly, there are those methods in which a crop is chosen and managed in order to minimize the harmful effects of drought during its growing season. These methods will not be considered in detail here but were only mentioned in order to specify further the agricultural problems of semi-arid areas of the tropics.

Semi-arid areas are not characterized by low rainfall every year, so that, in a certain proportion of years in these areas, crop yields are more influenced by the level of soil fertility than by the availability of water.

In most areas phosphate and nitrogen are the nutrients most likely to limit crop yields. In many areas of tropical Africa, the soils appear to be very low in phosphate, and crops usually respond well to phosphate fertilizers. It is now well-established that a phosphate fertilizer applied to a soil low in phosphate will increase yields for a number of years after application.

Effectiveness of P fertilizers is dependent upon chemical and physical characteristics of the fertilizer, rate of its use, and method of its application. Soil and climatic conditions under which the crop is grown, and crop characteristics also influence the effectiveness of P fertilizer.






3


Phosphorus fertilizers can be classified into three groups on the basis of their solubilities, namely: (i) those in which the P is mostly soluble in water, (ii) those not readily soluble in water but solub.1c in ammonium citrate, and (iii) those insoluble in ammonium citrate. Usually, the sum of (i) and (ii) represents the so-called available P.

It is found highly desirable to granulate fertilizers in

order to facilitate handling and application and, possibly, also influence the agronomic value of the fertilizer in some cases. Granule size may influence fertilizer effectiveness in two ways. First, it affects the placement pattern or distribution of fertilizer in the soil; and second, it determines the effective surface area and the reactivity of the material.

Reaction of P with the soil to form largely insoluble products is less likely to be a limiting factor than rate of P dissolution in the case of slightly water-soluble P fertilizers. Consequently, small granules which provide a large surface area and ensure closer contact with and better distribution through the soil are

generally assumed to be more effective than large granules. But in the case of highly water-soluble phosphates, rate of dissolution generally is of less concern than reversion or reaction with the soil to form less soluble compounds. The rate of P reaction with the soil tends to be less with large than with small granules.

Another factor that is important in considering water

solubility and granule size relationships is method of application





4


of the fertilizer. Banding of the fertilizer tends to minimize contact and reaction with the soil. The zone of diffusion around a band becomes an enlarged version of the zone around a coarse granule. Such application tends to accentuate the value of a high degree of solubility. Broadcasting the fertilizer and mixing it with the soil maximizes fertilizer and soil reaction and favors the less soluble sources.

The study of growth control mechanisms is one of the most

active fields of plant physiology. It is now evident that growth is controlled not by one but by several groups of hormonal substances as well as by numerous naturally occurring inhibitors which are still very Incomplete.1y understood. Tiiformat IonW oni IndoLe aceL ic acid (1 AA), one o Lhe mosL w.Iduly sLuidLed subsLances, shows that it is produced mainly in meristematic and growing regions of shoots; senescent tissue has also been suggested. lAA is found in most tissues. It moves readily from shoots to roots in phloem and more slowly by cell to cell by polar-transport, basipetally in shoots and acropetally in roots. lAA promotes

e lollp.'t lol of titow 'lllad co l-opt ile!4, 1111 nd P'ool rop l curvature, adventitious rooting and lateral root initiation, xylem differentiation, fruit growth, cambium activity and leaf epinasty. However, it can inhibit root elongation, leaf senescence and fruit abscission.

Production of lAA is inhibited by Zn and P deficiencies and increased by gibberellins and cytokinins.











In maize crops, there is a close relationship between

high-producing varieties, fertilizer, plant population and moisture condition of the soil. Another extremely important factor, particularly under African conditions is early planting, which means planting at the start of the rains. In Kenya, it has been found that planting after the rain has started causes significant reduction in yields. The actual size of the reduction in yield will vary according to such circumstances as the rainfall pattern and the soil characteristics. If the rainfall is not very heavy, and the soil has good structure and drains quickly, then the decline in yield from late planting will be smaller than if the rainfall is heavy, and the soil has poor structure and drainage. For that reason, intensive soil cultivation with the ploughing in of maize stover, is. practiced where possible, in order to improve soil structure, and good soil drainage which are of the utmost importance.

Phosphorus promotes the development of the root system,

aids in seed formation and hastens ripening of maize. The maize plant has a coarse, fibrous root system which spreads widely and penetrates deeply. Nevertheless the young plant has difficulty in taking up phosphorus from the less available phosphate forms in the soil. Maize is, therefore, often used as a test-plant to estimate the amount of easily available P in a soil. In order to stimulate early growth and development care should be taken to provide the crop with a sufficient amount of easily avaliable P.




6


The need to stimulate modern agriculture is urgent in Africa because the population is increasing at a faster rate than is food production. Most African countries import paper and yet they could produce trees such as eucalypt for their timber and paper needs. Cost of importing fertilizer and lack of capital restricts improvement of crop yields. There is need to use P fertilizers efficiently and effectively. If a method could be found to stimulate rooting of seedlings and early plant growth, this might also increase the efficiency of applied P by causing more root intercept of available P.

The present study was done with three Kenya soils in order to test if indole acetic acid could assist in improving the response of two test crops to P fertilization by stimulating root proliferation and plant growth. To check this hypothesis, pelletized CSP was made containing 100 ppm of indole acetic acid (IAA). The experiments consisted of three rates of CSP containing IAA compared to IAA without P. The effect of pelletized CSP without IAA was compared to CSP in powder form to be determine if pelletized CSP caused a different plant response. The first experiment was conducted with Eucalyptus grandis using three rates of IAA, and three rates of three CSP sources to check on the response to IAA and to pelletized P. The objective of the second experiment was to test for residual effects of CSP and IAA on Zea mays grown on these soils. The third objective was to determine if CSP and IAA or in combination applied preplant had an effect on maize responses.














LITERATURE REVIEW

Phosphorus

Occurrence of Phosphate Minerals

Phosphate minerals form under a wide variety of environmental conditions ranging from silicate melts, to natural soils, to ocean floors. In nearly all naturally occurring phosphates, P is pentavalent, even though tri-, quadri-, and hexavalent-P compounds are readily synthesized (Lindsay and Vlek, 1977).

X-ray diffraction has made it possible to determine the

crystal structures of most orthophosphates. It was observed that the central P atomi is surrounded by four 0 a totms forminig an approximaLely tetrahedral structure (LLndsay and Vtek, 1977). This configuration is possible because of the formation of four a-bonds after sp3 hybridization and additional H-bonding using d-orbitals. The structural formulas of these compounds are represented as having a double bond in order to satisfy classical valency requirements, but some sharing of the multiple-bond chiairicter occurs ;moug the four 0 iLtmn.

The formation of stable atomic structures containiig 1'O4

tetrahedra is naturally accomplished through the high affinity of P04 for cations, particularly those exhibiting eightfold coordination. Inorganic Phosphorus in Soils

Inorganic phosphorus in soils is believed to exist as sparingly soluble orthophosphates of Al, Fe and Ca. The Ca-P compounds such


7






8


as apatites are of primary origin. Al- and Fe-P, such as variscite (AlPO4-2H20) and strengite (FePO4-2H20) are generally believed to be the predominating ultimate end-products of inorganic P formed during soil genesis and P fertilization (Chakravarti and Talibudeen, 1962; Chang and Chu, 1961; Chang and Jackson, 1958; Hawkins and Kunze, 1965; Kittrick and Jackson, 1956; Lindsay et al., 1959; Taylor et al., 1963; Yuan et al., 1960). Soil test correlation studies have shown that, in acid soils, the Al-P fraction as determined by Chang and Jackson's procedure (1957) is more available to upland crops than the Fe-P fraction. There is evidence that the Ca-P fraction is the least available of the three fractions (Chang and Juo, 1963; Hanley, 1962; Payne and Hanna, 1965; Susuki et al., 1963; Smith, 1965).

In soil, most of the inorganic P occurs in the clay fraction

from which it cannot be separated by physical methods (Larsen, 1967). Consequently, direct evidence of the nature of the inorganic P cannot be obtained by known petrographic methods. Only when P has been separated from the soil (or formed in layers or pockets in the soil by natural processes) can a sufficient concentration of P minerals be obtained for direct petrographic examination. So far, only the P minerals apatite, vivianite (Fe3(PO4)2'8H20) and wavellite (A13(OH)3(PO4)2*5H20) have been qualitatively determined in soil by such methods (Black, 1957).

A semiquantitative method for the direct determination of

soil apatite was developed by Shipp and Matelski (1960). Although this method provides a direct way of detecting apatite minerals,





(9


it does not distinguish between the various forms of apatite, such as fluoroapatite and hydroxyapatite.

Chang and Jackson (1957) attempted to classify inorganic

soil P into different fractions, according to their extractability in various reagents. Since the reagents are very likely to cause a redistribution of the phosphorus during the extraction, such methods must be arbitrary. In view of this, the compounds reported to be in the soil may not have been actually present in the original soil.

Reactions of Phosphorus in Soil

Lehr and Brown (1958) and Lehr et al. (1959) identified

CaHP042H20 (dicalcium phosphate dihydrate), CaHPO4 (dicalcium phosphate anhydrous), Ca4H(PO4)3-3H20 (octocalcium phosphate), and apatite in soils following the application of superphosphate. The particular compounds formed depended upon soil properties. Moreno et al. (1960a, 1960b) determined the solubility and stability of dicalcium phosphate dihydrate and octocalcium phosphate.

Cole and Jackson (1950, 1951) made preparations of AlP04-2H20 (variscite), FePO4-2H20 (strengite) and other compounds and hypothesized their probable formation in soils was as phosphate fixation products. Haseman et al. (1950, 1951) showed that under certain conditions complex crystalline phosphates of iron and aluminum were formed when clays or iron and aluminum oxides reacted with phosphate solutions. Kittrick and Jackson (1955) reacted soil minerals with phosphate solutions and, by use of the electron microscope, presented evidence of the formation of new P, crystalline phases.






10


Lindsay and Stephenson (1959) repeatedly reacted a series

of soil samples, first with a solution saturated with respect to Ca(H2P04)2-H20 (monocalcium phosphate monohydrate) and CaHPO42H20 (MTPS, that is, metastable triple-point solution), and later with water, in an attempt to simulate the changing chemical environment of soil surrounding a superphosphate granule. They found that the reaction of MTPS with soil was accompanied by an increase in pH and precipitation of Fe, Al, and Ca phosphates from solution. Soil repeatedly contacted by MTPS gradually became more acidic and showed continued dissolution of Fe and Al. Subsequent additions of water to the soil residues remaining after reaction with MTPS increased the pH and caused further precipitation of phosphate from solution. Many filtrates obtained during these reactions yielded precipitates upon standing. They identified the following crystalline compounds from these precipitates:

CaHP04.2H20, H6K3Als(PO4)8-18H20
HBK(Al,Fe)3(PO4)6-6H20, and CaHPO4

Lindsay and Stephenson (1959) also suggested that the indications

are that these compounds may form as initial phosphate reaction products of superphosphate fertilizers in soil.

Bell and Black (1970) compared the methods for identifying crystalline phosphates produced by interaction of orthophosphate fertilizers with soil. In soils that were treated with Ca(H2P04)2-H20, NH4H2PO4, and (NH4)2HP04, various methods were investigated. These ranked as follows in decreasing order of

sensitivity:optical examination of soil 2 optical examination of






I I


glass-fiber filter paper inclusion > X-ray diffraction examination of glass-fiber filter paper inclusion > X-ray diffraction examination of soil.

Adsorption Reactions

The reaction of fertilizer P with soil depends upon the nature and amount of adsorbing surface as well as pH and other factors. Olsen and Watanabe (1957) found that adsorption of P by soils from dilute solutions showed a closer agreement with the Langmuir isotherm than with the Freundlich curve. The adsorption maximum calculated from the Langmuir isotherm was closely correlated with the surface area of soils as measured by ethylene glycol retention.

Regression analysis of phosphorus adsorption as a function of five soil characteristics indicated that organic matter is important in the initial bonding of P by soils (Harter, 1969). He proposed that P is initially bonded to anion exchange sites on organic matter, and subsequently transformed into less soluble iron and aluminum phosphates.

Rajan and Fox (1975) studied phosphate adsorption by several

Hawaiian and Indian soils, and the relation of phosphate adsorption to hydroxyl, suLfate, and silicate foiw released in two lanwa lin soils. Adsorption isotherms of some of the soil showed an abrupt

increase in phosphate adsorption at high concentration.

They analyzed the isotherms by applying a binary Langmuir equation (assuming two types of sites). They observed that phosphate adsorption is associated with increased pH and sulfate






12


release at low levels of phosphate adsorbed and increased silicate release throughout. According to Rajan and Fox (1975), these observations suggest that, at low concentrations, phosphate exchanges with (i) adsorbed sulfate and adsorbed silicate, and

(ii) with water and hydroxyls of metal hydrous oxides and edge Al of clays. At high concentrations, additional phosphate is adsorbed by displacing the structural silicate of clays. The increase in phosphate adsorption by structural silicate release, over that of surface exchange reactions, was about 50 and 25% in two soils containing kaolinite and allophane, respectively.

Mekaru and Uehara (1972), using the difference in pH of a soil suspension prepared with 1N KC1 with water to determine net charge of colloids with constant potential type surface, found that the quantity (pHKCl-pHHO2), called delta pH, had a positive, zero, or negative value corresponding to the net surface charge. Negative and positive adsorption of chloride or nitrate ions were measured in soil suspensions with negative and positive delta pH, respectively. They found that increasing the nitrate ion concentration increased sulfate adsorption in suspensions with negative delta pH values. Negative adsorption of nitrate and chloride ions was measured when sulfate ions were added to a soil colloidal suspension which had initially a net positive charge. Their belief that specifically adsorbed anions render a surface more negative by displacing the zero point of charge to lower pH values was supported in their observations.





1L


Furthermore, this was substantiated by a measured increase in cation exchange capacity (CEC) over an initial value of 26 meq/100g in a phosphated soil. Each millimole of adsorbed phosphate increased the soil CEC by 0.8 mcq.

Langmuir plots of P adsorption Isotherms of four soils were shown to fit into two intersecting lines (Taylor and Ellis, 1978). These workers investigated the mechanism of P adsorption on soil and anion exchange resin surfaces at low equilibrium concentrations. The adsorption data were also found to fit the BET (Brunauer, Emmett, and Teller) equation. The monolayer capacities computed from the BET equation were found to correspond closely with the adsorption maxima computed from the initial slopes of the Langmuir plots.

Taylor and Ellis (1978) concluded that, at low concentrations, P was bonded by two points of attachment after deprotonation of the H2P04 ion, followed by one point of attachment at higher P concentrations during adsorption on the resin surface. This resulted in the deviation from linearity predicted by the Langmuir equation.

Movement of_ Phosphiate lolls in Soil.

The mobility of P applied as diammonium orthophosphate (DAP), triammonium pyrophosphate (TPP), or ammonium polyphosphate (APP) was studied by Khasawneh et al. (1974) in columns of a fine sandy loam. They observed dissolution of the fertilizer in soil moisture that moved towards the P-application site. This water movement was sometimes against a gradient in soil moisture content, but it was along a gradient in the total potential of soil water.





1/1


They found that the extent of P movement from all three sources was similar, but that the distribution patterns were different. The extent of P movement was influenced more by the initial soil moisture content than by the source of P. They also noted that a higher fraction of the added P was precipitated when the source was TPP or APP than when it was DAP. The ability of the polyphosphates to sequester soil Fe and Al did not prevent the precipitation of these phosphates nor did it make them more mobile than the orthophosphates. They found APP only delayed the precipitation reaction to a degree that depended on the polyphosphate content of the fertilizer material.

Hydrolysis and sorption of pyro- and poly-phosphates in

soil have been studied by many workers. Sutton and Larsen (1964) and Sutton et al. (1966) measured rates of hydrolysis of pyrophosphates in soil, and found that hydrolysis was largely enzyme-mediated and related to the overall biological activity as measured by C02 evolution. Gilliam and Sample (1968) found that either sterilizing soil by fumigation with CH3Br or by autoclaving did not completely stop hydrolysis, indicating that chemical as well as microbial factors in the soil determine the rate of pyrophosphate hydrolysis. Hashimoto et al. (1969)

reported that hydrolysis ceased when concentration of pyrophosphates in a soil suspension exceeded 0.2M. They also reported that pyrophosphate was adsorbed more strongly than orthophosphate on soils and clay minerals. Sutton and Larsen (1964) had reported just the opposite for soils in England. Their data indicated that





15


ortho-phosphate was adsorbed more strongly than pyrophosphate by soil, but that these soils had higher adsorption capacity maxima for pyrophosphate than for orthophosphate.

Khasawneh et al. (1974, 1979-) discussed the comparative

mobility of ortho- and polyphosphates in soil and related it to two soil processes:(i) reactions of these phosphates with soil, and (ii) biologically catalyzed hydrolysis of the poly-phosphates. In their view, diffusive movement of phosphates away from granule or band sites is basically by salt diffusion where equivalent amounts of cations and phosphatic anions are involved. They reasoned that since fertilizer solution is initially very concentrated in both phosphates and NH4 , subsequently NH4 readily replaces exchangeable cations, such as Ca, Mg, K, and Al. These cations, however, when combined with orthophosphates form salts that are rather insoluble and may be rapidly precipitated in situ in soil, or their precipitation may be delayed to the extent that if the solution phase is separated from the soil, precipitation occurs thereafter (Lindsay et al., 1962).

Lindsay et al. (1962) reported that considerable amounts of soil Fe and Al were dissolved by solutions of ammonium ortho- and polyphosphates, indicating that reaction of concentrated solutions of ammonium phosphates is not limited to exchangeable cations. For example, ammonium polyphosphate solutions dissolved 63 Pmoles of Fe/liter and 8 moles of Al/liter when added to Fe203*H20 and Al(OH)3, respectively. Hashimoto et al. (1969) reported that 25 ml of a 2.OM solution of triammonium pyro-phosphate dissolved









65 mg of Al from gibbsite and 10 mg of Fe from goethite in a 2-day period. They found that similar solutions were much less reactive with kaolinite and montmorillonite.

In a study on the effects of cations associated with reactions of ammonium ortho- and poly-phosphate fertilizers in soil, Sample et al. (1979) found that, in general, the NH4 ions derived from the fertilizer salts moved in association with the phosphate anions in the form of salt diffusion, and also moved by counter diffusion in exchange for some of the exchangeable soil cations. Exchangeable Ca in the first 6 mm of soil contacted by the fertilizer solution from diammonium phosphate (DAP) was
+ 2+
replaced by NH4 , and the displaced Ca2+ was precipitated in place by phosphate. Displaced Ca was transported in the fertilizer solution of triammonium pyro-phosphate monohydrate (TPP) and ammonium polyphosphate (APP) for 6 to 8 mm before it was precipitated. Reactions of phosphates with displaced Ca2+ caused its activity in these soil zones to drop sharply and created a Ca gradient opposite to that of the phosphates. They observed that depletion of exchangeable cations, especially at or just

beyond the fertilizer solution front, caused soil pH1 to drop as much as one pH unit below the initial soil value. Within the soil zone affected by phosphates, pH was about 7.5 with DAP and 6.7 to 7.2 with APP and TPP. Differences in pH between soil in

the outer zones reached by phosphates and the inner layers ranged from 1.7 to 2.7 pH units.


1()










In the study by Sample et al. (1979), it was found that soil Al was influenced greatly by all three fertilizer solutions so that with DAP, the reaction products simply reprecipitated in place without undergoing any movement. The observed increased acid extractability was the only evidence of the presence of fresh precipitates involving Al. They determined that in addition to such a reaction, movement of Al occurred with TPP and APP, and there was evidence of rather--well-defined zones of precipitation involving Al pyro- or polyphosphates. They did not find evidence to implicate Fe in reactions similar to those for Al. Mechanisms Affecting Ion Distribution

Barber (1974b) discussed factors which affect ion movement in soil. Root interception, mass-flow, and diffusion were considered as affecting ion distribution. They measured nutrients as concentration per unit volume of soil when diffusive flow to plant roots was determined. Hence they observed when the bulk density of soil is increased near the root, that the concentration of available nutrients per unit soil volume is also increased. This increase results in a greater concentration gradient for nutrients diffusing to the root (Barber, 1974b). They suggested that roots may also encounter some nutrients and absorb them as it forces its way through the soil.

Oliver and Barber ([966) calculaLed the ions displaced by

the roots as a supply mechanism, although some ions may be pushed away and return to the root by mass-flow and diffusion, they assumed that the amount of ions returning to the root would be in


I/




18


additon to the amount for mass-flow and diffusion. They found that the root did not influence soil bulk density near the root surface.

Barber (1974b) stated that, since plant roots absorb water, tIiy czit m (I: f I ow of wait'r f r()lm th (, I ( t I ie root IIrfl;i(( and this water contains inorganic ions as well as soluble organic molecules. He reported that such ions are mass-transported to the root in the convective flow of the water and that the amount of ions reaching the root depends upon the rate of water flow to the root and the average ion content of this water. He also stated that when the concentration of a given ion at the root surface is reduced, a concentration gradient normal to the root is established because the ion diffuses toward the root due to the thermal motion of the particles. His research indicates that the ion supply to the root and the rate of uptake is largely regulated by the rate of diffusion. He considered that diffusion follows Fick's law, which is F = - DA(3c/Dx),

where F is the amount diffusing per unit of time, t; D is the diffusion coefficicnt; A is the area for diffusion; and Dc/Dx is the concentration gradient. Since diffusion to a root is in radial coordinates, the appropriate equation becomes more complex. A simplified version of this equation was given by Passioura (1963) as F = - A[(C-Co)Dk/ro]

where C is the initial total concentration of the nutrient in the soil; Co is the concentration at the root surface; ro is the root










radius; k is a monotonically decreasing function of Dt/r ; and
0

t is the time that the sink has been operating. He considered that the soil reacts chemically with many of the nutrients that diffuse to the root and also physically makes the diffusion pathway more tortuous.

The value of D in a soil reflects the reduction in rate of diffusion because of the chemical reaction and the increase in tortuosity because of physical factors (Barber, 1974).

Nye (1968) proposed a simple method for calculating the value of D for phosphate ions as follows; D = DlflVl(dCl/dC)


where D1 is the diffusion coefficient of P in free solution (8-9x10 6 cm2/sec); f, the Impedence or tortuosity F;ctor; VI the volumetric water content; and dCj/dC = 1/b which is the reciprocal of the slope of the P adsorption isotherm.

Rate of P diffusion from fertilizer applied at the soil surface was studied by Hira and Singh (1978) using Fick's Law of diffusion. They determined the diffusion coefficient of P from a knowledge of the tortuosity factor and P adsorption isotherm. Phosphorus diffusion coefficient calculated from Nye's equation did not prove suitable at very low or high concentrations of P at the soil surface. The P diffusion coefficient calculated from their experimental data increased linearly with the square root of P concentration applied at the source. They stated that the P diffusion coefficient could be





20


calculated from the equation,
D1Vjfj
D = b

where Q is the material applied uniformly on a surface (mg/cm2). Their predicted P concentration-distance profiles were found to be very close to the experimental. va iles estim ted by employI ig a sectioning technique.

Chien et al. (1980) derived a modified Elovich equation in the form of

Ct = Co -(1/ )ln(auB)-(1/)lnCt

where a and are constants, t is time, and the term Ct and Co are given below. They described the kinetics of dissolution of three phosphate rocks (North Carolina, central Florida, and Tennessee) in three soils (one soil from Florlda and two Niger fan soils). They compared the values of Co, a, and in the equation with the dissolution rates of various phosphate rocks in a given soil or a given phosphate rock in various soils. In this case, Co is the maximum P concentration in the soil solution that a phosphate rock can provide in a soil (Ct is the P concentration at time t).

Chien et al. (1980) found that Co increased as a increased and/or decreased in a given system. They failed to find any significant effect of temperature on the dissolution of phosphate rock in the soil. This implied that P retention by the tropical soils treated with phosphate rock may be much less affected by temperature than when compared with water-soluble P fertilizers such as concentrated superphosphate.






21


In a study of phosphate sorption by acid, sandy soil, Fiskell et al. (1979) measured phosphate sorption by two soils with time using a laboratory batch technique for a range of initial P concentrations in solution. They compared experimental data with results calculated using a two-site sorption-desorption model and found that, for contact times > an hour, they observed that P sorption in both the sandy soils could be described by assuming rapid and slow reversible reactions to occur simultaneously at two separate types of sorption sites. But for contact times < 60 minutes they found that the 2-site model did not describe the P sorption adequately. At the rapid and slow sorption sites, the orders of the forward reactions were fractional and first-order, respectively, with regard to the P concentration in solution. For a given soil, one set of rate coefficient values was sufficient to describe the solution phase concentration of P for several different initial concentrations.

Chien and Clayton (1980) derived a simple modified Elovich equation in the form:

q = (1/S)ln(a)+(1/3)ln t

where q is the amount of phosphate released or sorbed and a and

2 are constants and t is time. They attempted to fit various experimental data reported in literature that failed to conform to a single first order kinetic equation. Using this equation, they successfully described the data as a single straight line that covers the entire span of reaction time. They suggested that it appeared that constants a and may be used for comparison of reaction rates of phosphate release or sorption in different soils.




22


Effectiveness of Phosphate Fertilizers

Terman (1957) reported that for 433 P rate and source experiments in 7 Southeastern states of the Unites States of America, the distributions of the coefficients of variation (CV) (or standard errors per plot in percent) for corn, cotton, legume, legume-grass hay and small grain were similar. It was found that C.V. values were negatively correlated with yield levels for all crops and standard errors per plot were positively correlated with yield for corn and alfalfa but not significantly for cotton and wheat. They noted that there were no consistent interactions between P sources and rates.

Webb et al. (1959) reported on field research dealing with the importance of water solubility of P in fertilizers applied broadcast and plowed under for corn. Highly water-insoluble sources tended to be slightly less effective in a few of these experiments. But their general conclusion was that, on the soils included in the study, the degree of water solubility of the P was not a significant factor in determining the effectiveness of fertilizers applied by this method. All of the experiments in that study happened to be located on acidic or nearly neutral soils, which raised the question of whether similar results would have been obtained on calcareous soils.

In Iater experiments, Webb et a11. (961) conducted five field experiments in which several slightly wa.er-soluble P sources were compared with concentrated superphosphate (CSP) for use in broadcast applications for maize (Zea Mays L.).





23


These tests were located on calcareous soils which tested low in available P. Based on their effect upon the concentration of P in corn leaves and upon corn yields, CSP and dicalcium phosphate

dihydrate were found to be the most effective sources, with the former being slightly superior. Anhydrous dicalcium phosphate, calcium metaphosphate, and a chemical blend of mono- and dicalcium phosphate were of intermediate effectiveness, producing yield increases of about 70 to 80% of that given by CSP. Granular calcium metaphosphate was the least effective source, being about 60% as effective as CSP in promoting yield increases. They concluded that, on calcareous soils, a highly water-soluble source of P, such as CSP, is likely to be more effective in broadcast applications for corn thain are most sli ghtiy Soluble ' sources. They noted however, that other cliarncLeristics of the fert I l izer may be of equal importance in determining their effectiveness.

In growth chamber and field studies with maize, McLean et al. (1965) employed partially acidulated rock phosphate (with H3PO4) to study its effect on the yields and P content of German millet and alfalfa (Medicago sativa L). Growth An the chamber increased

to a maximum at 72 kg P/ha and 20% acidulatlon on one group of soils and continued to increase with application rate and acidulation degree in another group. They did not obtain any appreciable difference with three methods of preparation of 20% acidulated material. Average field corn yield on the five above soils was highest with 20% acidulated material, resulting in marked economic advantage of this material.





24


McLean and Logan (1970) evaluated several phosphates which differed in water solubility as sources of P for plants grown in soils with varying degrees of P retention. They reported that, with relatively low P retention, P content of maize seedlings increased in direct proportion to the P water solubility, but soils with high P retention resulted in content that decreased with increased water solubility of P.

In experiments with maize, Meelu et al. (1977) found that

all P sources at 60 kg P205/ha were equally effective with evidence of luxury uptake of P from water-soluble P sources. All P fertilizers had a residual effect and soil test for P was significantly correlated with yield of successive crops.

Infertile soils were used by Mortvedt and Terman (1978) to grow maize in three greenhouse pot experiments where the soils had received 0-800 mg P/potas CSP, MAP, a 30:70% mixture of CSP and MAP or a 10:90% mixture of CSP and MAP. Responses were greatest for MAP at adequate P levels and occurred at rates much higher than normally recommended for field experiments. Pelletized Phosphate

The main objective of coating granules of water-soluble

phosphates is to reduce fixation of applied P by the soil, thereby increasing its availability for crop growth. Negative results have usually been obtained, however. Terman et al. (1970) reported no response of a first crop of flooded rice to P in S-coated CSP, but the P became available to a second crop after degradation of the coating. Allen and Mays (1971) found that





25


insufficient P was released from S-coated DAP for early growth of forage sorghum (Sorghum bicolor L.) and resulted in lower total yields than did uncoated DAP.

Nicholaidos et al. (1979) compared pelletized ordinary superphosphate (OSP), uncoated CSP, or coated with S and sealant (SCSP) in a Rhodic Paleudult (a Red Bay, fine, sandy loam), previously uncultivated. They obtained the increase in corn grain yield for the first 28 kg P/ha and further response was linear at 200 kg/ha yield for each additional 28 kg/P applied. They found that field response was not significantly different either for P sources or for P placement. They observed no grain yield advantage to blending OSP and SCSP pellets either in the first or third year. Their soil test values and ear leaf P values showed linear responses to rates of applied P. Phosphate Placement

Fertilizer is considered to be broadcast when applied over the entire soil surface. While most fertilizers are applied in this way (with subsequent incorporation) broadcasting may also include topdressing on growing crops. Broadcast P, however, is generally applied prior to planting since the growing plant needs P early in its development.

Acidulated P materials to be broadcast on acid to neutral soils generally do not need to be high in water-soluble P as discussed above. Field data showed that water solubility of broadcast P fertilizer on acid to neutral soils was not important

(Webb and Pesek, 1959). However, water solubility of P fertilizer broadcast on calcareous soils was found to be quite important (Webb et al. 1961).






26


Application of P is needed less frequently if higher rates

of P are used. In a rotation experiment, Barber (1969) broadcast P fertilizer once every 4 years at rates of 98 and 196 kg P/ha over a 16-year period. Both rates were effective in maintaining yields through the fourth year following each application. He concluded that more flexibility in P application is possible without seriously affecting yield, provided that the P is plowed under or mixed deeply into the soil.

Field experiments were conducted at three locations in

Nebraska and one in Illinois by Cihacek et al. (1974) to compare alternative P application techniques for corn. These were chisel-broadcast, chisel placed (at 18- to 20-cm depth), chisel-row band, and moldboard-broadcast. Results of 3 years of experiments showed that the moldboard incorporation of broadcast P was the most effective combination. It was concluded, however, that tillage effects were more important than placement of P.

In field trials on an Oxisol in Brazil, P rate and placement were examined for maize grain yield (Yost, 1978). Their maximum yields were obtained where 560 kg P/ha were initially broadcast and where 140 kg P/ha were broadcast initially followed by consecutive band application of 35 kg P/ha for each crop.

It is usually recommended that for row and band P applications, the P source should be largely in water-soluble form in order to stimulate growth. Webb and Pesek (1958) studied the effect of a range of water-soluble P content from 2 to 100% of the available






27


P placed at 2.5 cm to the side and 4 cm below maize seed planted in 100- by 100-cm hills. Their increase in yield with higher water-soluble P content was quite marked.

In soils of Tanzania, 40 or 80 kg P/ha were applied by

(a) broadcasting on the soil surface after sowing maize, (b) side dressing after sowing, and (c) drilling 2 to 3 cm below seeds in the planting furrow. When they compared unfertilized control grain yield of 2.5 t/ha to those with P placement methods (a), (b), and (c) grain yields increased by 200, 700, and 900 kg/ha, respectively, at 40 kg P/ha. At the higher P rate, method (a) gave yields alike those found for 40 kg P/ha applied by method (b) or (c). They studied interactions between applied N and P using 0, 40, 80, or 120 kg N/ha and 0, 30, 60, 90, or 120 kg P/ha. These maize yields increased linearly with N rate and this effect was enhanced where 60 kg P/ha was applied. Leaf P content increased linearly with increased rates of P supplied alone or with N. (Uriyo et al., 1980).

Bates (1971) summarized the response from selected treatments of 22 field trials in which normal tillage (plowing and disking) was practiced, and in which P and K were plowed down or banded beside and below the seed either as row or starter placement. He reported that, in only 2 out of 22 field experiments in Ontario, did maize yield increases result from starter fertilizer.

In Australia, Rudd and Barrow (1973) found that when

superphosphate was row-placed for wheat, it was about twice as effective as that applied broadcast at seeding. Prummel (1956)





28


found similar results for several crops including maize, and small grains on P-deficient soil in the Netherlands. Welch et al. (1966) investigated the relative efficiency of broadcast versus banded P and reported that banded P for row crops can be more effective than broadcast P at lower rates of application. However, highest yields were obtained with a combination of banded and broadcast P. This agreed with the findings of Barber (1958) for corn that banding alone on low P soils is inadequate and the supplementary broadcast P is needed to reach top yields.

Barber (1974b)introduced the concept of strip application of fertilizer P as a compromise between broadcast and row placement. He found that surface placement of fertilizer in narrow strips before plowing was more effective than either banding or broadcastplowhing treaLment! al.one. Tis rIp apple iat ulo re!;ii tod in 8 to 10% of the plow layer being affected by fertilizer P after plowing.

Little data are available to indicate the effectiveness of surface-applied fertilizer in continuous no-tillage systems of corn production. In one of the few studies with P fertilizers applied to the soil surface for corn production and not incorporated, Singh ct al. (190>) found higher 1) upLkI( from turfnce-appled 1) than P incorporated into the soil.

Surface application of P and K fertilizer to meadow crops

has been more effective than incorporation of the fertilizer in the plow layer prior to establishment (Stanford ot al., 1955). Broadcast applications of P and K fertilizer have also been effective on established meadow crops (Adams et al., 1967; Templeton et al., 1966).









Belcher and Ragland (1972) concluded that if P was

surface-applied in a no-till system, it was equal in effectiveness to P incorporated into the soil. Several workers have shown no-till corn yields to be equal to or higher than those obtained by conventional tillage (Meschler and Martens, 1975; Triplett and Van Doren, 1969). They stated that the P source used for surface application should be largely water-soluble. Fluid Fertilizers

The term fluid fertilizers is usually used to include both

fertilizer solutions and suspensions (Engelstad and Terman, 1980). These workers proposed that, for a valid comparison of fluid and solid fertilizer P, the P should be supplied in the same chemical compounds in both cases and be similarly placed so that they have comparable contact with soil and proximity to developing root

systems.

Lathwell et al. (1960) summarized the results of a number of field experiments conducted to compare P sources in solution and solid form, involving maize, other field crops, and cotton (Gossypium hirsutum L.). They concluded that P in solution form

is as satisfactory as in comparable solLd sources, but is likely to be superior to those solid materials which contain a large proportion of water-insoluble P. They suggested that the price per unit of P applied in the field should be the main criterion in choosing between solid and solution forms of P.

With suspension fertilizers, the P applied is usually quite insoluble. Finely ground phosphate rock for direct application





30


can be applied in suspension form rather conveniently and avoids

dust problems as well. In this way, the material can be applied in finely divided state as it should be for greatest effectiveness (Engelstad and Terman, 1980).

Residual Phosphorus in Soils

The use of optimal amounts of P for intensive cropping

enables most soils to accumulate residual P (Johnson et al. 1969; Olsen et al. 1978). In drier areas where cxt~eisive cereal cropping is pJraicLiced, the soi-Is often remain def IcIent- when annualfertilizer use has been minimal. In Saskatchewan, soil-available P was enhanced by the continued use of 20 kg P/ha or more with wheat in a 3-year rotation (Spratt and McCurdy, 1966). Both Read et al. (1977) and Bailey et al. (1977) found that large amounts of P (100 to 400 kg P/ha) incorporated in the soil could support cropping on Chernozem soils for several years.

Red soils of the warm and hot humid regions generally have

inherently low levels of available P and high P-fixation capacities. De Datta et al. (1963) found that three latosol soils immobilized over 98% of the added fertilizer P. Woodruff and Kamprath (1965)

found that the Georgeville soil (high in hydrated Al and Fe oxides) had a P-adsorption maximum of 720 kg P/ha, P as calculated from the Langmuir adsorption isotherm. They obtained optimum growth in a greenhouse study with 25% saturation of the P-adsorption maximum.

Band applications of normal rates of phosphate fertilizers have been suggested on red soils for maximum effectiveness of






31


the P. However, Barber (1965) pointed out that band applications of phosphate supply P to plants primarily during the first few weeks of growth. He maintained that for maximum economic yields soils should be high in nutrients throughout the root zone rather

ihan in one spoL.

In a study of the residual effect of large applications of

P on high P fixing (red) soils high in hydrated iron and aluminum oxides, Kamprath (1967) found a marked residual effect of P applied 7 to 9 years beforehand. They found that, even when P was added in the row, corn yields were as much as 50% higher when high rates had been applied 9 years before. This indicated that the P added initially was not irreversibly lost, but was available for plant growth in later years.

The residual value of P in soils depends upon the nature of the compounds formed when phosphate fertilizers react with soil components. Several investigators (Ghani and Islam, 1946; Kaila, 1965; Lavery and McLean, 1961; Robertson et al., 1966; Singh et al., 1966; Volk and McLean, 1963) have reported large

recoveries of P In the AL and Fe form wlicre phosphated soils were subjected to fractionation into the various extractable compounds.

According to Chang and Jackson (1958), calcium and aluminum phosphates are likely to be formed soon after the application of phosphate fertilizers to mineral soils, and as time lapses, iron phosphate would be expected to form. In acid soils, the calcium ion activity may be of such low magnitude that calcium phosphate may not exist at all.





32


Bowman et al. (1978) evaluated four P extraction methods-Olsen-P, Colwell-P, total exchangeable P, and resin-extractable P--in terms of total plant P uptake in a 3-year continuous greenhouse study of 23 calcareous and neutral soils high in P status. All methods were highly correlated with the total P taken up from the soils by 5 to8successive greenhouse crops. They found that the Olsen-P method extracted an average of nearly 50% that of the total plant P, while the Colwell procedure extracted nearly 80% of it. Resin-extractable P and total exchangeable P values approximated the total plant P uptake, and served as good biological measures of the total plant-available P in the soil.





33


Maize

Utilization of Phosphorus

The levels of P availability in soils required for optimum crop production vary among the different crops. Maize is significantly more responsive than soybeans (Glycine max L.) to fertilizer P application, as reported by de Mooy et al. (1973). Another study reported for maize-soybean cropping system, found it was advantageous to apply the P fertilizer for the maize crop (Hanway and Olson, 1980). Similarly, wheat (Triticum aestivum L.) responds to P at higher soil P levels than required for maximum yields for maize, presumably this is related to the fact that wheat makes most of its growth under colder soil conditions than maize (Olsen et al., 1962). Some examples of the effects of certain P sources on the growth of maize have been given above.

Terman et al. (1975) found that differences in nutrient absorption between maize hybrids was apparently influenced by genetic effects on growth rates and yield potentials. Herbage yields increased with increasing levels of applied Zn only where 167 ppm P was also supplied. Content of P in the tissue increased in response to the increase in rates of applied P.

Maize grown in glasshouse experimenLts in soLLs from 68

locaLions in southeastern Nigeria responded in dry matter y Lelds to P applied up to 56 kg P/ha (Enwezor, 1977). When available P levels were less than 34 kg P/ha, maize yields responded to applied P at 28 and 56 kg P/ha.










A study by Creamer and Fox (1980) on the toxicity of banded urea or diammonium phosphate to maize showed both banded urea and diammonium phosphate were toxic to maize root growth. They

attributed this to ammonia toxicity which was favored when the initial soil pH was increased and the soil moisture content accumulation had little effect on the root-toxicity symptoms. Research in Kenya

In Kenya, a series of trials at Kitale showed that sowing

date and cultivars were the most important factors affecting maize yields (Allan, 1974). Plant density and weed control were also factors determining yields. It was found that early sowing increased yield of both poorly managed and optimally grown maize.

In another study of the association between altitude,

environmental variables, maize growth and yields in Kenya, Cooper (1979) found that the potential number of maize grains per embryonic primary ear was greatest at low altitude but the final number of grains per ear at harvest was greatest at high altitude. Growth stopped abruptly at 69, 83, and 96 days after tasselling

at low. e im :111d h11P.1 aII Ittud(.!, reo!spec1 Nv ly. Y eIo (! decreased with decreasing altitude and this was closely related to the mean thermal growth rate during the grain initiation period.

Indole Acetic Acid in Maize

Auxin action of indole acetic acid (lAA) in maize has been investigated by many workers. Edwards and Scott (1977) studied











the effect of 1AA on maize root segments in a citrate-phosphate buffer at pH 4 and pH 7. At neutrality, O.lp4 of 1AA promoted cell elongation only briefly whereas at pH 4 the rate was five times greater. They noted that elongation rate for root segments was much less than that for elongation rate of coleoptile segments when exposed to 1AA at pH 6.8. Investigations by Davies et al. (1976) with resin beads containing LAA placed at 0.5, 2, or 5 mm from maize root tips showed that only 10% of the lAA was in the growing zone compared to that at the extreme root tip after 4 hours. They proposed that endogenous LAA could move to the growing zone of the root tip and might unilaterally inhibit growth if it was in the transport pool as exogenous lAA. Other studies by Naqvi (1976) used 14C-2-1AA at 0.05 to 1.6 mg/liter on maize coleoptile segments and found that the highest efficiency for absorption and translocation of 1AA was when the applied 1AA was from 0.2 to 0.4 mg/liter. Research by Pernet and Pilet (1976) with lAA applied to maize root caps showed that the 1AA entered the root

tip and moved basipetally inside the cap and they concluded that 1hL p InrI y o I AA re il ted ii very slow rni pi t Ir ru th e Cn-1 to the apex.

The biosynthesis of 1AA in aseptically cultured maize roots in media containing 14C-tryptophan or '4C-iAA was demonstrated by Feldman (1980). He reported that exogenously supplied 1AA was rapidly and completely metabolized by root tissues and that the root apex was the main site for synthesis of IAA. This was





36


shown by 1AA continuing to be synthesized at the apex after the root cap and quiescent center were removed from the apex. The level of lAA of roots grown in this medium appeared to be precisely controlled by the roots. In maize cultivars resistant to low temperatures, Zaric (1978) found that the 1AA content of the coleoptile was higher at 25*C than at 1*C but this effect was reversed with cultivars susceptible to low temperatures. They found that at the 3-leaf stage, lAA content was the same for the two sets of cultivars. Myo-inositol esters of IAA were applied to cuts in maize endosperm and were shown to be transported at 400 times the rate of transport of 1AA in studies by Nowacki and Bandurski (1980). They suggested that free 1AA may be lnmi t hig for pIIIIL growLt si nce e.ti r f * 1cat loln of IAA occurred in the shoot and not in the endosperm.

Other workers have found that accumulation of lAA by maize

coleoptile sections was pH-dependent (Edwards and Goldsmith, 1980). They noted that a short-term uptake of lAA in the sections was increased as the buffer p11 was decreased. They observed that tissue cells at pH 5 retained mobile 1AA at several times the concentration of the external lAA. A model for the effect of 1AA on growth of maize coleoptiles was proposed by Darville et al. (1979) and included proton release by 1AA, cell wall structure, and elongation growth.

Maize roots were found to showgrowth inhibition to applied 1AA until the endogenous concentrations of lAA was reduced by





37


exodiffusion so that both root growth and geotropism may interact with the balance of exogenous and endogenous 1AA (Pilet et al., 1979). Use of growth-regulating chemicals on prolific and non-prolific maize plants were found by Sorrells et al. (1978) effect maize ear development. They used the compound N-1-napthylphthalmic

acid (NPA) to inhibit auxin translocation. Since the use of NPA significanLLy increased the LoLal ylid (f non-prol ific cuLivars and increased the lower ear grain weight and ear number of all their cultivars, they suggested that 1AA may interact with other hormones in a time-dependent mode for inhibition of lower ear development.

Various cations have been found to alter the auxin activity of 1AA. Evans et al. (1980) reported that when 1AA was present at concentrations that caused inhibition to the elongation of maize roots, the pH of the bathing medium increased sooner than that during a latent period for such inhibition of elongation. They concluded that the cell-wall pH was modified by the lAA and played a role in the control of root elongation. Under san Lnv cond it i ons, Pandey (L.970) notvd t hat , when miia I z' ds were treated with 0 to 900 ppm in salt solutions of 1000, 2000, and 3000 pmhos/cm, there was a change in amino acid content. As salt concentration was increased, the level of aspartic acid and glutamine decreased. Presence of added lAA to the seeds resulted in an increase of tyrosine, tryptophan plus valine, alanine, cystine, and arginine in the maize plants. Goring et al. (1979) reported that 1AA application and temporarily-reduced






38


water potential reacted on the transmembrane potential of maize coleoptile within 15 minutes. This could be explained by lAA and water stress inducing activation of f+ secretion by the plasmalemma. Work by Nowakowski (1979) also showed that when maize was grown under conditions of osmotic stress, 1AA oxidase activity was reduced in the roots and shoots. Todor et al. (1977) observed that,-when Mg deficiency was induced in maize, addition of Mg alone or with lAA increased biomass accumulation and changed the plant chemical composition. Manganese restored the growthpromoting effect of lAA and decreased malate dehydrogenase activity of maize in an experiment performed by Kobyl'skaya et al. (1976). Phosphorus nutrition of maize was affected by a positive interaction between y-radiation and the addition of lAA, Zn, or Mn separately or together (Trifu and' Osvath, 1978). With oat (Avena sativa L.) coleoptiles, Rubenstein et al. (1979) demonstrated that addition of Cd in the bathing medium stimulated iAA activity because protons were released from the cell-wall. Maize coleoptile segments under anaerobic conditions showed inhibition of cell enlargement, H+ extrusion, and K+ uptake which was attributed to imbalance of lAA activity (Rasi-Caldogno et al., 1978). In another study, Nelles (1977) reported that maize coleoptiles treated for 16 hours with 10 5M 1AA increased in K permeability and decreased in Na permeability. Haschke and Luttge (1978) found that Avena coleoptile segments treated with 1AA exhibited H+ release by K+ exchange with a concomitant synthesis of malic acid.





39


Enzymatic synthesis of IAA from tryptophan was found to be decreased when maize plants were Zn-deficient and was restored rapidly after Zn application (Karakis, 1974).

The binding of auxins to receptor sites of maize tissue

was modified by a naturally-occurring compound 6, 7, dimothoxyl-2benzoxazoline (OMBOA) in a study by Venis and Watson (1978). Other factors affecting the primary root requirement of maize for IAA were reported to be the lAA gradient from shoot to root (Martin et al, 1978), inhibition of IAA activity by red light (Vanderhoef and Briggs, 1978), and polar transport of 1AA in vascular tissue of maize (Wangermann and Withers, 1978). Studies by Patel et al. (1978) were conducted using 2-day-old maize seedlings cultured in 10~4 ppm of 1AA for 24 hours. They reported that the riboxynucleic acid content was increased in elongating cells by the 1AA treatment at different phases of elongation. Hall and Bandurski (1978) used 14C-lAA, 3H-lAA, or 3H-tryptophan to trace 1AA movement from endosperm of maize to the shoot. Their results showed that 1AA can move from endosperm to the shoot at a rate equivalent to that for simple diffusion. However, about 98% of the transported IAA was converted to other compounds during the transport. They concluded that the rate of 1AA and tryptophan-derived 1AA transport of lAA and active 1AA absorption by maize coleoptiles were both found to be temperature dependent and the 1AA absorption of 14C-lAA from apically applied donor blocks was a linear function of time in experiments by Naqvi and Gordon (1978). To assist determination of lAA, improvement in






40


assay procedures for 1AA were developed by Mousdale et al. (1980).

Schurzmann and Hild (1980) found that externally applied lAA and abscisic acid (ABA) on vertical maize roots caused root curvature toward the donor agar block having the 1AA. When the roots were horizontal, lAA applied on the upper side inhibited or delayed normal geotropic downward bending. The extent of retardation and inhibition of curvature depended on the lAA concentration in the donor block. Growth or curvature of roots was not affected by ABA in similar experiments. When root tips or coleoptile tips were placed on vertical roots, root curvature was observed.

Lee (1980) sequentially treated stem segments of maize with phenolic substances and 2- 14C-lAA. The results suggested that the phenolics also affected the enzymatic oxidation of 1AA in vivo in the same way as in vitro. Phenolic pretreatment that affected formation of bound 1AA was found to be ferulic acid, coumaric acid, or 4-methylumbelliferone. Compounds which were cofactors of 1AA-oxidase increased the lAA incorporation while inhibitors of lAA-oxidase decreased it.

Root segments of maize taken 2 mm long at 1 cm behind the

root apex showed stimulation of elongation at pH 4. lAA decreased elongation at pH 4 but stimulated it at pH 7 after a lag phase (Edwards and Scott, 1974).

In another study by Jacobs and Ray (1976), it was found that auxin induced a decrease in the free space pH within 12 minutes for maize and 30 minutes for pea. There was a corresponding cell elongation at these times. Auxin analogs p-chlorophenoxyisobutyric





41


and phenylacetic acid did not stimulate elongation or a decrease in pH in the tissue free space. These findings are consistent with the acid secretion theory of auxin action.



Classification

Although Eucalyptus forests almost everywhere in Australia look alike, there are about 500 species, subspecies or varieties within the genus (Chippendale, 1973).

The only textbook which deas comprehensively with eucalyptus is that by W. F. Blakely, A Key to the Eucalypts,, which was first published in 1934 and later reprinted with some additions by R. D. Johnston in 1955 and with a nomenclature appendix by R. D. Johnston and Rosemary Marryatt in 1965. In the third edition of 1965, 676 species, sub-species, varieties and hybrids are recorded. Excluding the hybrids and doubtful species, and allowing for synonymy resulting from recent investigations, there are 444 separate valid taxa for which descriptions have been published (Chippendale, 1973).

Pryor and Johnson (1971) drew up a classification incorporating the results of more recent study, drawing particularly upon information from the associated disciplines of genetics, ecology, and anatomy, as well as amplifying the study of morphology along traditional lines. In this classification, the genus Eucalyptus is divided into seven subgenera. In turn the subgenera are divided into sections, series, subseries, superspecies, species, an1d sub'pc es.





42


Eucalyptus grandis Hill ex Maiden belongs to the subgenus Symphyomyrtus and the section Transversaria (Pryor and Johnson, 1971).

Eucalypts can be either trees or shrubs (Chippendale, 1973). The tallest species is mountain ash (E. regnams) from Victoria and Tasmania, recorded to about 98 m. In Western Australia, the tallest species is the karri (E. diversicolor) growing to about 76 m. On the other hand, some eucalypt species have a maximum height of 4.5 to 6 m, while some are shrubs only about

2 m high.

E. grandis is a tall straight tree up to 46 m high. The

bark is smooth and deciduous, white or subglaucos (Blakely, 1955). Its timber is red, light and durable. The juvenile leaves are opposite for 3 to 4 pairs, shortly petiolate, oblong-lanceolate, thin, undulate, 3 to 6 by 1 to 2.5 cm. The intermediate leaves are alternate, petiolate, broadly lanceolate, slightly undulate, 12 to 18 by 5 to 6 cm. Mature leaves are alternate, petiolate, narrow-lanceolate, acuminate, undulate, 13 to 20 by 2 to 3.5 cm. Venation is moderately fine. Umbels are axillary, 3-to-10-flowered, or more. Peduncles are compressed, 10 to 12 mm long. Buds are pyriform, usually contracted in the middle, pedicellate, glaucous, 10x5 mm. Operculum is conical to shortly rostrate, shorter than the calyx-tube. The name Eucalyptus refers to the operculum, being derived from the Greek eu = well, and kalyptos ~ covered.










The Eucalypts Range of Growing Conditions

Eucalyptus is by far the most important genus of Australian forest trees. Its members dominate 95% of the Australian forest area and spread out over much of the remainder of the country (Hall et al., 1970). A wide variety of hardwood timber is produced from these species; timbers which display a considerable range in characteristics such as color, weight, hardness, toughness, strength, elasticity, durability and fissibility. Because of this diversity of properties, eucalypt timbers have innumerable uses, many being pre-eminent for heavy structural purposes such as bridge building and harbor works.

Apart from the major uses as timber and its derivatives,

these trees yield valuable essential oils by foliage distillation, oils that are widely used in pharmacy, perfume manufacture, and industry (Hall et al., 1970). Tannins are extracted in commercial quantities from the wood and bark of some species.

Exceptionally hardy species such as some of the snow gums can withstand exposure to high winds, intense cold and heavy snowfalls above 5,000 to 6,000 feet in the Australian Alps and 3,000 feet in the highlands of Tasmania. At the other extreme, in the hot, parched desert and semi-desert regions of the inland, the eucalypts are restricted to watercourses and sheltered depressional areas where sufficient moisture is available to maintain existence during the normally long droughts. Many species exist on less than 250 mm of rain a year (Hall et al., 1970).




41,


Eucalypts have been able to adapt themselves to a wide range of conditions in both tropical summer rainfall and cool temperate winter-rainfall areas. They occupy both dry and wet sites, even

swamps in places, exposed positions and sheltered congenial slopes and valleys, infertile sands, richer mellow loams and intractable clays (Hall et al., 1970).

Most eucalypt species produce seed prolifically so that, if soil conditions are favorable for germination, an abundant crop of young seedlings is assured to restock whatever blank spaces there may be (Rule, 1967). Apart from these deaths due to overcrowding, bushfires, grazing animals, insects, and fungi take heavy toll of such regrowth right from the start, unless man comes to nature's aid.

One reason why eucalypts have become so popular, for

afforestation in other countries where the climate approximates to that of their native habitat, is that they are easy to raise from seed in forest nurseries. Australia relies largely on natural regeneration (seeding from parent trees) wherever possible. Eucalypts as an Exotic Plant

The story of the cultivation of the eucalypts and the early recognition of their economic possibilities commenced with the establishment of small plantation in southern Europe and North

Africa about ]O0 years ago (Penfold and Will Iti, 1961). Since then, the case with which the eucalypts can be cultivaLed, their rapid growth, and their adaptability, have led to their widespread











introduction into many countries, especially in those which are poorly endowed with forest resources.

Eucalyptus was introduced into California in 1853

(Penfold and Willis, 1961). Later seeds of many species were raised and distributed from 1886 to 1888. Plantations were soon after established in certain areas of California, Arizona, New Mexico, and Florida.

Eucalypt plantations were established in Kenya at the beginning of the twentieth century. Eucalyptus grandis

E. grandis comes from eastern Australia (FAO Forestry

Development Paper, No. 19, 1974). It comes from areas with a rainfall of 900 to 1,270 mm, fairly well distributed throughout the year, but with a marked summer maximum, especially toward the north of its range.

The timber of E. grandis is lighter, softer and more fissile

than that of most eucalyptus, with moderate strength and durability, prone to warping and other defects especially when sown from young or fast-grown trees (Streets, 1962). The timber quality of fast-grown hybrids between E. saligna and E. grandis would seem to need examination. Both species and the hybrid make good poles but need preservative treatment for telegraph and transmission poles.

Only small areas of authentic E. saligna and E. grandis of Australian origin have been planted in savanna conditions (FAO Forestry Development Paper, No. 19, 1974). In trials in Zambia,





46


it was found that E. saligna was more drought sensitive than E. grandis or E. "grandis" from Africa. (The latter is of mixed origin and the name denotes the common form grown from African seed).

Site Quality

As regards sites, much of the most successful planting of

E. "grandis" in Kenya and Malawi has been done at high altitudes outside the savanna region, and in other countries in conditions of rainfall and moisture corresponding to moist high forest types. Phenomenal rates of production have been achieved under such favorable conditions. In Zimbabwe, formerly called Rhodesia, mean annual increments of 61 to 66 m3/ha have been recorded on the best soils in high rainfall areas (Barrett and Mullin, 1968). This is, however, exceptional. The tree requires good, deep permeable soils and cannot stand poor drainage or water-logging. At the same time, it cannot tolerate drought. A rainfall of 900 mm and upward, with a not too severe dry season, is suitable. In Zambia, where it is the major plantation species, it grows very well on the northern Plateau at elevations of 1,220 m, where it achieves a mean annual top-height increment of 5.1 m and a mean annual diameter increment of 4.2 cm in 2 to 4 years.

E. "grandis" was tried in Congo under a rainfall of 1,200 to 1,300 mm, but with a 4-month dry season. Though it started well, after the first 3 years, its condition deteriorated and this was attributed to shortage of water (Groulez, 1967).





4 /


E. "grandis" in its various forms sets seed at an early age. It is relatively easy to handle in the nursery. Seed is sown direct into pots at the rate of 1 g/100 pots. Height growth is rapid and most seedlings reach a height of 30 cm in 10 weeks. In Zambia, smaller plants not more than 23 cm high are preferred. As for all eucalyptus planting, clean site preparation is desirable, and indeed is essential where moisture is likely to be insufficient at any time of the year. Clean weeding is necessary until the canopy has closed enough to suppress grass and invading weeds. The species is susceptible to termite attack and the usual precautions of applying insecticides at the time of planting have to be taken, especially on the drier sites where termite damage is always more severe. It also suffers from die-back on B-deficient soils and, in such cases, application of borate fertilizer may be necessary.

Fertilizers

There is very little information concerning the effect of fertilizers on the growth of eucalypts. From the scattered, rather empirical data that have been collected, it appears that tests with phosphatic fertilizers show little or no effect while -nitrogenous fertilizers result, in some cases at least, in quite striking responses (Penfold and Willis, 1961).

Using pot experiments with several species, Beadle (1953)

found that added N and phosphate caused increased growth and the production of larger, softer leaves. This indicates that the addition of nitrogenous and phosphatic fertilizers to plantations






48


established for the production of leaf products, such as essential oils, may increase the overall yield by increasing the amount of leaf material produced per hectare. Container-Grown Seedlings

Container seedlings and greenhouse production are no longer new concepts in many countries throughout the world. However, major research and development commitments and large investments in production facilities for mass production of container-grown seedlings were made only in the last decade in North America (Stein et al., 1975). The use of container-grown stock varies among regions, because the relative advantage of this more labor-intensive system over the production of bare-root seedlings depends on shock tolerance of the species used, on climate, soil conditions, and on planting methods (Pritchett, 1979).

The reasons or objectives for using container-grown

seedlings vary among organizations, but they generally fit into one or more of the following broad categories (Stein et al., 1975).

"1. Meet accelerated demands for nursery stock. Facilities

for producLtion of seedlings In containers can be expanded

rapidly and seedlings can be produced quickly on more

certain, flexible schedules than in bare-root nurseries.

2. Produce some species more readily. For a variety of

reasons, certain species are difficult to produce in bare-root nurseries or are particularly sensitive to

bare-root handling.






49


3. Achieve greater production and planting efficiencies.

Through use of container-grown seedlings, improvements appear possible in most phases of reforestation. This includes more efficient use and control of genetically

improved seed, production of more uniform stock,

better protection of seedlings, greater opportunities

for mechanization, improved quality and speed of planting,

and easier planting among residues or stock.

4. Extend planting seasons. Greater flexibility in production

of seedlings and the protection that is provided by the

container may permit planting at times when bare-root

stock is not available or not properly conditioned.

Lengthening the planting season may also permit use of

a smaller, or more stable work force.

5. Improve survival and growth of out-planted seedlings.

Achieving better survival and growth is a universal

goal for everyone who tries new reforestation techniques." Types of containers

Several types and sizes of containers are commonly used. These may be grouped into three categories: tubes, blocks, and plugs. Tubes can be constructed of either biodegradable or non-degradable plastics, or of kraft or other paper. Tubes require filling with a soil mixture or other growth medium. Some control in the degradation rate of the material from which the tubes are constructed is important to the health of the seedling and for handling purposes (Pritchett, 1979).




30


Blocks are similar in shape and size to tubes, but they have

no outer wall and require no filling. The block is both the container and the planting medium, and seeds are sown directly in the block. The entire package is later transplanted into the soil. They are molded from bonded softwood pulp, polyurethane foam, peat, peatvermiculite mixtures, or similar materials in which nutrients may be incorporated. Blocks have given excellent results under many conditions, but, unless produced locally, freight cost can be prohibitive (Pritchett, 1979).

Plugs consist of seedlings grown in soil-filled molds, but,

unlike tube- or block-grown seedlings, they must be removed from their containers before outplanting. Since the growth medium is bound only by the seedling roots, the plug can be rather fragile and not easily planted by machines.











MATERIAL AND METHODS

Soil Properties

The main coffee-producing areas of Kenya of which Ruiru and Kabete are representative, are located on closely similar soil types, named by Gethin Jones (1949) as the Kikuyu series. These soils are deep, porous and naturally well drained. They are latosols and are dived from a volcanic parent material, tertiary trachytic lava, by weathering in situ. They have a high pore space, a fairly high cation exchange capacity and a high clay content, yet the field texture is that of a friable loam (Pereira, 1957). The highly porous surface of the Kabete soil

has a good natural crumb structure and It is resistant to erosion. The soil depth may exceed 20 feet on the main ridges and can fall to 2 or less feet on the flanks immediately above the river valleys (Gethin Jones, 1949).

The black cotton soils are also derived from volcanic parent materials of the Tertiary period. The Mwea soil was sampled at

the Mwea Plain and the Athi soil was sampled at the Athi Plain. These soils have developed wherever the drainage system was poor.

Kabete soil is dominated by kaolinite and halloysite but Mwea and Athi soils are dominated by montmorillonite which subjects then to extensive swelling and waterlogging during wct seasons and dry ing and ernekrg (iing dry ne;mnoons. Other Ho) I propX ric i ar-C slmow1i In a table.


5.1





52


Soil Preparation

One hundred kilograms of each soil sampled at two depths, 0- to 15-cm and 15- to 30-cm, were sent from Kenya. They were air-dired and ground to pass through a 10 mm sieve. Thirty nine 1000-g samples of each soil were weighed into polyethylene bags and placed in plastic pots. A greenhouse experiment was conducted to determine the growth and composition of E. grandis when treated with 1AA and three CSP sources at three rates. The CSP sources were: (i) reagent grade monobasic calcium phosphate powder,

(ii) pelletized CSP, and (iii) pelletized CSP containing 100 ppm of lAA. The latter two CSP sources were supplied by the International Fertilizer Development Center (IFDC), Muscel Shoals, Alabama. The supplier stated that the analyses of the materials indicated that the two materials were essentially the same in P205 content. Both sources contained 15.7% water-soluble P, while source (ii) contained 19.4% citrate-soluble P, and source (iii) contained 19.9% citrate-soluble P. The CSP was applied to give 28, 56, and 112 kg P/ha and the IAA without CSP was applied to give 0.031, 0.062 and 0.124 kg 1AA/ha, these IAA concentrations were equivalent to those supplied by the rates of pelletized CSP with 1AA. The CSP treatments were added to the soils in the bags and mixed thoroughly. When 1AA was used alone, 1000 mg were dissolved in alcohol in a liter flask and made to volume with distilled water to give 1000 ppm 1AA. From this, a secondary dilution was prepared and used to give 0.031, 0.062 and 0.124 kg 1AA/ha in triplicate pots of soil. Each such




53


treatment was thoroughly mixed with the soil after each appropriate quantity of lAA was added from a dispenser. The soil in each pot was watered to about 75% of its water-holding capacity. The experiment was a completely randomized design.

Eucalyptus Experiment

After the moist soils had equilibrated with the fertilizer

treatments for 4 days, six pelletized E. grandis seeds were planted in six holes (one in each hole) at about 10 mm depth in each pot and gently covered with loose soil. About 3 weeks after emergence, the seedlings were thinned to three plants in each pot. At 5 weeks after emergence, NH4NO3 was added to give 224 kg N/ha. Potassium and zinc sulfates were added at 10 weeks after emergence to give 224 kg K/ha and 44.8 kg Zn/ha. When the plants were about 3 months old, magnesium nitrate was added to give 112 kg Mg/ha. Due to rapid evaporation of water in the greenhouse, it was necessary to flood the pots regularly in order to maintain suitable moisture content for the plants. In the beginning of spring, the temperatures were usually from 27C to 32'C during the day but were higher towards the end of the season, occasionally reaching about 46C.

Height measurement of each plant was taken at 2, 3, and 4 months. At the end of 4 months, the plant tops were harvested and stem thickness at the base was measured with a micrometer. The plants were air-dried for a few days and then transferred to a drying room at 60*C. After drying was completed, they were





54


weighed and milled. Small quantities of leaves of eucalyptus from the top layers of Mwea and Kabete soils were ground separately.

After the eucalyptus harvest, soil samples were taken from the pots, air-dried, and ground in preparation for analysis.

Maize Experiment after Eucalyptus

Maize cultivar 'Pioneer 3160' was planted in the soils after eucalyptus harvest without disturbing the soil. Five seeds were planted in each pot. Because the temperature in the greenhouse was almost always 30C during the day, the soils in the pots were flooded periodically to ensure optimum moisture content for the plants. About a week after emergence, they were thinned to three plants per pot.

Three weeks after emergence, NH4NO3 was added to give 224 kg N/ha and at 4 weeks after emergence (NH4)2SO4 was applied to give 224 kg N/ha.

Height measurements were taken at 2, 4, and 6 weeks after emergence. The plants were harvested 6 weeks after emergence, air-dried for 2 days and then transferred to a drying room. After they were completely dry, they were weighed and ground.

After the maize harvest, soil samples were taken from the pots, air-dried, and then ground in preparation for analysis.

Maize Experiment with Two Soils

Athi and Kabete soils from 0- to 15-cm depths, with fresh CSP and 1AA treatments at the same rates as had been used for eucalyptus, were planted with the same above variety of maize









in a separate experiment in the greenhouse. Watering and the temperatures were the same as for the succession experiment. These plants received the same amounts of NH4NO3 and (NH4)2SO4 as those in the succession experiment at the same time. Height measurements were taken at 2, 4, and 6 weeks after emergence and were harvested after the last height measurement. A single

fourth leaf from each pot was put in a separate bag. These were all air-dried for 2 days and then transferred to a drying room. After they were completely dry, they were weighed and ground. The leaf samples which had been put in separate bags were also ground separately. Weights of these latter samples were included with the main weight of the harvested tops.

After the maize harvest, soil samples were taken from the

pots, air-dried, and then ground in preparat ion for analysis. The maize roots were separated from the soils and washed free of soil before drying at about 70C in an oven for several days. When dry, the roots were weighed and then ground with a small mill.

Analytical Methods

Particle-size analyses on soil samples less than 2 mm were done according to the pipet method as outlined in the Soil Survey Investigations Report No. 1 (1972).

Organic carbon in the soils was determined according to

the method of Walkley (1946). Walkley and Black (1934) obtained

60 to 86% recovery of C, for which their multiplying factor was






56


1.30. Peech et al. (1947) reported a similar multiplying factor of 1.33. In view of their report, a multiplying factor of 1.33 was used in the present study.

Nitrogen in eucalyptus leaves from the top samples

(0 to 15 cm) of Mwea and Kabete soils was determined according to the semimicro-Kjeldahl method as outlined in Black (1965).

Soil pH was determined by glass electrode pH meter using a 1:2.5 soil to water ratio, following the procedure outlined by Black (1965).

Reagents for P Determination

Double Acid (DA) reagent. The DA reagent is 0.05 N

hydrochloric acid in 0.025 N sulfuric acid. This reagent was prepared by pouring about 15 liters of deionized water into a 20-liter bottle and adding 14 ml of concentrated sulfuric acid and 83 ml of concentrated hydrochloric acid. The volume was made to 20 liters and thoroughly mixed.

Reagent A. Weigh 12 g ammonium molybdate and dissolve

in about 400 ml of distilled water. Add 0.2908 g of antimony potassium tartrate and dissolve in 100 ml of distilled water. Both of these dissolved reagents are added to 1000 ml of 5 N H2SO4 (148 ml concentrated H2SO4 per liter), mixed thoroughly and made to 2 liters. Reagent A was stored in pyrex glass bottle in a dark and cool compartment.

Reagent B. Dissolve 1.056 g of ascorbic acid in 200 ml of reagent A and mix. This reagent was prepared as required, as it does not keep for more than 24 hours (Murphy and Riley, 1962).





57


Sodium bicarbonate (SB) reagent. This reagent is 0.5 M

NaHCO3 solution at pH 8.5. The pH of 0.5 M NaHCO3 was adjusted with 5 M NaOH for 10 liters of the solution which was prepared. The solution was stored in a polyethylene container.

Carbon black. Darco activated charcoal was used.

P standards. Exactly 0.2195 g of oven-dry KH2PO4 was

dissolved in 500 ml of distilled water and 5 ml of concentrated sulfuric acid were added as a preservative and diluted to 1000 ml in a volumetric flask. This standard was 50 ppm P and was used as needed. A secondary P standard was prepared by pipetting 25 ml of the primary P standard into a 250-ml volumetric flask and was made to volume with DA reagent. This standard contained

5 ppm P and was kept in a refrigerator. Soil Extraction

In order to use an appropriate DA/soil ratio in the

extraction, pH of blank (DA reagent only) was compared with pH of various solution/soil ratios. The solution/soil ratios examined were 10:1, 7:1, and 4:1 employing 50, 35, or 20 ml of DA reagent/5 g soil respectively. The pH of the supernatant after shaking for 30 minutes was measured. The pH of the 10:1 ratio was the closest to that of the reagent.

A 5.0-g sample of each soil sample was weighed into 125-ml extracting bottles and 50 ml of DA reagent were added with an automatic pipette. The bottles were placed in a rack on a mechanical, reciprocating shaker and shaken for 30 minutes.






58


Sartain et al. (1976), working with ten mineral and organic soils from Florida, obtained a curvilinear increase in the quantity of P extracted by DA reagent and 0.03 N NH4F in 0.05 N HCU with a maximum occurring between 15 and 20 minutes. A longer extracting (shaking) time was chosen for the present study because the soils had a higher clay content. The soils were filtered through Whatman No. 2 filter paper. The filtered extracted solutions were used for elemental analysis.

The 0.5 M NaHCO3 method of Olsen et al. (1954) was used with a slight modification. A 2.5-g portion of soil was shaken with 50 ml of the solution for 30 minutes. Activated charcoal (Darco) to remove dissolved organic matter was added and the extract shaken vigorously before filtering through Whatman No. 2 paper. These filtrates were clear. Extraction of Plant Tissue

Eucalyptus. A 0.50-g sample of ground eucalyptus tops

(or leaves) was weighed into crucibles and heated in a muffle furnace for 2 hours at 350*C. Heating was continued at 550*C for 4 hours. The crucibles were allowed to cool. A few drops of distilled water were added to moisten the ash and 5 ml of 40% HCl (2 parts concentrated HCl to 3 parts distilled water) were added and the solution was gently evaporated to dryness on a hot plate in a fume cupboard. The crucibles were washed with 50 ml of N HCl (a little at a time), filtering the washings through Whatman No. 2 paper. The filtrate was collected in bottles and used for elemental analysis.






59


Maize. A 0.50-g sample of dry maize tops was weighed and

heated in a muffle furnace at 350*C for 2 hours. The temperature was raised to 550%C and heating continued for 4 hours. After cooling, the ashed samples were moistened and 5 ml of 40% HC were added and evaporated to dryness on a hot plate. Due to the presence of black ash, these samples were reheated in the muffle furnace at 350'C for an hour and then at 550*C for 4 hours. After cooling, the ash was moistened with a few drops of distilled water and 5 ml of concentrated HNO3 were added and evaporated to dryness on hot plates. These residues were washed with 50 ml of N HCl, collecting the filtrate through Whatman No. 2 paper and retained in polyethylene bottles.

A 0.05-g sample of the fourth maize leaves from Athi and Kabete soils (0- to 15-cm depths) were weighed and ashed as the maized tops had been done. A 0.50-g sample of maize roots from these same soils were ashed as above and the ash dissolved in 50 ml of 1 N HCl.

P Determination

Zero, 1, 2, 3, 4, and 5 ml of the 5 ppm P standard were pipetted into 50-ml volumetric flasks. They were filled half-way with distilled water. A few drops of 2,4-dinitrophenol were added followed by 2 N NaOH until a yellow color appeared and N HC was added drop by drop until the yellow color just disappeared. Then 8 ml of reagent B were added from an automatic dispenser, made to volume with distilled water, and





60


mlxed well. The coLor was allowed to develop for 20 minutes before being read on a Bausch & Lomb Spectronic 21 at 882 unm. The P concentrations in the standards were 0, 0.10, 0.20, 0.30,

0.40 and 0.50 ppm. The zero P standard was used to set the instrument.reading at 0.000 P concentration and 0.50 ppm P standard was used to set the maximum reading 0.500. Suitable aliquots of the soil extracts were taken.

A 1-ml aliquot of the plant extracts was taken for P

analysis. Color was developed in the same way as for the standards using the same instrument at 882 nm and the calibrated readings were taken from the instrument.

Calcium, Mg, Cu, Fe, Mn and Zn were determined by atomic

absorption spectrophotometry using a Perkin Elmer 5100 instrument and K was determined by emission flame photometry at 769 nm. Statistical Analysis

All the experiments were completely randomized designs. The computer used for the statistical analysis is an Amdahl V-6-II and IBM 3033 with an OS/MVS Release 3.8 and J 2S2/NJE Release 3.

The analysis was done using an in-house program at the

Department of Statistics, University of Florida. The analysis was obtained by converting the factors 1AA rate, P source, and P rate to a single factor labeled as treatment, with 13 levels. Single degree of freedom comparisons were then defined based on the original 3 factors. The contrast used and the corresponding treatment are given in the following table.






61


Treatment comparison

Linear effect, 1AA alone Quadratic effect, 1AA alone CSP Powder vs CSP Pellet (Form) Linear effect, CSP alone (Rate,Linear) Quadratic effect, CSP alone (Rate, quadratic) Component Form x Rate interaction Component Form x Rate interaction Linear effect, lAA+CSP pellet Quadratic effect, 1AA+CSP pellet 1AA alone vs CSP alone 1AA+CSP pellet vs IAA alone, CSP alone Control (No lAA, No CSP) vs others


Abbreviation


1
2
3
4
5
6
7
8
9 10 11
12


1AA,L IAA,Q CSP form
CSP,L CSP,Q
Form x rate,L Form x rate,Q CSP-lAA,L CSP-lAA,Q IAA vs CSP alone CSP-lAA vs CSP+1AA Control vs others


In subsequent tables, the rates were given as r2, r3,.... r7, which stand for the rates of IAA and CSP which were applied, in kg/ha. Thus, for IAA, terms r2, r3, and r4 represent 0-031, 0-062, and 0-124 kg 1AA/ha, respectively. For CSP, r5, r6, and r7 represent 28, 56, and 112 kg P/ha, respectively.

The abbreviations lAA, CSP, DA, and SB are used to represent indole acetic acid, concentrated superphosphate, double acid, and sodium bicarbonate, respectively. Phosphorus extracted by


DA and SB is termed DA-P and SB-P, respectively.













RESULTS AND DISCUSSION

Eucalyptus Experiment

Soils

Although the soils used in the studies were very similar in pH, Kabete soil had a much higher organic matter content than Athi or Mwea. On the other hand, Mwea soil had a much greater P extractable by double acid (DA-P), being 550 ppm, than either Athi or Kabete each of which had less than 10 ppm P (Table 1). Athi and Mwea soils have more than 50% clay which is mainly montmorillonite. This property made them difficult to water suitably because of the ease of swelling when wet which inhibits water infiltration. Both depths of the Kabete soil have an average of 50% silt and an average of 17% sand. This property, besides its kaolinitic nature, facilitated watering and aeration. Moreover the high percentage of organic matter particularly in the 0- to 15-cm layer of Kabete soil enhanced good crumb structure, a desirable characteristic. Growth Factors

During the early growth of eucalypt seedlings, there was

widespread occurrence of purplish colors on the stems on most plants except those growing on Mwea soil which was very high in P as determined by double acid. The purple (or brown) color was believed to be due to P deficiency. In the later stages of growth (that is about 2 to 3 months), the lower leaves started to lose the green color, becoming yellow and finally red. Addition of magnesium nitrate apparently rectified this problem.


62






63


Table 1. Some properties of soils from Kenya.


Soil
Athi,cm Mwea,cm Kabete,cm
Analysis 0-15 15-30 0-15 15-30 0-15 15-30



pH 6.5 6.8 6.3 6.3 6.4 6.4
(1:2-5,
soil to water)
%C 1.76 1.65 1.69 1.58 7.09 3.34
% sand 12.1 11.6 7.6 7.6 19.7 14.7
% silt 32.4 30.5 25.6 24.4 45.0 55.1
% clay 55.5 58.0 66.8 68.0 35.4 30.2
ppm )P 4.5 5.5 550 550 7.0 1.0
by DA
method






64


Significant responses to treatments, soils, soil depths, and

their interaction with treatment comparisons were obtained (Table 2). At 2 months since emergence, height showed a significant response to CSP form, the means being 18-8 and 16-9 cm, for the powder and pellet forms, respectively (Table 3). This significant difference is substantial on the Kabete soil for which the height for the three rates of CSP powder are approximately double those of the corresponding rates of CSP pellet. There was a linear response of height to CSP form and a quadratic response to P form and rate at

2 months since emergence (Table 2). The height was less where lAA alone was used compared to that for CSP alone but this effect differed between soils and depths. Growth increase for CSP was 15-9, 7-6, and 6-3 cm for Athi, Mwea, and Kabete soils respectively (Table 4). Depth of soil also influenced the height differences between 1AA and CSP treatments, Table 5, and the difference in height was 8-8 cm for plants on soil from 0 to 15-cm depth compared to an ll-2-cm difference at the 15 to 30-cm depth.

A comparison of CSP+1AA and CSP with lAA (i.e. CSP-lAA) shows that the height was significantly less for CSP+1AA for Athi and Mwea soils (Table 6). Depth influenced this difference in that the height difference was greater for the 15 to 30-cm depth (5-9 cm) than for the 0 to 15-cm depth (3-3 cm), Table 7. Growth on control treatments was less than on the other treatments (comparison 12) and these differences were influenced by both soils and soil depths, Tables 8 and 9. For Athi and Mwea soils, the height was significantly greater for the other treatments than for the control. However, the






65


Table 2. Means and significant height
grown on three soils treated


responses for Eucalyptus grandis with 1AA and CSP.


Height, months Treatment comparisons
Factor Rate 2 3 4 No. Type Height months
2 3 4


kg/ha
Treatment
Control
1AA r2
1AA r3
IAA r4
CSP powder r5 CSP powder r6
CSP powder r7 CSP pellet r5 CSP pellet r6 CSP pellet r7 CSP-lAA r2+r5 CSP'lAA r3+r6 CSP'lAA r4+r7


Soils
Athi Mwea Kabete


cm


12.4 8.3 7.7 7.6 16.5
20.0
19.8 16.5 15.9 18.3 17.7 17.1 17.1


15.9 18.7 10.3


25.5 20.7
21.0 21.2 32.1 35.0 33.5 31.1 30.8 33.1 33.0 31.1 32.9


26.9 32.8 28.3


sum of squares
** ** **


51.7 53.2
49.7 50.5 58.1 62.2 59.9 60.1 62.3 61.8 63.2 57.3 61.0


52.2
60.4 60.8


1
2
3
4
5
6
7
8
9 10 11
12


1AA,L 1AA,Q CSP form CSP,L CSP,Q
Form x rate,L Form x rate,Q CSP'lAA,L CSP-lAA,Q 1AA vs CSP CSPdlAA vs CS Control vs ot


**
?+lAA** hers **


** ** **


Soils x treatments


**
**


**


**
**
**


**

*


as above


**


**


1
2
3
4
5
6
7
8
9 10 11
12


** **



**


**
**
**


**
**
**


**
**
**





66


Table 2-continued.


Height, months Treatment comparisons
Factor Rate 2 3 4 No. Type Height, months
2 3 4

kg/ha cm sum of squares
Depths
Depths x treatments as above ** ** **
1
2
3
4
5
6
7 **
8
9
10 ** **
11 ** **
12 *

* **
and denote significance at the 0.05 and 0.01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).






67


Table 3. Soil x treatment means for CSP forms x rate quadratic effects
found for eucalypt height at 2 months. P P Soil
form rate Athi Mwea Kabete Mean


kg/ha Means*, cm

CSP powder

28 14.4 20.4 14.6 16.5

56 22.4 20.7 17.0 20.0

112 20.6 20.2 18.7 19.8

CSP pellet

28 22.1 19.7 7.9 16.2

56 19.5 20.2 7.9 15.9

112 23.1 21.1 10.7 18.3


*


Difference above for mean values.


2.3 is significant at the 0.05 level except





68


Table 4. Interaction of soils for lAA and
height at three times.


CSP comparison for eucalypt


Soils Significant
Treatment Athi Mwea Kabete difference


Mean (cm) 0.05 level

2 months 1.8

CSP alone 20.3 20.4 12.8

lAA alone 4.4 12.8 6.5

Difference 15.9 7.6 6.3

3 months 2.4

CSP alone 32.7 34.8 30.4
1AA alone 11.5 26.8 24.0

Difference 21.2 8.0 6.4

4 months 4.9

CSP alone 58.7 62.3 61.7

1AA alone 35.7 55.3 61.3

Difference 23.0 7.0 0.4


lAA alone is the mean of treatments 2, mean of treatments 5 through 10.


3, and 4 and CSP alone is the


40






69


Table 5. Mean effect of soil depths on eucalypt height in response to
lAA and CSP alone.


Soil depth, cm Significant
Treatment 0-15 15-30 difference


Mean, cm 2 months


CSP alone

lAA alone Difference


18.6 9.8 8.8


3 months


CSP alone

1AA alone Difference



CSP alone 1AA alone Difference


32.9

24.4 8.5


4 months


60.1 53.9 6.2


0.05 level

1.7


17.2 6.0


11.2


2.4


32.3 17.6


14.7


4.9


61.4 48.4 13.0


as in Table 4.






70


Table 6. Interaction of soils on comparison of mean eucalypt
CSP with lAA (CSP-lAA) and CSP+1AA.


height for


Source Soils Significant
mean Athi Mwea Kabete difference


Mean, cm


CSP lAA CSP+1AA


Difference



CSP'lAA CSP+lAA

Difference



CSP-1AA CSP+1AA


Difference


2 months

21.3


16.6


4.7


3 months

31.6


30.8 0.8


4 months

61.9


58.8 3.1


0.05 level


1.8


9.8 9.7 0.1


2.4


28.4 27.2


1.2


4.9


58.7

61.4


- 2.7


22.1 12.4 9.7


35.4 22.1 13.3


60.9 47.7 13.2






71






Table 7. Interaction of soil depths on comparison of mean eucalypt
height for CSP1lAA and CSP + lAA.


Source Soil depth, cm Significant
mean 0-15 15-30 difference


Mean, cm 0.05 level

2 months 1.8

CSP'lAA 17.5 17.5

CSP+lAA 14.2 11.6


Difference 3.3 5.9

3 months 3.4

CSP-lAA 31.1 33.4

CSP+1AA 28.7 25.0


Difference 2.4 8.4

4 months 6.9

CSP-lAA 59.6 60.9

CSP+laa 57.0 54.9


Difference 2.6 6.0






72


Table 8. Mean effect of soils on eucalypt height, comparing controls
with the other treatments.


Treatment


Other treatments Control Difference



Other treatments Control Difference



Other treatments Control Difference


Soils
Athi Mwea


Mean, cm 2 months

16.7 27.8

5.5 18.9


11.2 8.9

3 months

19.2 32.8

13.1 32.1


6.1 0.7

4 months

45.2 60.4

36.8 59.7


8.4 0.7


Kabete


Significant difference 0.05 level

1.8


10.2 12.6


- 2.4


2.4


28.0 31.1


- 3.1


8.5


52.6 58.7


- 6.1






73






Table 9. Mean effect of soil depth in eucalypt height on control compared
to other treatments.


Soil depth, cm Significant
Treatment 0-15 15-30 difference


Mean, cm

2 months


0.05 level

1.7


Other treatments Control Difference


Other treatments Control Difference


Other treatments Control


Difference


14.1 10.3 3.8


3.4


28.7

22.4


6.3


6.9


58.0

45.8 12.2


15.9

14.4 1.5


3 months


30.4 28.5


1.9


4 months


58.9 57.6 1.3






74


opposite effect was observed in the Kabete soil, in which height of the plants on the controls was significantly greater than for the other treatments. This is really unexpected and is probably due to some other cause such as a more favorable property of Kabete soil (a latosol) compared to the black cotton soils (vertisol), such as higher organic matter and good structure which facilitate water infiltration and aeration. Considering the depths, there was no significant difference in height response to either the control or the other treatments for the 0 to 15-cm depth but the height was significantly greater for the other treatments than for the control treatment in the 15 to 30-cm depth (Table 9).

At 3 months, the height was less where 1AA alone was used

compared to that for CSP alone. Growth increase for CSP was 21-2, 8-0, and 6-4 cm for Athi, Mwea, and Kabete soils respectively (Table 4). The differences were significant but alike those at

2 months as presented above. As for the previous month, depth of soil also influenced the height differences between 1AA and CSP treatments, Table 5, and the difference in height was 8-5 cm for plants on soil from 0 to 15-cm depth compared to 14-7-cm difference at the 15 to 30-cm depth. The height was significantly less for CSP+1AA treatment than for CSP-lAA for Athi soil but no significant differences between these treatments were found for the other soils (Table 6). The influence of depth on these treatments, CSP+1AA and CSP-lAA, is that height was significantly greater for CSP-lAA treatment for soil at the 15 to 30 cm depth (Table 7). The height






75


difference for the 0 to 15 cm depth was 2-4 (which is not significant) and, for the 15 to 30 cm depth, it was 8-4 cm. Growth on control treatment of the Athi soil was significantly less than on the other treatments but greater for Kabete soil, Table 8. The influence of the 15 to 30-cm depth on this was significant, Table 9, but the

0 to 15-cm depth had no significant effect on the controls compared to the other treatments.

At 4 months, there was no significant difference in height between 1AA alone and CSP alone on Kabete soil. In fact the difference that existed before narrowed after 2 months and disappeared at 4 months. However, the plants treated with CSP alone on the Athi and Mwea soils still had significantly greater height than those with lAA alone. These differences in height were 23 and 7 cm for Athi and Mwea soil respectively. Considering the whole growing period for this study, the height difference between the plants treated with CSP alone and those treated with 1AA alone increased with time while that on Kabete soil narrowed and disappeared at 4 months as already stated above. The CSP alone had a significantly more favorable effect on height at both soil depths than lAA alone, as was the case previously (Table 5). Like the previous month the height was significantly greater for CSP-lAA treatment than for CSP-lAA on the Athi soil (Table 6). But unlike in the previous months, depth had no significant difference in its influence on these treatments (Table 7). Growth on control treatment of the Athi soil was less than on the other






76


treatments, though not significantly different. There was no difference in height for this comparison on the Mwea soil (being only O'7 cm). There was also no significant difference between the control and the other treatments in their effect on height of the plants on Kabete soil (Table 8). However, as was noted above, the plants on the control treatment had greater height on this soil than those on other treatments. Wherever this occurred, the probable cause is depression in growth caused by lAA which somehow cancelled the expected favorable effect of CSP. The height response of the plants was significantly less for the control than for the other treatments for plants grown on the 15-30 cm depth. The 0-15 cm depth had no influence on these treatment comparisons.

As shown on Table 10, CSP had a significant linear effect

on tops P. However, this effect is not clearly presented by Table 11 in which a quadratic effect is suggested by the data for both CSP forms and each of the three soils. There was a significant response of tops P to the lower P rates (28 and 56 kg P/ha) for both CSP powder and CSP pellet (Table 11). At these rates response in tops P was significantly greater for the pellet than the powder form of CSP. Response in tops P was greatest in the Athi soil and least in the Mwea soil, although the latter was much higher than the other two in DA-P.

Stem diameter responded significantly to the form of CSP,

soils, depths, and interactions. In all the soils, CSP treatments





77


Control
1AA
1AA
1AA
CSP Dowder CSP Dowder CSP Dowder CSP Dellet CSP pellet CSP nellet CSP-IAA
CS- AA
CSP-lAA


Means and significant stem diameter, weight of tops, and tops P of Eucalyptus grandis grown on three soils treated with lAA and CSP.


Rate Stem Tops Tops Treatment comparisons
diam. weight P No. Type Diam. Weight Tops P


mm g


5.0
4.3 4.3 4.4 5.7 5.8 5.5 5.8
5.4 5.7 5.7 5.0 5.6



4.8 5.5 5.5


17.6 13.7 13.3
14.3 23.8
24.0 23.6 23.7
22.1 25.0 22.8 21.7
22.4



17.5 21.5 22.9


Sum of sqiares


0.072 0.088 0.087 0.081 0.098 0.136 0.187
0.114 0.159 0.189
0.1J2
0. 143 0.190



0.130 0.116 0.137


1
2
3
4
5
6
7
8
9

11 12


1AA,L
1AA,Q CSP form
CSP,L CSP,Q
Form x rate,L Form x rate,Q
CSP-1-AA,L CSP-1AA,Q .IAA vs CSI' CSP-1AA vs Ct Control vs otl


** ** **




**
**
**


* *
4 1AA** hers **


**
**
**


**

* *
* *


** ** **


Soil x treatments


Table 10.


Factor


kg/ha


r2 r3 r4
r5 r6 r7
r5 r6 r7 r2+r5 r3+r6
r4+r7


Athi Mwea Kabete


as above


** **


**


1
2
3
4
5
6
7
8
9 10
11
12


*


*


*


**
**
**


**


**
**
**





78


Table 10-continued.


Factor Rate Stem Tops Tops Treatment comparisons
diam. weight P No. Type Diam. Weight TopsP


kg/ha mm g % Sum of squares

Depths ** **
Depths x treatment as above ** **


2
3 *
4
5
6
7 * *
8
9 *
10 ** *
11 ** **
12


* **
and denote significance at the 0.05 and 0.01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).






79


Table 11. Interactions of soils with response of eucalypt tops
P to CSP rates.


P rate, kg/ha

Soils 28 56 112

Mean, %
CSP Powder

Athi 0.099 0.138 0.211

Mwea 0.087 0.127 0.152

Kabete 0.107 0.144 0.197

Mean 0.098 0.136 0.187

CSP pellet

Athi 0.104 0.184 0.214

Mwea 0.103 0.136 0.171

Kabete 0.135 0.158 0.184


Mean 0.114 0.159 0.190





80


caused significantly greater stem growth than the lAA treatment as shown in Table 12. The greatest difference in stem diameter between these two treatments was 2'6 mm for the plants on the Athi soil although there was no significant difference in stem diameter among the soils treated with CSP. Stem diameter was significantly greater in the CSP-treated soils for the 15- to 30-cm depth than in the same depth of soils treated with 1AA (Table 13). There was no significant interaction for the 0- to 15-cm depth. Stem diameter was significantly less for the CSP+1AA treatment than for CSP-1AA. This interaction was with the Athi soil. There were no significant interactions of Mwea and Kabete soils with CSP-lAA and CSP+1AA treatments with regard to stem diameter (Table 14). Soil depths did not significantly interact with these treatments to show any significant differences in the stem diameter (Table 15). Growth in stem diameter was significantly less for the control than for the other treatments on the Athi soil but had no difference on the other two soils. In fact the plants on control Kabete soil did slightly better than the treated ones (Table 16).

From data which were not tabulated, it was observed that both Athi and Mwea soils had tops weight which decreased with rate of CSP-lAA but which increased for Kabete soil. These effects were significant for Mwea and Kabete soils. CSP treatment caused significant increases in tops weight for all the soils compared with lAA (Table 12). This effect of CSP is further shown in Table 13 in which this treatment had the same contribution in


.0





8:1


Table 12.


Interactions for soils with response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP and lAA treatments


Soils Significant
difference
Treatment Athi Mwea Kabete


Mean values


0.05 level


Stem diameter, mm


CSP


1AA

Difference


5.7 3.1 2.6


5.8 5.0 0.8


0.47


5.7 5.1 0.6


Tops weight, g


CSP

lAA


Difference


CSP

1AA


23.1 16.9 6.2


Tops P, %

0.129 0.083


25.3 18.9

6.4


0.019


0.154 0.105


0.093 0.046 0.049


3.1


22.7

5.4 17.3


0.158 0.065


Difference





82


Table 13.


Interactions for soil depths on response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP and lAA treatments.


Soil depth, cm Significant
difference
Treatment 0-15 15-30


Mean values


0.05 level


Stem diameter, mm


CSP lAA


Difference


5.8

4.7


1.1


1.2


5.7

4.0 1.7


Tops weight, g


CSP lAA


Difference


Tops P, %


0.053 0.087


24.4 15.1 9.3


2.6


23.0

12.4 10.6


CSP 1AA


0.152 0.099


0.015


0.159 0.072


Difference






83




Table 14. Interactions of soils with response of eucalypt stem
diameter, tops weight, and tops P for comparison of
mean CSP, lAA and CSP plus 1AA treatments.


Soils
Athi Mwea Kabete
Means


Significant difference
0.05 level


CSP-lAA CSP+1AA


Difference



CSP-lAA CSP+1AA


Difference


5.7
4.4 1.3



22.6

14.1 8.5


Stem diameter, mm

5.7
5.4 0.3

Tops weight, g

22.8 2

20.0 2


2.8 -


Tops P, %


CSP- 1AA CSP+1AA


Difference


0.157

0.112 0.045


0.135 0.106 0.029


3.1


1.6

2.1 0.5


0.019


0.153 0.150 0.003


Treatment


0.47


5.5
5.4 0.1






84


Table 15.


Interactions for soil depths on response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP-lAA and CSP plus lAA treatments.


Soil depths Significant
Treatment 0-15 15-30 difference


0.05 level


CSP-* lAA CSP+lAA


Difference


Means
Stem diameter, mm


5.6 5.3 0.3


1.2


5.7

4.8 0.9


Tops weight, g


21.2 19.8


Difference


1.4


Tops P, %

0.161 0.125


23.4 17.7 5.7


0.015


0.153 0.116


0.036 0.037


CSP- 1AA CSP+1AA


2.6


CSP- LAA CSP+IAA


Difference




Full Text

PAGE 1

GROWTH AND CCMPOSITION OF EUCALYPTUS AND MAIZE ON KENYA SOILS FERTILIZED WITH PHOSPHATE AND INDOLE ACETIC ACID BY Joseph Kipkorir A. Keter A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 1981

PAGE 2

ACKNOWLEDGMENTS I wish to express my deep indebtedness to Dr. J. G. A. Fiskell, the chairman of my supervisory committee, for his kind advice and guidance in my research. I also thank Drs. V. W. Carlisle, H. L. Popenoe, W. L. Pritchett, D. F. Rothwell, and P. V. Rao members of my supervisory committee for their helpful suggestions in this study. 1 express my special thanks to Rebecca Peck and Dr. F. G. Martin for their helpful evaluation of the data. I gratefully acknowledge the assistance and help I got from Frank Sodek, Dave Cantlin, Mary McLeod, Craig Reed, and Lee Jacobs for some of the laboratory assistance. I acknowledge Patricia Liebich for typing this dissertation. 1 thank my wife, Mary, for her support and sacrifices during the tenure of this study, and to my daughter Winnie for making our stay here joyful. ii

PAGE 3

TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ii LIST OF TABLES v ABSTRACT xv INTRODUCTION 1 LITERATURE REVIEW 7 Phosphorus 7 Occurrence of Phosphate Minerals 7 Inorganic Phosphorus in Soils 7 Reactions of Phosphorus in Soil 9 Adsorption Reactions 11 Movement of Phospliate Ions in Soil 13 Mechanisms Affecting Ion Distribution 17 Effectiveness of Phosphate Fertilizers 22 Pelletized Pliosphate 24 Phosphate Placement 25 Fluid Fertilizers 29 Residual Phosphorus in Soils 30 Maize 33 Utilization of Phosphorus 33 Ifesearch in Kenya 34 Indole Acetic Acid in Maize 34 Eucalyptus 41 Classification 41 The Eucalypts Range of Growing Conditions 43 Eucalypts as an Exotic Plant 44 Eucalyptus grandis 45 Site Quality 4ft I'e rt I 1 1 zcÂ’rs 47 Container-Grown Seedlings 48 Types of containers 49 MATERIALS AND METHODS 51 Soil Properties 51 Soil Preparation 52 Eucalyptus Experiment 53 Maize Experiment after Eucalyptus 54 Maize Experiment with Two Soils 54 Analytical Methods 55 Reagents for P Determination 56 Soil Extraction 57 iii

PAGE 4

Page Extraction of Plant Tissue 58 P Determination 59 Statistical Analysis 60 RESULTS AND DISCUSSION 62 Eucalyptus Experiment 62 Soils 62 Growth Factors 62 Maize Experiment after Eucalypt 91 Growth Factors 91 Maize Experiment with Two Soils, Athi and Kabete, Treated with Fresh CSP and lAA 110 Growth Factors 110 REGRESSION RELATIONSHIPS 124 (i) Eucalyptus Experiment 125 (ii) Maize, Residual Soil Treatments 127 (iii) Maize, New Treatments 128 CONCLUSIONS 130 APPENDIX 133 LITERATURE CITED 192 BIOGRAPHICAL SKETCH 205

PAGE 5

1 2 3 4 5 6 7 8 9 10 11 12 13 63 65 67 68 69 70 71 72 73 77 79 81 82 LIST OF TABLES Some properties of soils from Kenya Means and significant height responses for Eucalyptus grandis grown on three soils treated with lAA and CSP Soil X treatment means for CSP forms x rate quadratic effects found for eucalypt height at 2 months Interaction of soils for lAA and CSP comparison for eucalypt height at three times Mean effect of soil depth on eucalypt height in response to lAA and CSP alone Interaction of soils on comparison of mean eucalypt height for CSP with lAA (CSP-IAA) and CSP+IAA Interaction of soil depths on comparison of mean eucalypt height for CSP-IAA and CSP+IAA Mean effect of soils on eucalypt height, comparing controls with the other treatments Mean effect of soil depth in eucalypt height on control compared to other treatments Means and significant stem diameter, weight of tops, and tops P of Eucalyptus grandis grown on three soils treated with lAA and CSP Interactions of soils with response of eucalypt tops P to CSP rates Interactions for soils with response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP and lAA treatments Interactions for soil depths on response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP and lAA treatments V

PAGE 6

Table Page 14 Interactions of soils with response of eucalypt stem diameter, tops weight and tops P for comparison of mean CSP-IAA and CSP plus lAA treatments 83 15 Interactions for soil depths on response of eucalypt stem diameter, tops wciglit, and Lops P for comparison of mean CSP-IAA and CSP plus lAA treatments 84 16 Interaction of soils with response of eucalypt stem diameter, weight of tops, and tops P for comparison of control with other treatments 85 17 Means and significant responses for leaf P (in two soils) of Eucalyptus grandis and soil test P by DA and SB methods for three soils treated with lAA and CSP 88 18 Interaction of soils on mean DA-P values for linear response to CSP treatments for eucalypt 90 19 Interaction of soil depth with DA-P extracted from soils for eucalypt for CSP form comparison 90 20 Interactions of soils on DA-P and SB-P for treatment comparison of CSP with lAA for soils used for eucalypt 92 21 Means and height of Zea mays responses to residual lAA and CSP applied to three soils 94 22 Interaction of soils with maize height at 4 weeks for comparison of linear response to CSP rates 96 23 Interaction of soils with maize height at 4 weeks for comparison of linear response to (JSP-IAA rates 96 24 Interaction of soils with maize lielght at 4 weeks for comparison of response to CSP and lAA alone 96 25 Interaction of soil depths on maize height at 6 weeks comparing linear response to CSP-IAA rates 99 26 Interaction of soils on maize height at 6 weeks comparing CSP with lAA treatments al6ne 99 vi

PAGE 7

27 28 29 30 31 32 33 34 35 36 37 38 39 40 Page 100 102 102 105 106 107 107 108 108 111 113 115 116 116 Means and responses of tops weight and tops P of Zea mays and of soil test (DA) P to residual lAA and CSP treatments of three soils Interaction of soils with maize tops weight for comparison of CSP forms Interaction of soils with maize tops weight, tops P, and DA-P for comparison of linear effect of CSP rates Interaction of soils on maize tops weight, tops P, and DA-P for linear response to CSPÂ’IAA rates Interaction of soils on maize tops weight, tops P, and DA-P for comparison of CSP and lAA alone Interaction of soils on maize tops weight, and DA-P for comparison of CSP-IAA and CSP+IAA treatments Interaction of soils on maize tops weight, tops P, and DA-P for comparison of control with the other treatments Interaction of soil depths on DA-P extracted for comparison of CSP forms Interaction of soil depths on DA-P extracted for comparison of linear response to CSP forms Means and significant responses for Zea mays height during 6 weeks grown on two soils treated with lAA and CSP Interaction of soils on maize height at 4 and 6 weeks for comparison of CSP to lAA treatments alone . . Means and significant yield and tissue P responses for Zea mays grown on two soils treat with lAA and CSP Interaction of soils on maize tops yield and tops P for comparison of linear effect of CSP rates Interaction of soils on maize tops for comparison of linear effect of CSP-IAA rates vii

PAGE 8

Page Table 41 Interaction of soils on maize tops P for comparison of CSP and lAA treatments 115 42 fn ternc t i on of soils on inn I zo lops IÂ’ for coiiipaiison ol other treatments with the control ny 43 Interaction of soils on maize leaf P for comparison of CSP forms Hg 44 Means and responses of root weight, and root P of 2ea mays and of double acid-extractable soil P for two soils receiving three rates of lAA and CSP sources 12 i 45 Interaction of soils on maize root P for comparison of linear effect of CSP rates 122 46 Interaction of soils on maize root P and DA-P for comparison of linear effect of CSP-IAA rates 122 47 Interaction of soils on maize root P for comparison of CSP with lAA treatments 123 48 Interaction of two soils on DA-P extracted in the maize experiment for edmparison of quadratic effect of CSP rates 123 49 Correlation between yields and corresponding plant and soil P values 124 50 Mean height and stem thickness of eucalyptus grown on 0to 15-cm depth of Athl soil treated with indole acetic acid (lAA) and three concentrated superphosphate (CSP) sources at three rates 133 51 Mean height and stem thickness of eucalyptus grown on 15to 30-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 134 52 Mean height and stem thickness of eucalyptus grown on 0to 15-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 135 viii

PAGE 9

53 54 55 56 57 58 59 60 61 62 Page Mean height and stem thickness of eucalpytus grown on 15to 30-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 136 Mean height and stem thickness of eucalyptus grown on 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 137 Mean lieight and stem thickness of eucaiyi)tus grown on 15to 30-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates .....138 Mean dry matter yield of eucalyptus tops from eucalyptus grown on three Kenya soils sampled at two depths and treated with indole acetic acid (lAA) and three concentrated superphosphate (CSP) sources at three rates.. 139 Mean analysis of eucalyptus tops sampled from 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates .. 140 Mean analysis of eucalyptus tops sampled from 15to 30-cm depth on Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates.. 141 Mean analysis of eucalyptus tops sampled from 0to 15-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. 142 Mean analysis of eucalyptus tops sampled from 15to 30-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates i 143 Mean analysis of eucalyptus tops sampled from 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 144 Mean analysis of eucalyptus tops sampled from 15to 30-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 145 ix

PAGE 10

Table Page 63 Mean analysis of eucalyptus leaves sampled from eucalyptus trees grown on the 0to 15-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 146 64 Mean analysis of eucalyptus leaves sampled from eucalyptus trees grown on the 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 147 65 Mean analysis of 0to 15-cm depth of Athi soil sampled after eucalyptus growth treated with indole acetic acid (lAA) and three concentrated superphosphate (CSP) sources at three rates 148 66 Mean analysis of 15to 30-cm depth of Athi soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 149 67 Mean analysis of 0to 15-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 150 68 Mean analysis of 15to 30-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 151 69 Mean analysis of 0to 15-cm depth of Kabete soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 152 70 Mean analysis of 15to 30-cm depth of Kabete soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 153 71 Mean analysis of 0to 15-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 154 X

PAGE 11

72 73 74 75 76 77 78 79 80 81 82 Page 155 156 157 158 159 160 161 162 163 164 165 166 Mean analysis of 15to 30-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates Mean height of maize grown on 0to 15-cm depth of undisturbed Athi soil with treatments previously used for eucalyptus Mean height of maize grown on 15to 30-cm depth of undisturbed Athi soil with treatments previously used for eucalyptus Mean height of maize grown on 0to 15-cm depth of undisturbed Mwea soil with treatments previously used for eucalyptus Mean height of maize grown on 15to 30-cm depth of undisturbed Mwea soil with treatments previously used for eucalyptus Mean height of maize grown on 0to 15-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus Mean height of maize grown on 15to 30-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus Mean dry matter yield of maize tops grown on Kenya soils undisturbed after treatments previously used for eucalyptus Mean analysis of maize tops sampled from 0to 15-cm depth of undisturbed Athi soil with treatments previously used for eucalyptus Mean analysis of maize tops sampled from 15to 30-cm depth of undisturbed Athi soil with treatments previously used for eucalyptus Mean analysis of maize tops sampled from 0to 15-cm depth of undisturbed Mwea soil with treatments previously used for eucalyptus Mean analysis of maize tops sampled from 15to 30-cm depth of undisturbed Mwea soil with treatments previously ysed for eucalyptus xi

PAGE 12

85 86 87 88 89 90 91 92 93 94 95 168 169 170 171 172 173 174 175 176 177 178 Mean analysis of maize tops sampled from 0to 15-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus Mean analysis of maize tops sampled from 15to 30-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus Means and treatment comparisons for various elements in tops of Zea mays grown on three soils having residual lAA and CSP treatments Mean analysis of 0to 15-cm depth of Athi soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus Mean analysis of 15to 30-cm depth of Athi soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus Mean analysis of 0to 15-cm depth of Mwea soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus Mean analysis of 15to 30-cm depth of Mwea soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus Mean analysis of 0to 15-cm depth of Kabete soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus Mean analysis of 15to 30-cm depth of Kabete soil sampled after maize growl li on undisturbed sol] containing prior tri'al meul s f
PAGE 13

Page Table 96 Mean dry matter yeild of maize tops and roots from maize grown on 0to 15-cm depth of Athi and Kabete soils treated with indole acetic acid and three concentrated superphosphate sources at three rates 179 97 Mean analysis of maize tops sampled from 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 180 98 Mean analysis of maize tops sampled from 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 181 99 Significant factors of the analysis of variance for maize tops responses to two soils treated with lAA and CSP 182 100 Mean analysis of maize leaves sampled from maize grown on the 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 183 101 Mean analysis of maize leaves sampled from maize grown on the 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 184 102 Significant factors of the analysis of variance of maize leaf responses to two soils treated with lAA and CSP 185 103 Mean analysis of maize roots sampled from maize grown on the 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 186 104 Mean analysis of maize roots sampled from maize grown on the 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates 187 105 Significant factors of the analysis of variance of maize root responses to two soils treated with lAA and CSP 188 106 Mean analysis of 0to 15-cm depth of Athi soil sampled after maize growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 189 xiii

PAGE 14

Page Table 107 Mean analysis of 0to 15-cm depth of Kabete soil after maize growth treated with indole acetic acid and three concentrated superphosphate sources at three rates 2^90 108 Significant factors of the analysis of variance for eucalypt tops in response to three soils treated with lAA and CSP iqi xiv

PAGE 15

Abstract of Dissertation Presented to the Graduate Council of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy GROWTH AND COMPOSITION OF EUCALYPTUS AND MAIZE ON KENYA SOILS FERTILIZED WITH PHOSi'lIATE AND INDOl.E ACl'TIC ACID By Joseph Kipkorir A. Keter August, 1981 Chairman: John G. A. Fiskell Major Department: Soil Science Three glasshouse experiments were conducted with three Kenya soils to determine plant responses to exogenous indole acetic acid (lAA) at 31, 62, and 124 g/ha and to concentrated superphosphate (CSP) in powder, pellet, or pellet (including lAA) forms applied at 28, 56, and 112 kg P/ha. Soils were taken from depths of 0 to 15 and 15 to 30 cm and two soils were Vertisols (Athi and Mwea) and the other a Latosol (Kabete). The soils were nearly similar in pH (6-3 to 6-8) but differed in soil test P by the double-acid method (DA-P) with values of 4-5, 7-0, and 550 ppm P for Athi, Kabete, and Mwea soils, respectively. Soil test for P by 0*5 ^ sodium blcarbon.ate (SB-P) was also used for Athi and Kabete soils. Eucalyptus grandis was planted in the first experiment and early growth exhibited purplish leaves and stems on Athi and XV

PAGE 16

Kabete soils, particularly without P added, attributed to P deficiency. At 2, 3, and 4 months, height of plants was greater where CSP was used compared to lAA and differed between soils, lops weight, stem diameter, and tops P were significantly greater where CSP was present but only tops P' increased with the amount of CSP forms applied. For each soil h Iglil y significant linear regressions were obtained between tops P and either DA-P or SB-P, tops P and leaf P, and DA-P and SB-P. Fertilization with 28 kg P/ha resulted in tops P or leaf P above 0*110%. On the above soils left undisturbed, Zea mays L. of cultivar 'Pioneer 3160' was planted. Plant height, tops weight, and tops P increased linearly with previous CSP rates and were lower for lAA. Highly significant linear regression relationships were found between tops P and DA-P for each soil and at each soil depth. Another study with maize after preplant fertilization of Athi and Kabete soils showed that root weight was higher where CSP was present and root P was less than leaf P or tops P. XVI

PAGE 17

INTRODUCTION The greatest challenge facing most developing countries, especially those in tropical Africa, is the ability to (i) produce enough food for its people, and (ii) control the population growth. These countries have numerous other problems such as unstable governments, inadequate health care, too much dependence on foreign countries for most of the manufactured goods, high illiteracy, and failure to make full and wise use of the available natural resources. Agricultural production in the tropics is principally controlled by rainfall, for in equatorial regions the temperature is fairly constant over the year. In most areas, the rainfall is never uniformly distributed throughout the year. Near the equator there are typically two rainy seasons a year. The outstanding characteristic of the rainfall over most of tropical Africa from the agricultural point of view is that, averaged over the year, it is less than the amount of water a crop well-supplied with water would transpire. It is, therefore, necessary to restrict crop production to the rainy seasons or choose crops which will not suffer too severely if subjected to considerable periods of drought. Agricultural production in the tropics can be intensified by deveJopIiig metlioclH for eiiHurlng Llie bent tiHi> of rain fa I I s on the land. These methods can be grouped into three categories: foremost are those which enusre that as much as possible of the 1

PAGE 18

2 rain percolates into the soil, at least up to the amount the growing crop needs for a good yield. Secondly, those methods involving the choice of a crop and its management are needed so that its yield is as high as possible from the water that is actually available. Thirdly, there are those methods in which a crop is chosen and managed in order to minimize the harmful effects of drought during its growing season. These methods will not be considered in detail here but were only mentioned in order to specify further the agricultural problems of semi-arid areas of the tropics. Semi-arid areas are not characterized by low rainfall every year, so that, in a certain proportion of years in these areas, crop yields are more influenced by the level of soil fertility than by the availability of water. In most areas phosphate and nitrogen are the nutrients most likely to limit crop yields. In many areas of tropical Africa, the soils appear to be very low in phosphate, and crops usually respond well to phosphate fertilizers. It is now well-established that a phosphate fertilizer applied to a soil low in phosphate will increase yields for a number of years after application. Effectiveness of P fertilizers is dependent upon chemical and physical characteristics of the fertilizer, rate of its use, and method of its application. Soil and climatic conditions under which the crop is grown, and crop characteristics also influence the effectiveness of P fertilizer.

PAGE 19

3 Phosphorus fertilizers can be classified into three groups on the basis of their solubilities, namely: (i) those in which the P is mostly soluble in water, (il) those not readily soluble in water but soluble in ammonium citrate, and (ill) those Insoluble in ammonium citrate. Usually, the sum of (i) and (ii) represents the so-called available P. It is found highly desirable to granulate fertilizers in order to facilitate handling and application and, possibly, also influence the agronomic value of the fertilizer in some cases. Granule size may influence fertilizer effectiveness in two ways. First, it affects the placement pattern or distribution of fertilizer in the soil; and second, it determines the effective surface area and the reactivity of the material. Reaction of P with the soil to form largely insoluble products is less likely to be a limiting factor than rate of P dissolution in the case of slightly water-soluble P fertilizers. Consequently, small granules which provide a large surface area and ensure closer contact with and better distribution through the soil are generally assumed to be more effective than large granules. But in the case of highly water-soluble phosphates, rate of dissolution generally is of less concern than reversion or reaction with the soil to form less soluble compounds. The rate of P reaction with the soil tends to be less with large than with small granules. Another factor that is important in considering water solubility and granule size relationships is method of application

PAGE 20

4 of the fertilizer. Banding of the fertilizer tends to minimize contact and reaction with the soil. The zone of diffusion around a band becomes an enlarged version of the zone around a coarse granule. Such application tends to accentuate the value of a high degree of solubility. Broadcasting the fertilizer and mixing it with the soil maximizes fertilizer and soil reaction and favors the less soluble sources. The study of growth control mechanisms is one of the most active fields of plant physiology. It is now evident that growth is controlled not by one but by several groups of hormonal substances as well as by numerous naturally occurring inhibitors which are still very incompletely understood. Tnformntion on Indole acetic acid ( lAA) , one ol Llie must widely studied substances, shows that it is produced mainly in meristematic and growing regions of shoots; senescent tissue has also been suggested. lAA is found in most tissues. It moves readily from shoots to roots in phloem and more slowly by cell to cell by polar-transport, basipetally in shoots and acropetally in' roots. lAA promotes elongaLlon of Hlemn and eoleopLllea, pliotoand ge'ot rop I c curvature, adventitious rooting and lateral root initiation, xylem differentiation, fruit growth, cambium activity and leaf epinasty. However, it can inhibit root elongation, leaf senescence and fruit abscission. Production of lAA is inhibited by Zn and P deficiencies and increased by gibberellins and cytokinins.

PAGE 21

5 In maize crops, there is a close relationship between high-producing varieties, fertilizer, plant population and moisture condition of the soil. Another extremely important factor, particularly under African conditions isi early planting, which means planting at the start of the rains. In Kenya, it has been found that planting after the rain has started causes significant reduction in yields. The actual size of the reduction in yield will vary according to such circumstances as the rainfall pattern and the soil characteristics. If the rainfall is not very heavy, and the soil has good structure and drains quickly, then the decline in yield from late planting will be smaller than if the rainfall is heavy, and the soil has poor structure and drainage. For that reason, intensive soil cultivation with the ploughing in of maize stover, is practiced where possible, in order to improve soil structure, and good soil drainage which are of the utmost importance. Phosphorus promotes the development of the i root system, aids in seed formation and hastens ripening of maize. The maize plant has a coarse, fibrous root system which spreads widely and penetrates deeply. Nevertheless the young plant has difficulty in taking up phosphorus from the less available phosphate forms in the soil. Maize is, therefore, often used as a test-plant to estimate the amount of easily available P in a soil. In order to stimulate early growth and development care should be taken to provide the crop with a sufficient amount of easily available P.

PAGE 22

6 The need to stimulate modern agriculture is urgent in Africa because the population is increasing at a faster rate than is food production. Most African countries import paper and yet they could produce trees such as eucalypt for their timber and paper needs. Cost of importing fertilizer and lack of capital restricts improvement of crop yields. There is need to use P fertilizers efficiently and effectively. If a method could be found to stimulate rooting of seedlings and early plant growth, this might also increase the efficiency of applied P by causing more root intercept of available P. The present study was done with three Kenya soils in order to test if indole acetic acid could assist in improving the response of two test crops to P fertilization by stimulating root proliferation and plant growth. To check this hypothesis, pelletized CSP was made containing 100 ppm of indole acetic acid (lAA) . The experiments consisted of three rates of CSP containing lAA compared to lAA without P. , The effect of pelletized CSP without lAA was compared to CSP in powder form to be determine if pelletized CSP caused a different plant response. The first experiment was conducted with Eucalyptus grand is using three rates of lAA, and three rates of three CSP sources to check on the response to lAA and to pelletized P. The objective of the second experiment was to test for residual effects of CSP and lAA on Zea mays gro^vn on these soils. The third objective was to determine if CSP and lAA or in combination applied preplant had an effect on maize responses.

PAGE 23

LITERATURE REVIEW Phosphorus Occurrence of Phosphate Minerals Phosphate minerals form under a wide variety of environmental conditions ranging from silicate melts, to natural soils, to ocean floors. In nearly all naturally occurring phosphates, P is pentavalent, even though tri-, quadri-, and hexavalent-P compounds are readily synthesized (Lindsay and Vlek, 1977). X-ray diffraction has made it possible to determine the crystal structures of most orthophosphates. It was observed that the central P atom is surrounded by four 0 atoms forming an approximately tetraliedral structure (Lindsay and Vlek, 1977). This configuration is possible because of the formation of four o— bonds after sp3 hybridization and additional IT-bonding using d-orbitals. The structural formulas of these compounds are represented as having a double bond in order to satisfy classical valency requirements, but some sharing of the multiple-bond character occurs among tlie four 0 atoms. The formation of stable atomic structures containing PO4 tetrahedra is naturally accomplished through the high affinity of PO4 for cations, particularly those exhibiting eightfold coordination. Inorganic Phosphorus in Soils . , Inorganic phosphorus in soils is believed to exist as sparingly soluble orthophosphates of Al, Fe and Ca. The Ca-P compounds such 7

PAGE 24

8 as apatites are of primary origin. Al— and Fe-P, such as variscite (A 1 P 04 2 H 20 ) and strengite (FeP 04 * 2 H 20 ) are generally believed to be the predominating ultimate end-products of inorganic P formed during soil genesis and P fertilization (Chakravarti and Talibudeen, 1962; Chang and Chu, 1961; Chang and Jackson, 1958; Hawkins and Kunze, 1965; Kittrick and Jackson, 1956; Lindsay ^ , 1959; Taylor et al . , 1963; Yuan et al . , 1960) . Soil test correlation studies have shown that, in acid soils, the Al-P fraction as determined by Chang and Jackson's procedure (1957) is more available to upland crops than the Fe-P fraction. There is evidence that the Ca-P fraction is the least available of the three fractions (Chang and Juo, 1963; Hanley, 1962; Payne and Hanna, 1965; Susuki ^ al. , 1963; Smith, 1965). In soil, most of the inorganic P occurs in the clay fraction from which it cannot be separated by physical methods (Larsen, 1967). Consequently, direct evidence of the nature of the inorganic P cannot be obtained by known petrographic methods. Only when P has been separated from the soil (or formed in layers or pockets in the soil by natural processes) can a sufficient concentration of P minerals be obtained for direct petrographic examination. So far, only the P minerals apatite, vivianite (Fe 3 (P 04 ) 2 ' 8 H 20 ) and wavellite (AI 3 (OH) 3 (PO 4 ) 2 ' 5 H 2 O) have been qualitatively determined in soil by such metliods (Black, 1957). A semiquantitative method for the direct determination of soil apatite was developed by Shipp and Matelski (1960) . Although this method provides a direct way of detecting apatite minerals.

PAGE 25

9 it does not distinguish between the various forms of apatite, such as f luoroapatite and hydroxyapatite. Chang and Jackson (1957) attempted to classify inorganic soil P into different fractions, according to their extractability in various reagents. Since the reagents are very likely to cause a redistribution of the phosphorus during the extraction, such methods must be arbitrary. In view of this, the compounds reported to be in the soil may not have been actually present in the original soil. Reactions of Phosphorus in Soil Lehr and Brown (1958) and Lehr al^. (1959) identified CaHPOij* 2 H 20 (dicalcium phosphate dihydrate), CaHP 04 (dicalcium phosphate anhydrous), Ca 4 H(P 0 i,) 3 • 3 H 2 O (octocalcium phosphate) , and apatite in soils following the application of superphosphate. The particular compounds formed depended upon soil properties. Moreno ^_t aJ . (1960a, 1960b) determined the solubility and stability of dicalcium phosphate dihydrate and octocalcium phosphate. Cole and Jackson (1950, 1951) made preparations of AlPOi,'2H20 (variscite) , FePOi* *21120 (strengite) and other compounds and hypothesized their probable formation in soils was as phosphate fixation products. Haseman ^ (1950, 1951) showed that under certain conditions complex crystalline phosphates of iron and aluminum were formed when clays or iron and aluminum oxides reacted with phosphate solutions. Kittrick and Jackson (1955) reacted soil minerals with phosphate solutions and, by use of the electron microscope, presented evidence of the formation of new P, crystalline phases .

PAGE 26

10 Lindsay and Stephenson ( 1959 ) repeatedly reacted a series of soil samples, first with a solution saturated with respect to Ca(H2P04) 2 • H2O (monocalcium phosphate monohydrate) and CaHP0i,2H20 (MTPS, that is, metastable triple-point solution), and later with water, in an attempt to simulate the changing chemical environment of soil surrounding a superphosphate granule. They found that the reaction of MTPS with soil was accompanied by an increase in pH and precipitation of Fe, Al, and Ca phosphates from solution. Soil repeatedly contacted by MTPS gradually became more acidic and showed continued dissolution of Fe and Al. Subsequent additions of water to the soil residues remaining after reaction with MTPS increased the pH and caused further precipitation of phosphate from solution. Many filtrates obtained during these reactions yielded precipitates upon standing. They identified the following crystalline compounds from these precipitates: CaHP 04 2 H 20 , HgKaAl 5 (PO4 ) s ' I8H2O HeK(Al,Fe) 3(P04) 6‘6H20, and CaHP04 Lindsay and Stephenson ( 1959 ) also suggested that the indications are that these compounds may form as initial phosphate reaction products of superphosphate fertilizers in soil. Bell and Black ( 1970 ) compared the methods for identifying crystalline phosphates produced by interaction of orthophosphate fertilizers with soil. In soils that were treated with Ca (H2PO4 ) 2 • H2O , NH4H2PO4, and (NH4)2HP04, various methods were investigated. These ranked as follows in decreasing order of sensitivity-optical examination of soil — optical examination of

PAGE 27

n glass fiber filter paper inclusion > X— ray diffraction examination of glass-fiber filter paper inclusion > X-ray diffraction examination of soil. Adsorption Reactions The reaction of fertilizer P with soil depends upon the nature and amount of adsorbing surface as well as pH and other factors. Olsen and Watannbe (1957) found that adsorption of P by soils from dilute solutions showed a closer agreement with the Langmuir isotherm than with the Freundlich curve. The adsorption maximum calculated from the Langmuir isotherm was closely correlated with the surface area of soils as measured by ethylene glycol retention. Regression analysis of phosphorus adsorption as a function of five soil characteristics indicated that organic matter is important in the initial bonding of P by soils (Harter, 1969). He proposed that P is initially bonded to anion exchange sites on organic matter, and subsequently transformed into less soluble iron and aluminum phosphates. Rajan and Fox (1975) studied phospliate adsorption by several Hawaiian and Indian soils, and the relation of phosphate adsorption to hydroxyl, sulfate, and silicate ions released In two Hawaiian soils. Adsorption isotherms of some of the soil showed an abrupt increase in pliosphate adsorption at high concentration. They analyzed the isotherms by applying a binary Langmuir equation (assuming two types of sites). They observed that phosphate adsorption is associated with increased pH and sulfate

PAGE 28

12 release at low levels of phosphate adsorbed and increased silicate release throughout. According to Rajan and Fox (1975), these observations suggest that, at low concentrations, phosphate exchanges with (i) adsorbed sulfate and adsorbed silicate, and (ii) with water and hydroxyls of metal hydrous oxides and edge Al of clays. At high concentrations, additional phosphate is adsorbed by displacing the structural silicate of clays. The increase in phosphate adsorption by structural silicate release, over that of surface exchange reactions, was about 50 and 25% in two soils containing kaolinite and allophane, respectively. Mekaru and Uehara (1972), using the difference in pH of a soil suspension prepared with IN KCl with water to determine net charge of colloids with constant potential type surface, found that the quantity , called delta pH, had a positive, zero, or negative value corresponding to the net surface charge. Negative and positive adsorption of chloride or nitrate ions were measured in soil suspensions with negative and positive delta pH, respectively. They found that increasing the nitrate ion concentration increased sulfate adsorption in suspensions with negative delta pH values. Negative adsorption of nitrate and chloride ions was measured when sulfate ions were added to a soil colloidal suspension which had initially a net positive charge. Their belief that specifically adsorbed anions render a surface more negative by displacing the zero point of charge to lower pH values was supported in their observations.

PAGE 29

Furthermore, this was substantiated by a measured increase in cation exchange capacity (CEC) over an initial value of 26 meq/lOOg in a phosphated soil. Each millimole of adsorbed phosphate increased the soil CEC by 0.8 meq. Langmuir plots of ! adsorption Isotherms of four soils were shown to fit into two intersecting lines (Taylor and Ellis, 1978). These workers investigated the mechanism of P adsorption on soil and anion exchange resin surfaces at low equilibrium concentrations. The adsorption data were also found to fit the BET (Brunauer, Emmett, and Teller) equation. The monolayer capacities computed from the BET equation were found to correspond closely with the adsorption maxima computed from the initial slopes of the Langmuir plots. Taylor and Ellis (1978) concluded that, at low concentrations, P was bonded by two points of attachment after deprotonation of the H 2 PO 4 ion, followed by one point of attachment at higher P concentrations during adsorption on the resin surface. This resulted in the deviation from linearity predicted by the Langmuir equation. Moveme nt o f E_h_o splim to. Io ns in So l I The mobility of P applied as dianmionium orthophosphate (DAP), triammonium pyrophosphate (TPP) , or ammonium polyphosphate (APP) was studied by Khasawneh et al . (1974) in columns of a fine sandy loam. They observed dissolution of the fertilizer in soil moisture that moved towards the P-application site. This water movement was sometimes against a gradient in soil moisture content, but it was along a gradient in the total potential of soil water.

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14 They found that the extent of P movement from all three sources was similar, but that the distribution patterns were different. The extent of P movement was influenced more by the initial soil moisture content than by the source of P. They also noted that a higher fraction of the added P was precipitated when the source was TPP or APP than when it was DAP. The ability of the polyphosphates to sequester soil Fe and A1 did not prevent the precipitation of these phosphates nor did it make them more mobile than the orthophosphates. They found APP only delayed the precipitation reaction to a degree that depended on the polyphosphate content of the fertilizer material. Hydrolysis and sorption of pyroand poly-phosphates in soil have been studied by many workers. Sutton and Larsen (1964) and Sutton ^ (1966) measured rates of hydrolysis of pyrophosphates in soil, and found that hydrolysis was largely enzyme-mediated and related to the overall biological activity as measured by CO 2 evolution. Gilliam and Sample (1968) found that either sterilizing soil by fumigation with CHaBr or by autoclaving did not completely stop hydrolysis, indicating that chemical as well as microbial factors in the soil determine the rate of pyrophosphate hydrolysis. Hashimoto et (1969) reported that hydrolysis ceased when concentration of pyrophosphates in a soil suspension exceeded 0.2M. They also , reported that pyrophosphate was adsorbed more strongly than orthophosphate on soils and clay minerals. Sutton and Larsen (1964) had reported just the opposite for soils in England. Their data indicated that

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15 ortho-phosphate was adsorbed more strongly than pyrophosphate by soil, but that these soils had higher adsorption capacity maxima for pyrophosphate than for orthophosphate. Khasawneh ^ (1974, 1979 -) discussed the comparative mobility of orthoand polyphosphates in soil and related it to two soil processes : (i) reactions of these phosphates with soil, and (ii) biologically catalyzed hydrolysis of the poly-phosphates. In their view, diffusive movement of phosphates away from granule or band sites is basically by salt diffusion where equivalent amounts of cations and phosphatic anions are involved. They reasoned that since fertilizer solution is initially very concentrated in both phosphates and NH 4 '*' , subsequently NH^ readily replaces exchangeable cations, such as Ca, Mg, K, and Al. These cations, however, when combined with orthophosphates form salts that are rather Insoluble and may be rapidly precipitated in situ in soil, or their precipitation may be delayed to the extent that if the solution phase is separated from the soil, precipitation occurs thereafter (Lindsay £t al. , 1962). Lindsay ^ al. (1962) reported that considerable amounts of soil Fe and Al were dissolved by solutions of ammonium orthoand polyphosphates, indicating that reaction of concentrated solutions of ammonium phosphates is not limited to exchangeable cations. For example, ammonium polyphosphate solutions dissolved 63 ymoles of Fe/liter and 8 ymoles of Al/liter when added to Fe 203 ‘H 20 and A 1 ( 0 H) 3 , respectively. Hashimoto £t al. (1969) reported that 25 ml of a 2.0M solution of triammonium pyro-phosphate dissolved

PAGE 32

16 65 mg of A1 from gibbsite and 10 mg of Fe from goethite in a 2-day period. They found that similar solutions were much less reactive with kaolinite and montmorillonite. In a study on the effects of cations associated with reactions of ammonium orthoand poly-phosphate fertilizers in soil, Sample ^ (1979) found that, in general, the ions derived from the fertilizer salts moved in association with the phosphate anions in the form of salt diffusion, and also moved by counter diffusion in exchange for some of the exchangeable soil cations. Exchangeable Ca in the first 6 mm of soil contacted by the fertilizer solution from diammonium phosphate (DAP) was replaced by NH 4 , and the displaced Ca^'f was precipitated in place by phosphate. Displaced Ca was transported in the fertilizer solution of triammonium pyro-phosphate monohydrate (TPP) and ammonium polyphosphate (APP) for 6 to 8 mm before it was precipitated. Reactions of phosphates with displaced Ca^'*Â’ caused its activity in these soil zones to drop sharply and created a Ca gradient opposite to that of the phosphates. They observed that depletion of exchangeable cations, especially at or just beyond the fertilizer solution front, caused soil pH to drop as much as one pH unit below the initial soil value. Within the soil zone affected by phosphates, pH was about 7.5 with DAP and 6.7 to 7.2 with APP and TPP. Differences in pH between soil in the outer zones reached by phosphates and the inner layers ranged from 1.7 to 2.7 pH units.

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17 In the study by Sample e_t ad. (1979), it was found that soil A1 was influenced greatly by all three fertilizer solutions so that with DAP , the reaction products simply reprecipitated in place without undergoing any movement. The observed increased acid extractability was the only evidence of the presence of fresh precipitates involving Al. They determined that in addition to such a reaction, movement of Al occurred with TPP and APP, and there was evidence of rather-well-def ined zones of precipitation involving Al pyroor polyphosphates. They did not find evidence to implicate Fe in reactions similar to those for Al. Mechanisms Affecting Ion Distribution Barber (1974b) discussed factors which affect ion movement in soil. Root Interception, mass-flow » and diffusion were considered as affecting ion distribution. They measured nutrients as concentration per unit volume of soil when diffusive flow to plant roots was determined. Hence they observed when the bulk density of soil is increased near the root, that the concentration of available nutrients per unit soil volume is also increased. This increase results in a greater concentration gradient for nutrients diffusing to the root (Barber, 1974b). They suggested that roots may also encounter some nutrients and absorb them as it forces its way through the soil. Oliver and Barber (1966) calculated tlic ions displaced by the roots as a supply mechanism, although some ions may be pushed away and return to the root by mass-flow and diffusion, they assumed that the amount of ions returning to the root would be in

PAGE 34

18 additon to the amount for mass-flow and diffusion. They found that the root did not influence soil bulk density near the root surface. Barber (1974b) stated that, since plant roots absorb water, Llicy c .'uiMcd ,'i flow of water from the sol I to tlu' root aiirlace and this water contains inorganic ions as well as soluble organic molecules. He reported that such ions are mass-transported to the root in the convective flow of the water and that the amount of ions reaching the root depends upon the rate of water flow to the root and the average ion content of this water. He also stated that when the concentration of a given ion at the root surface is reduced, a concentration gradient normal to the root is established because the ion diffuses toward the root due to the thermal motion of the particles. His research indicates that the ion supply to the root and the rate of uptake is largely regulated by the rate of diffusion. He considered that diffusion follows Pick's law, which is F = DAOc/8x), where F is the amount diffusing per unit of time, t; D is the diffusion coefficient; A is the area for diffusion; and 9c/9x is the concentration gradient. Since diffusion to a root is in radial coordinates, the appropriate equation becomes more complex. A simplified version of this equation was given by Passioura (1963) as F = A[(C-Co)Dk/ro] where C is the initial total concentration of the nutrient in the soil; Co is the concentration at the root surface; is the root

PAGE 35

radius; k is a raonotonically decreasing function of Dt/r^; and o t is the time that the sink has been operating. He/ considered that the soil reacts chemically with many of the nutrients that diffuse to the root and also physically makes the diffusion pathway more tortuous. The value of D in a soil reflects the reduction in rate of diffusion because of the chemical reaction and the increase in tortuosity because of physical factors (Barber, 1974). Nye (1968) proposed a simple method for calculating the value of D for phosphate ions as follows; D = DifiVi(dCi/dC) where Di is the diffusion coefficient of P in free solution (8‘9xl0 ® cm^/soc); fj the Impcdence or tortuosity factor; Vi the volumetric water content; and dCi/dC = Vb which is the reciprocal of the slope of the P adsorption isotherm. Rate of P diffusion from fertilizer applied at the soil surface was studied by Hira and Singh (1978) using Pick's Law of diffusion. They determined the diffusion coefficient of P from a knowledge of the tortuosity factor and P adsorption isotherm. Phosphorus diffusion coefficient calculated from Nye's equation did not prove suitable at very low or high concentrations of P at the soil surface. The P diffusion coefficient calculated from their experimental data Increased linearly with the square root of P concentration applied at the source. They stated that the P diffusion coefficient could be

PAGE 36

20 calculated from the equation, DiVifi , D = — g (Q) ^ where Q is the material applied uniformly on a surface (mg/cm^). Their predicted P concentration-distance profiles were found to be very close to the experimental values estimated by empJoylng a sectioning technique. Chien et al . (1980) derived a modified Elovich equation in the form of Ct = Co -(V3)ln(a3)-( V3)lnC^ where a and 3 are constants, t is time, and the term and Co are given below. They described the kinetics of dissolution of three phosphate rocks (North Carolina, central Florida, and Tennessee) in tliree soils (one soil from I’JorJda and two Nigerian soils). They compared the values of Co, a, and 3 in the equation with the dissolution rates of various phosphate rocks in a given soil or a given phosphate rock in various soils. In this case, Co is the maximum P concentration in the soil solution that a phosphate rock can provide in a soil (C^. is the P concentration at time t). Chien e^ al. (1980) found that Co increased as a increased and/or 3 decreased in a given system. They failed to find any significant effect of temperature on the dissolution of phosphate rock in the soil. This implied that P retention by the tropical soils treated with phosphate rock may be much less affected by temperature than when compared with water-soluble P fertilizers such as concentrated superphosphate.

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21 In a study of phosphate sorption by acid, sandy soil, Fiskell et (1979) measured phosphate sorption by two soils with time using a laboratory batch technique for a range of initial P concentrations in solution. They compared experimental data with results calculated using a two-site sorption-desorption model and found that, for contact times > an hour, they observed that P sorption in both the sandy soils could be described by assuming rapid and slow reversible reactions to occur simultaneously at two separate types of sorption sites. But for contact times < 60 minutes they found that the 2-site model did not describe the P sorption adequately. At the rapid and slow sorption sites, the orders of the forward reactions were fractional and first-order, respectively, with regard to the P concentration in solution. For a given soil, one set of rate coefficient values was sufficient to describe the solution phase concentration of P for several different initial concentrations. Chien and Clayton (1980) derived a simple modified Elovich equation in the form: q = (V6)ln(a6) + (V6)ln t where q is the amount of phosphate released or sorbed and a and B are constants and t is time. They attempted to fit various experimental data reported in literature that failed to conform to a single first order kinetic equation. Using this equation, they successfully described the data as a single straight line that covers the entire span of reaction time. They suggested that it appeared that constants a and 3 may be used for comparison of reaction rates of phosphate release or sorption in different soils.

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22 Effectiveness of Phosphate Fertilizers Terman (1957) reported that for 433 P rate and source experiments in 7 Southeastern states of the Unites States of America, the distributions of the coefficients of variation (CV) (or standard errors per plot in percent) for corn, cotton, legume, legume-grass hay and small grain were similar. It was found that C.V. values were negatively correlated with yield levels for all crops and standard errors per plot were positively correlated with yield for corn and alfalfa but not significantly for cotton and wheat. They noted that there were no consistent interactions between P sources and rates. Webb ^ £l. (1959) reported on field research dealing with the importance of water solubility of P in fertilizers applied broadcast and plowed under for corn. Highly water-insoluble sources tended to be slightly less effective in a few of these experiments. But their general conclusion was that, on the soils included in the study, the degree of water solubility of the P was not a significant factor in determining the effectiveness of fertilizers applied by this method. All of the experiments in tliat study happened to be located on acidic or nearJy neutral soils, which raised the question of whether similar results would have been obtained on calcareous soils. In later experiments, Webb £ t £ 1 . (1961) conducted five field experiments in which several slightly water-soluble P sources were compared with concentrated superphosphate (CSP) for use in broadcast applications for maize ( Zea Mays L.).

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23 These tests were located on calcareous soils which tested low in available P. Based on their effect upon the concentration of P in corn leaves and upon corn yields, CSP and dicalcium phosphate dihydrate were found to be the most effective sources, with the former being slightly superior. Anhydrous dicalcium phosphate, calcium metaphosphate, and a chemical blend of monoand dicalcium phosphate were of intermediate effectiveness, producing yield Increases of about 70 to 80% of that given by CSP. Granular calcium metaphosphate was the least effective source, being about 60% as effective as CSP in promoting yield increases. They concluded that, on calcareous soils, a highly water-soluble source of P, such as CSP, is likely to be more effective in broadcast applications for corn tlian .-ire most sJiglitJy solul)l(,' P sources. Tliey noted, liowever, that other characteristics of the fertllf/er may be of equai importance in determining their effectiveness. In growth chamber and field studies with maize, McLean ^ (1965) employed partially acidulated rock phosphate (with H3PO4) to study its effect on the yields and P content of German millet and alfalfa ( Medicago satlva L) . Growth gn the chamber Increased to a nuiximum at 72 kg P/ha and 20% acidulation on one group of soils and continued to increase with application rate and acidulation degree in another group. They did not obtain any appreciable difference with three methods of preparation of 20% acidulated material. Average field corn yield on the five above soils was highest with 20% acidulated material, resulting in marked economic advantage of this material.

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24 McLean and Logan (1970) evaluated several phosphates which differed in water solubility as sources of P for plants grown in soils with varying degrees of P retention. They reported that, with relatively low P retention, P content of maize seedlings increased in direct proportion to the P water solubility, but soils with high P retention resulted in content that decreased with increased water solubility of P. In experiments with maize, Meelu ^ (1977) found that all P sources at 60 kg P 20 s/ha were equally effective with evidence of luxury uptake of P from water-soluble P sources. All P fertilizers had a residual effect and soil test for P was significantly correlated with yield of successive crops. Infertile soils were used by Mortvedt and Terman (1978) to grow maize in three greenhouse pot experiments where the soils had received 0-800 mg P/pot as CSP, MAP, a 30:70% mixture of CSP and MAP or a 10:90% mixture of CSP and MAP. Responses were greatest for MAP at adequate P levels and occurred at rates much higher than normally recommended for field experiments. Pelletized Phosphate The main objective of coating granules of water-soluble phosphates is to reduce fixation of applied P by the soil, thereby increasing its availability for crop growth. Negative results have usually been obtained, however. Terman e^ (1970) reported no response of a first crop of flooded rice to P in S— coated CSP , but the P became available to a second crop after degradation of the coating. Allen and Mays (1971) found that

PAGE 41

25 insufficient P was released from S-coated DAP for early growth of forage sorghum ( Sorghum bicolor L.) and resulted in lower total yields than did uncoated DAP. Nicholaides et (1979) compared pelletized ordinary superphosphate (OSP) , uncoated CSP, or coated with S and sealant (SCSP) in a Rhodic Paleudult (a Red Bay, fine, sandy loam), previously uncultivated. They obtained the increase in corn grain yield for the first 28 kg P/ha and further response was linear at 200 kg/ha yield for each additional 28 kg/P applied. They found that field response was not significantly different either for P sources or for P placement. They observed no grain yield advantage to blending OSP and SCSP pellets either in the first or third year. Tlieir soil test values and car leaf P values showed linear responses to rates of applied P. Phosphate Placement Fertilizer is considered to be broadcast when applied over the entire soil surface. While most fertilizers are applied in this way (with subsequent -incorporation) broadcasting may also include topdressing on growing crops. Broadcast P, however, is generally applied prior to planting since the growing plant needs P early in its development. Acidulated P materials to be broadcast on acid to neutral soils generally do not need to be high in water-soluble P as discussed above. Field data showed that water solubility of broadcast P fertilizer on acid to neutral soils was not Important (Webb and Pesek, 1959). However, water solubility of P fertilizer broadcast on calcareous soils was found to be quite important (Webb ^ 1961) .

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26 Application of P is needed less frequently if higher rates of P are used. In a rotation experiment, Barber (1969) broadcast P fertilizer once every 4 years at rates of 98 and 196 kg P/ha over a 16-year period. Both rates were effective in maintaining yields through the fourth year following each application. He concluded that more flexibility in P application is possible without seriously affecting yield, provided that the P is plowed under or mixed deeply into the soil. Field experiments were conducted at three locations in Nebraska and one in Illinois by Cihacek ^ al. (1974) to compare alternative P application techniques for corn. These were chisel-broadcast, chisel placed (at 18to 20-cm depth), chisel-row band, and moldboard-broadcast. Results of 3 years of experiments showed that the moldboard incorporation of broadcast P was the most effective combination. It was concluded, however, that tillage effects were more important than placement of P. In field trials on an Oxisol in Brazil, P rate and placement were examined for maize grain yield (Yost, 1978). Their maximum yields were obtained where 560 kg P/ha were initially broadcast and where 140 kg P/ha were broadcast initially followed by consecutive band application of 35 kg P/ha for each crop. It is usually recommended that for row and band P applications, the P source should be largely in water-soluble form in order to stimulate growth. Webb and Pesek (1958) studied the effect of a range of water-soluble P content from 2 to 100% of the available

PAGE 43

27 P placed at 2.5 cm to the side and 4 cm below maize seed planted in 100by 100-cm hills. Their increase in yield with higher water-soluble P content was quite marked. In soils of Tanzania, 40 or 80 kg P/ha were applied by (a) broadcasting on the soil surface after sowing maize, (b) side dressing after sowing, and (c) drilling 2 to 3 cm below seeds in the planting furrow. When they compared unfertilized control grain yield of 2.5 t/ha to those with P placement methods (a), (b) , and (c) grain yields increased by 200, 700, and 900 kg/ha, respectively, at 40 kg P/ha. At the higher P rate, method (a) gave yields alike those found for 40 kg P/ha applied by method (b) or (c) . They studied interactions between applied N and P using 0, 40, 80, or 120 kg N/ha and 0, 30, 60, 90, or 120 kg P/ha. These maize yields Increased linearly with N rate and this effect was enhanced where 60 kg P/ha was applied. Leaf P content increased linearly with increased rates of P supplied alone or with N. (Uriyo et al., 1980). Bates (1971) summarized the response from selected treatments of 22 field trials in which normal tillage (plowing and disking) was practiced, and in which P and K were plowed down or banded beside and below the seed either as row or starter placement. He reported that, in only 2 out of 22 field experiments in Ontario, did maize yield increases result from starter fertilizer. In Australia, Rudd and Barrow (1973) found that when superphosphate was row-placed for wheat, it was about twice as effective as that applied broadcast at seeding. Prummel (1956)

PAGE 44

28 found similar results for several crops including maize, and small grains on P-deficient soil in the Netherlands. Welch et al. (1966) investigated the relative efficiency of broadcast versus banded P and reported that banded P for row crops can be more effective than broadcast P at lower rates of application. However, higliest yields were obtained with a combination of banded and broadcast P. This agreed with the findings of Barber (1958) for corn that banding alone on low P soils is inadequate and the supplementary broadcast P is needed to reach top yields. Barber (197‘^ib) introduced the concept of strip application of ^^^bilizer P as a compromise between broadcast and row placement. He found that surface placement of fertilizer in narrow strips before plowing was more effective than either banding or broadcastl)lowlng trentmontM almie. Thl.sjtrlp np|. 1 I cal Ion rcMulK'd In 8 Lo 10% of the plow layer being affected by fertilizer P after plowing. Little data are available to indicate the effectiveness of surface-applied fertilizer in continuous no-tillage systems of corn production. In one of the few studies with P fertilizers applied to the soil surface for corn production and not incorporated, .SIngli ct al. (1966) found lilghor I’ upt/iki* from aurfaco-a|)pl led I' than P incorporated into the soil. Surface application of P and K fertilizer to meadow crops has been more effective than incorporation of the fertilizer in the plow layer prior to establishment (Stanford £t ^l. , 1955). Broadcast applications of P and K fertilizer have also been effective on established meadow crops (Adams £t al. , 1967; Templeton £l. , 1966) .

PAGE 45

29 Belcher and Ragland (1972) concluded that if P was surface-applied in a no-till system, it was equal in effectiveness to P incorporated into the soil. Several workers have shown no-till corn yields to be equal to or higher than those obtained by conventional tillage (Meschler and Martens, 1975; Triplett and Van Doren, 1969). They stated that the P source used for surface application should be largely water-soluble. Fluid Fertilizers The term fluid fertilizers is usually used to include both fertilizer solutions and suspensions (Engelstad and Terman, 1980). These workers proposed that, for a valid comparison of fluid and solid fertilizer P, the P should be supplied in the same chemical compounds in both cases and be similarly placed so that they have comparable contact with soil and proximity to developing root systems . Lathwell e^ £l. (I960) summarized the results of a number of fiold experiments conducted to compare P sources in solution and solid form, involving maize, other field crops, and cotton ( Gossyplum hirsutum L.). They concluded that P in solution form is as satisfactory as in comparable solid sources, but is likely to be superior to those solid materials which contain a large proportion of water-insoluble P. They suggested that the price per unit of P applied in the field should be the main criterion in choosing between solid and solution forms of P. With suspension fertilizers, the P applied is usually quite insoluble. Finely ground phosphate rock for direct application

PAGE 46

30 can be applied in suspension form rather conveniently and avoids dust problems as well. In this way, the material can be applied in finely divided state as it should be for greatest effectiveness (Engelstad and Terman, 1980). Residual Phosphorus in Soils The use of optimal amounts of P for intensive cropping enables most soils to accumulate residual P (Johnson et al. 1969; Olsen nl. 1978). In drier areas wliere exLeiisIve cereal cropping is practLced, tlic soils often remain dericfent when annual '-•se has been minimal. In Saskatchewan, soil— available P was enhanced by the continued use of 20 kg P/ha or more with wheat in a 3-year rotation (Spratt and McCurdy, 1966). Both Read et al . (1977) and Bailey et al . (1977) , found that large amounts of P (100 to 400 kg P/ha) incorporated in the soil could support cropping on Chernozem soils for several years. Red soils of the warm and hot humid regions generally have inherently low levels of available P and high P-fixation capacities. De Datta £t £l. (1963) found that three latosol soils immobilized over 98% of the added fertilizer P. Woodruff and Kamprath (1965) found that the Ceorgeville soil (high in hydrated Al and Fe oxides) had a P-adsorption maximum of 720 kg P/ha, P as calculated from the Langmuir adsorption isotherm. They obtained optimum growth in a greenhouse study with 25% saturation of the P— adsorption maximum. Band applications of normal rates of phosphate fertilizers have been suggested on red soils for maximum effectiveness of

PAGE 47

3L the P. However, Barber (1965) pointed out that band applications of phosphate supply P to plants primarily during the first few weeks of growth. He maintained that for maximum economic yields soils should be high in nutrients throughout the root zone rather than In one spot. In a study of the residual effect of large applications of P on high P fixing (red) soils high in hydrated iron and aluminum oxides, Kamprath (1967) found a marked residual effect of P applied 7 to 9 years beforehand. They found that, even when P was added in the row, corn yields were as much as 50% higher when high rates had been applied 9 years before. This indicated that the P added initially was not irreversibly lost, but was available for plant growth in later years. The residual value of P in soils depends upon the nature of the compounds formed when phosphate fertilizers react with soil components. Several investigators (Ghani and Islam, 1946; Kaila, 1965; Lavery and McLean, 1961; Robertson ^ ^1. , 1966; Singh ^ a]^. , 1966; Volk and McLean, l963) have reported large recoveries of 1Â’ in tlie A1 and Fe form where i)hospliated soils were subjected to fractionation into the various extractable compounds . i According to Chang and Jackson (1958) , calcium and aluminum phosphates are likely to be formed soon after the application of phosphate fertilizers to mineral soils, and as time lapses, iron phosphate would be expected to form. In acid soils, the calcium ion activity may be of such low magnitude that calcium phosphate may not exist at all.

PAGE 48

32 Bowman et (1978) evaluated four P extraction methods — Olsen-P, Colwell-P, total exchangeable P, and resin-extractable P terms of total plant P uptake in a 3-year continuous greenhouse study of 23 calcareous and neutral soils high in P status. All methods were highly correlated with the total P taken up from the soils by 5 toSsuccessive greenhouse crops. They found that the Olsen-P method extracted an average of nearly 50^ that of the total plant P , while the Colwell procedure extracted nearly 80% of it. Resin-extractable P and total exchangeable P values approximated the total plant P uptake, and served as good biological measures of the total plant-available P in the soil.

PAGE 49

33 Maize Utilization of Phosphorus The levels of P availability in soils required for optimum crop production vary among the different crops. Maize is significantly more responsive than soybeans ( Glycine max L.) to fertilizer P application, as reported by de Mooy £t (1973). Another study reported for maize-soybean cropping system, found it was advantageous to apply the P fertilizer for the maize crop (Hanway and Olson, 1980). Similarly, wheat ( Triticum aestivum L.) responds to P at higher soil P levels than required for maximum yields for maize, presumably this is related to the fact that wheat makes most of its growth under colder soil conditions than maize (Olsen ^ al. , 1962). Some examples of the effects of certain P sources on the growth of maize have been given above. Terman e_t a_l. (1975) found that differences in nutrient absorption between maize hybrids was apparently influenced by genetic effects on growth rates and yield potentials. Herbage yields increased with increasing levels of applied Zn only where 167 ppm P was also supplied. Content of P in the tissue increased in response to the increase in rates of applied P. Maize grown in glasshouse experiments in soils from 68 locations in southeastern Nigeria responded in dry matter yields to P applied up to 56 kg P/ha (Enwezor, 1977). When available P levels were less than 34 kg P/ha, maize yields responded to applied P at 28 and 56 kg P/ha.

PAGE 50

A study by Creamer and Fox (1980) on the toxicity of banded urea or diammonium phosphate to maize showed both banded urea and diammonium phosphate were toxic to maize root growth. They 3f-tributed this to ammonia toxicity which was favored when the initial soil pH was increased and the soil moisture content accumulation had little effect on the root— toxicity symptoms. Research in Kenya In Kenya, a series of trials at Kitale showed that sowing date and cultivars were the most important factors affecting maize yields (Allan, 1974) . Plant density and weed control were also factors determining yields. It was found that early sowing increased yield of both poorly managed and optimally grown maize. In another study of the association between altitude, environmental variables, maize growth and yields in Kenya, Cooper (1979) found that the potential number of maize grains per embryonic primary ear was greatest at low altitude but the final number of grains per ear at harvest was greatest at high altitude. Growth stopped abruptly at 69, 83, and 96 days after tasselling at low. medium, .-md high alllliulo.M, ti'Mpocl I vc ly . Ylolda decreased with decreasing altitude and this was closely related to the mean thermal growth rate during the grain initiation period. Indole Acetic Acid in Maize Auxin action of indole acetic acid (lAA) in maize has been investigated by many workers. Edwards and Scott (1977) studied

PAGE 51

35 the effect of lAA on maize root segments in a citrate-phosphate buffer at pH 4 and pH 7. At neutrality, O.lyM of lAA promoted cell elongation only briefly whereas at pH 4 the rate was five times greater. They noted that elongation rate for root segments was much less than that for elongation rate of coleoptile segments when exposed to lAA at pH 6.8. Investigations by Davies ^ al. (1976) with resin beads containing lAA placed at 0.5, 2, or 5 mm from maize root tips showed that only 10% of the lAA was in the growing zone compared to that at the extreme root tip after 4 hours. They proposed that endogenous lAA could move to the growing zone of the root tip and might unilaterally inhibit growth if it was in the transport pool as exogenous lAA. Other studies by Naqvi (1976) used ^**C-2-lAA at 0.05 to 1.6 mg/liter on maize coleoptile segments and found that the highest efficiency for absorption and translocation of lAA was when the applied lAA was from 0.2 to 0.4 mg/liter. Research by Fernet and Filet (1976) with lAA applied to maize root caps showed that the LAA entered the root tip and moved basipetally inside the cap and they concluded that the polarity ol lAA ro.Hul.Lod In very hJ.ow LriiiiHport Irom Lho cap to the apex. The biosynthesis of LAA in aseptically cultured maize roots in media containing ^ **C-tryptophan or ^**C-1AA was demonstrated by Feldman (1980) . He reported that exogenously supplied LAA was rapidly and completely metabolized by root tissues and that the root apex was the main site for synthesis of lAA. This was

PAGE 52

36 shown by lAA continuing to be synthesized at the apex after the root cap and quiescent center were removed from the apex. The level of lAA of roots grown in this medium appeared to be precisely controlled by the roots. In maize cultivars resistant to low temperatures, Zaric (1978) found that the lAA content of the coleoptile was higher at 25°C than at 1°C but this effect was reversed with cultivars susceptible to low temperatures. They found that at the 3-leaf stage, lAA content was the same for the two sets of cultivars. Myoinositol esters of lAA were applied to cuts in maize endosperm and were shown to be transported at 400 times the rate of transport of lAA in studies by Nowacki and Bandurski (1980). They suggested that free lAA may be limiting for plant growtii since esLerll Ic.aLion of lAA occurred in the shoot and not in the endosperm. Other workers .have found that accumulation of lAA by maize coleoptile sections was pH-dependent (Edwards and Goldsmith, 1980). They noted that a short-term uptake of lAA in the sections was increased as the buffer pH was decreased. They observed that tissue cells at pH 5 retained mobile lAA at several times the concentration of the external lAA. A model for the effect of lAA on growth of maize coleoptiles was proposed by Darville ^ al. (1979) and included proton release by lAA, cell wall structure, and elongation growth. Maize roots were found to shDW growth inhibition to applied lAA unt,il the endogenous concentrratiop of lAA was reduced by

PAGE 53

37 exodiffusion so that both root growth and geotropism may interact with the balance of exogenous and endogenous lAA (Filet ^ al. , 1979). Use of growth-regulating chemicals on prolific and non-prolific maize plants were found by Sorrells ^ al. (1978) effect maize ear development. Tlicy used tlie compound N-l-napthylphthalmic acid (NPA) to inhibit auxin translocation. Since tlie use of NPA H 1 gii I f I can t l.y Increased tlii^ total ylcrld of non-|)ro I I f I c cnl.tlvars and increased the lower ear grain weight and ear number of all their cultivars, they suggested that lAA may interact with other hormones in a time— dependent mode for inhibition of lower ear development . Various cations have been found to alter the auxin activity of lAA. Evans et £l. (1980) reported that when lAA was present at concentrations that caused inhibition to the elongation of maize roots, the pH of the bathing medium increased sooner than that during a latent period for such inhibition of elongation. They concluded that the cell-wall pH was modified by the lAA and played a role in the control of root elongation. Under saline coiulltlons, I'aiuley (1.970) noted Ih.'il, wIkmi maize seeds were treated with 0 to 900 ppm in salt solutions of 1000, 2000, and 3000 (imhos/cm, there was a change in amino acid content. As salt concentration was increased, the level of aspartic acid and glutamine decreased. Presence of added lAA to the seeds resulted in an increase of tyrosine, tryptophan plus valine, alanine, cystine, and arginine in the maize plants. Goring -A* (1979) reported that lAA application and temporarily-reduced

PAGE 54

38 water potential reacted on the transmembrane potential of maize coleoptile within 15 minutes. This could be explained by lAA and water stress inducing activation of H"*" secretion by the plasmalemma. Work by Nowakowskl (1979) hlso showed tliat when maize was grown under conditions of osmbtic stress, lAA oxidase activity was reduced in the roots and shoots. Todor £t al. (1977) observed that, when Mg deficiency was induced in maize, addition of Mg alone or with lAA increased biomass accumulation and changed the plant chemical composition. Manganese restored the growthpromoting effect of lAA and decreased malate dehydrogenase activity of maize in an experiment performed by Kobyl'skaya et al. (1976). Phosphorus nutrition of maize was affected by a positive interaction between y-radiation and the addition of lAA, Zn, or Mn separately or together (Trlfu and' Osvath , 1978) . With oat ( Avena sativa L.) coleoptiles, Rubensteln ^ (1979) demonstrated that addition of Cd in the bathing medium stimulated lAA activity because protons were released from the cell-wall. Maize coleoptile segments under anaerobic conditions showed inhibition of cell enlargement, extrusion, and K"*" uptake which was attributed to imbalance of lAA activity (Rasi-Caldogno ejt al. , 1978). In another study, Nelles (1977) reported that maize coleoptiles treated for 16 hours with 10 lAA' increased in K permeability and decreased in Na permeability. Haschke and Luttge (1978) found that Avena coleoptile segments treated with lAA exhibited H"*" release by K"*" exchange with a concomitant synthesis of malic acid.

PAGE 55

39 Enzymatic synthesis of lAA from tryptophan was found to be decreased when maize plants were Zn— deficient and was restored rapidly after Zn application (Karakis, 1974). The binding of auxins to receptor sites of maize tissue was modified by a naturally-occurring compound 6, 7, dimothoxyl-2benzoxazoline (OMBOA) in a study by Venis and Watson (1978) . Other factors affecting the primary root requirement of maize for lAA were reported to be the lAA gradient from shoot to root (Martin ^ 1978), inhibition of lAA activity by red light (Vanderhoef and Briggs, 1978), and polar transport of lAA in vascular tissue of maize (Wangermann and Withers, 1978). Studies by Patel aT. (1978) were conducted using 2-day-old maize seedlings cultured in 10 ** Ppm of lAA for 24 hours. They reported that the riboxynucleic acid content was increased in elongating cells by the lAA treatment at different phases of elongation. Hall and Bandurski (1978) used ^'*C-1AA, ^H-IAA, or ^H-tryptophan to trace lAA movement from endosperm of maize to the shoot. Their results showed that lAA can move from endosperm to the shoot at a rate equivalent to that for simple diffusion. However, about 98Z of the transported lAA was converted to other compounds during the transport. They concluded that the rate of lAA and tryptophan— derived lAA transport of lAA and active lAA absorption by maize coleoptiles were both found to be temperature dependent and the lAA absorption of ^“^C-IAA from apically applied donor blocks was a linear function of time in experiments by Naqvi and Gordon (1978). To assist determination of lAA, improvement in

PAGE 56

40 assay procedures for lAA were developed by Mousdale et al. (1980) . Schurzmann and Hild (1980) found that externally applied lAA and abscisic acid (ABA) on vertical maize roots caused root curvature toward the donor agar block having the lAA. When the roots were horizontal, lAA applied on the upper side inhibited or delayed normal geotropic downward bending. The extent of retardation and inhibition of curvature depended on the lAA concentration in the donor block. Growth or curvature of roots was not affected by ABA in similar experiments. When root tips or coleoptile tips were placed on vertical roots, root curvature was observed. Lee (1980) sequentially treated stem segments of maize with phenolic substances and 2-^**C-lAA. The results suggested that the phenolics also affected the enzymatic oxidation of lAA in vivo in the same way as vitro. Phenolic pretreatment that affected formation of bound lAA was found to be ferulic acid, coumaric acid, or 4-methylumbelliferone. Compounds which were cofactors of lAA-oxidase increased the lAA incorporation while inhibitors of lAA-oxidase decreased it. Root segments of maize taken 2 mm long at 1 cm behind the root apex showed stimulation of elongation at pH 4. LAA decreased ®l*^^8^tion at pH 4 but stimulated it at pH 7 after a lag phase (Edwards and Scott, 1974). In another study by Jacobs and Ray (1976), it was found that auxin induced a decrease in the free space pH within 12 minutes for maize and 30 minutes for pea. There was a corresponding cell elongation at these times. Auxin analogs p-chlorophenoxyisobutyric

PAGE 57

41 3.nd phGny lac6 tic Gcid did not stinuilcitG clongntion or a dGcrease in pH in thG tissuG frcG spacG. THgsg findings ara consistant with tliG acid secretion theory of auxin action. Kticn 1 yptiiM Classification Although Eucalyptus forests almost everywhere in Australia look, alike, there are about 500 species, subspecies or varieties within the genus (Chippendale, 1973). The only textbook which deaJs comprehensively with eucalypt.us is that by W. F. Blakely, A Key to the Eucalypts, , which was first published in 1934 and later reprinted with some additions by R. D. Johnston in 1955 and with a nomenclature appendix by R. D. Johnston and Rosemary Marryatt in 1965. In the third edition of 1965, 676 species, sub-species, varieties and hybrids are recorded. Excluding the hybrids and doubtful species, and allowing for synonymy resulting from recent investigations, there are 444 separate valid taxa for which descriptions have been published (Chippendale, 1973). Pryor and Johnson (1971) drew up a classification incorporating the results of more recent study, drawing particularly upon information from the associated disciplines of genetics, ecology, and anatomy, as well as amplifying the study of morphology along traditional lines. In this classification, the genus Eucalyptus is divided into seven subgenera. In turn the subgenera are divided into sections, series, subseries, superspecies, species, and Hubspecios .

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42 Eucalyptus grandls Hill ex Maiden belongs to the subgenus Symphyomyrtus and the section Transversaria (Pryor and Johnson, 1971) . Eucalypts can be either trees or shrubs (Chippendale, 1973). The tallest species is mountain ash ( E. regnams ) from Victoria and Tasmania, recorded to about 98 m. In Western Australia, the tallest species is the karri ( E. diversicolor ) growing to about 76 m. On the other hand, some eucalypt species have a maximum height of 4.5 to 6 m, while some are shrubs only about 2 m high. E. grandis is a tall straight tree up to 46 m high. The bark is smooth and deciduous, white or subglaucos (Blakely, 1955). Its timber is red, light and durable. Tlie juvenile leaves are opposite for 3 to 4 pairs, shortly petiolate, oblong-lanceolate, thin, undulate, 3 to 6 by 1 to 2.5 cm. The intermediate leaves are alternate, petiolate, broadly lanceolate, slightly undulate, 12 to 18 by 5 to 6 cm. Mature leaves are alternate, petiolate, narrow-lanceolate, acuminate, undulate, 13 to 20 by 2 to 3.5 cm. Venation is moderately fine. Umbels are axillary, 3-to-lO-f lowered , or more. Peduncles are compressed, 10 to 12 mm long. Buds are pyriform, usually contracted in the middle, pedicellate, glaucous, 10x5 mm. Operculum is conical to shortly rostrate, shorter than the calyx-tube. The name Eucalyptus refers to the operculum, being derived from the Greek eu = well, and kalyptos ~ covered.

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43 The Eucalypts Range of Growing Conditions Eucalyptus is by far the most important genus of Australian forest trees. Its members dominate 95% of the Australian forest area and spread out over much of the remainder of the country (Hall ^ , 1970). A wide variety of hardwood timber is produced from these species; timbers which display a considerable range in characteristics such as color, weight, hardness, toughness, strength, elasticity, durability and fissibility. Because of this diversity of properties, eucalypt timbers have innumerable uses, many being pre-eminent for heavy structural purposes such as bridge building and harbor works. Apart from the major uses as timber and its derivatives, these trees yield valuable essential oils by foliage distillation, oils that are widely used in pharmacy, perfume manufacture, and industry (Hall ^ , 1970). Tannins are extracted in commercial quantities from the wood and bark of some species. Exceptionally hardy species such as some of the snow gums can withstand exposure to high winds, intense cold and heavy snowfalls above 5,000 to 6,000 feet in the Australian Alps and 3,000 feet in the highlands of Tasmania. At the other extreme, in the hot, parched desert and semi-desert regions of the inland, the eucalypts are restricted to watercourses and sheltered depressional areas where sufficient moisture is available to maintain existence during the normally long droughts. Many species exist on less than 250 mm of rain a year (Hall et al. , 1970) .

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Eucalypts have been able to adapt themselves to a wide range of conditions in both tropical summer rainfall and cool temperate winter-rainfall areas. They occupy both dry and wet sites, even swamps in places, exposed positions and sheltered congenial slopes and valleys, infertile sands, richer mellow loams and intractable clays (Hall £t £l. , 1970) . Most eucalypt species produce seed prolifically so that, if soil conditions are favorable for germination, an abundant crop of young seedlings is assured to restock whatever blank spaces there may be (Rule, 1967). Apart from these deaths due to overcrowding, bushfires, grazing animals, insects, and fungi take heavy toll of such regrowth right from the start, unless man comes to nature's aid. One reason why eucalypts have become so popular, for afforestation in other countries where the climate approximates to that of their native habitat, is that they are easy to raise from seed in forest nurseries. Australia relies largely on natural regeneration (seeding from parent trees) wherever possible Eucalypts as an Exotic Plant The story of the cultivation of tlie eucalypts and the early recognition of their economic possibilities commenced with the establishment of small plantation in southern Europe and North Africa about 100 years ago (Penfoid and Wiills, 1961). Since Uien the ease with which the eucalypts can be cultivated, their rapid growtli, and their adaptability, have led to their widespread

PAGE 61

45 introduction into many countries, especially in those which are poorly endowed with forest resources. Eucalyptus was introduced into California in 1853 (Penfold and Willis, 1961). Later seeds of many species were raised and distributed from 1886 to 1888. Plantations were soon after established in certain areas of California, Arizona, New Mexico, and Florida. Eucalypt plantations were established in Kenya at the beginning of the twentieth century. Eucalyptus grandis E. grandis comes from eastern Australia (FAO Forestry Development Paper, No. 19, 1974). It comes from areas with a rainfall of 900 to 1,270 mm, fairly well distributed throughout the year, but with a marked summer maximum, especially toward the north of its range. The timber of JE. grandis is lighter, softer and more fissile than that of most eucalyptus, with moderate strength and durability, prone to warping and other defects especially when sown from young or fast-grown trees (Streets, 1962). The timber quality of fast-grown hybrids between saligna and grandis would seem to need examination. Both species and the hybrid make good poles but need preservative treatment for telegraph and transmission poles . Only small areas of authentic saligna and E. grandis of Australian origin have been planted in savanna conditions (FAO Forestry Development Paper, No. 19, 1974). In trials in Zambia,

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46 it was found that sallgna was more drought sensitive than grandis or E. "grandis" from Africa. (The latter is of mixed origin and the name denotes the common form grown from African seed) . Site Quality As regards sites, much of the most successful planting of E. "grandis" in Kenya and Malawi has been done at high altitudes outside the savanna region, and in other countries in conditions of rainfall and moisture corresponding to moist high forest types. Phenomenal rates of production have been achieved under such favorable conditions. In Zimbabwe, formerly called Rhodesia, mean annual increments of 61 to 66 m^/ha have been recorded on the best soils in high rainfall areas (Barrett and Mullin, 1968). This is, however, exceptional. The tree requires good, deep permeable soils and cannot stand poor drainage or water-logging. At the same time, it cannot tolerate drought. A rainfall of 900 mm and upward, with a not too severe dry season, is suitable. In Zambia, where it is the major plantation species, it grows very well on the northern Plateau at elevations of 1,220 m, where it achieves a mean annual top— height increment of 5.1 m and a mean annual diameter increment of 4.2 cm in 2 to 4 years. E. "grandis" was tried in Congo under a rainfall of 1,200 bo 1,300 mm, but with a 4— month dry season. Though it started well, after the first 3 years, its condition deteriorated and this was attributed to shortage of water (Groulez, 1967).

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47 E. "grandis" in its various forms sets seed at an early age. It is relatively easy to handle in the nursery. Seed is sown direct into pots at the rate of 1 g/100 pots. Height growth is rapid and most seedlings reach a height of 30 cm in 10 weeks. In Zambia, smaller plants not more than 23 cm high are preferred. As for all eucalyptus planting, clean site preparation is desirable, and indeed is essential where moisture is likely to be insufficient at any time of the year. Clean weeding is necessary until the canopy has closed enough to suppress grass and invading weeds. The species is susceptible to termite attack and the usual precautions of applying insecticides at the time of planting have to be taken, especially on the drier sites where termite damage is always more severe. It also suffers from die-back on B-deficient soils and, in such cases, application of borate fertilizer may be necessary. Fertilizers There is very little information concerning the effect of fertilizers on the growth of eucalypts. From the scattered, rather empirical data that have been collected, it appears that tests with phosphatic fertilizers show little or no effect while nitrogenous fertilizers result, in some cases at least, in quite striking responses (Penfold and Willis, 1961). Using pot experiments with several species. Beadle (1953) found that added N and phosphate caused increased growth and the production of larger, softer leaves. This Indicates that the addition of nitrogenous and phosphatic fertilizers to plantations

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48 established for the production of leaf products, such as essential oils, may increase the overall yield by increasing the amount of leaf material produced per hectare. Container-Grown Seedlings Container seedlings and greenhouse production are no longer new concepts in many countries throughout the world. However, major research and development commitments and large investments in production facilities for mass production of container-grown seedlings were made only in the last decade in North America (Stein e^ ad.. , 1975). The use of container-grown stock varies among regions, because the relative advantage of this more labor-intensive system over the production of bare-root seedlings depends on shock tolerance of the species used, on climate, soil conditions, and on planting methods (Pritchett, 1979). The reasons or objectives for using container-grown seedlings vary among organizations, but they generally fit into one or more of the following broad categories (Stein £t al. , 1975). 1. Meet accelerated demands for nursery stock. Facilities for production of seedlings In containers can be expanded rapidly and seedlings can be produced quickly on more certain, flexible schedules than in bare-root nurseries. 2. Produce some species more readily. For a variety of reasons, certain species are difficult to produce in bare-root nurseries or are particularly sensitive to bare-root handling.

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49 3. Achieve greater production and planting efficiencies. Through use of container-grown seedlings, improvements appear possible in most phases of reforestation. This includes more efficient use and control of genetically improved seed, production of more uniform stock, better protection of seedlings, greater opportunities for mechanization, improved quality and speed of planting, and easier planting among residues or stock. 4. Extend planting seasons. Greater flexibility in production of seedlings and the protection that is provided by the container may permit planting at times when bare-root stock is not available or not properly conditioned. Lengthening the planting season may also permit use of a smaller, or more stable work force. 5. Improve survival and growth of out-planted seedlings. Achieving better survival and growth is a universal goal for everyone who tries new reforestation techniques." Types of containers Several types and sizes of containers are commonly used. These may be grouped Into three categories: tubes, blocks, and plugs. Tubes can be constructed of either biodegradable or non-degradable plastics, or of kraft or other paper. Tubes require filling with a soil mixture or other growth medium. Some control in the degradation rate of the material from which the tubes are constructed is important to the health of the seedling and for handling purposes (Pritchett, 1979).

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50 Blocks are similar in shape and size to tubes, but they have no outer wall and require no filling. The block is both the container and the planting medium, and seeds are sown directly in the block. The entire package is later transplanted into the soil. They are molded from bonded softwood pulp, polyurethane foam, peat, peatvermiculite mixtures, or similar materials in which nutrients may be incorporated. Blocks have given excellent results under many conditions, but, unless produced locally, freight cost can be prohibitive (Pritchett, 1979). Plugs consist of seedlings grown in soil-filled molds, but, unlike tubeor block-grown seedlings, they must be removed from their containers before outplanting. Since the growth medium is bound only by the seedling roots, the plug can be rather fragile and not easily planted by machines.

PAGE 67

MATERIAL AND METHODS Soil Properties The main coffee-producing areas of Kenya of which Ruiru and Kabete are representative, are located on closely similar soil types, named by Gethin Jones (1949) as the Kikuyu series. These soils are deep, porous and naturally well drained. They are latosols and are derived from a volcanic parent inaterial, _^ rtiary trachytic lava, by weathering in situ . They have a high pore space, a fairly high cation exchange capacity and a high clay content, yet the field texture is that of a friable loam (Pereira, 1957). The highly porous surface of the Kabete soil has n good naturn] crumb structure and it is resistant to erosion. The soil depth may exceed 20 feet on the main ridges and can ^ less feet on the flanks immediately above the river valleys (Gethin Jones, 1949). The black cotton soils are also derived from volcanic parent materials of the Tertiary period. The Mwea soil was sampled at the Mwea Plain and the Athi soil was sampled at the Athi Plain. These soils have developed wherever the drainage system was poor. Kabete soil is dominated by kaolinite and halloysite but Mwea and Athi soils are dominated by montmorillonite which subjects tliem to extensive swelling and water] ogglng during wet seasons and drying and cracking dnrin)Â’ dry seasons, Otlier soli properties are shown In u table. 51

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52 Soil Preparation One hundred kilograms of each soil sampled at two depths , 0to 15-cm and 15to 30-cm, were sent from Kenya. They were air-dired and ground to pass through a 10 mm sieve. Thirty nine 1000 — g samples of each soil were weighed into polyethylene bags and placed in plastic pots. A greenhouse experiment was conducted to determine the growth and composition of grandis when treated with lAA and three CSP sources at three rates. The CSP sources were: (i) reagent grade monobasic calcium phosphate powder, (ii) pelletized CSP, and (iii) pelletized CSP containing 100 ppm of lAA. The latter two CSP sources were supplied by the International Fertilizer Development Center (IFDC) , Muscel Shoals, Alabama. The supplier stated that the analyses of the materials indicated that the two materials were essentially the same in P 2 O 5 content. Both sources contained 15.7% water-soluble P, while source (ii) contained 19.4% citrate-soluble P, and source (iii) contained 19.9% citrate— soluble P. The CSP was applied to give 28, 56, and 112 kg P/ha and the lAA without CSP was applied to give 0.031, 0.062 and 0.124 kg lAA/ha, these lAA concentrations were equivalent to those supplied by the rates of pelletized CSP with lAA. The CSP treatments were added to the soils in the bags and mixed thoroughly. When lAA was used alone, 1000 mg were dissolved in alcohol in a liter flask and made to volume with distilled water to give 1000 ppm lAA. From this, a secondary dilution was prepared and used to give 0.031, 0.062 and 0.124 kg lAA/ha in triplicate pots of soil. Each such

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53 treatment was thoroughly mixed with the soil after each appropriate quantity of lAA was added from a dispenser. The soil in each pot was watered to about 75% of its water-holding capacity. The experiment was a completely randomized design. Eucalyptus Experiment After the moist soils had equilibrated with the fertilizer treatments for 4 days, six pelletized E. grandis seeds were planted in six holes (one in each hole) at about 10 mm depth in each pot and gently covered with loose soil. About 3 weeks after emergence, the seedlings were thinned to three plants in each pot. At 5 weeks after emergence, NH4NO3 was added to give 224 kg N/ha. Potassium and zinc sulfates were added at 10 weeks after emergence to give 224 kg K/ha and 44.8 kg Zn/ha. When the plants were about 3 months old, magnesium nitrate was added to give 112 kg Mg/ha. Due to rapid evaporation of water in the greenhouse, it was necessary to flood the pots regularly in order to maintain suitable moisture content for the plants. In the beginning of spring, the temperatures were usually from 27 C to 32 C during the day but were higher towards the end of the season, occasionally reaching about 46°C. Height measurement of each plant was taken at 2, 3, and 4 months. At the end of 4 months, the plant tops were harvested and stem thickness at the base was measured with a micrometer. The plants were air-dried for a few days and then transferred to a drying room at 60°C. After drying was completed, they were

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54 weighed and milled. Small quantities of leaves of eucalyptus from the top layers of Mwea and Kabete soils were ground separately. After the eucalyptus harvest, soil samples were taken from the pots, air-dried, and ground in preparation for analysis. Maize Experiment after Eucalyptus Maize cultivar 'Pioneer 3160' was planted in the soils after eucalyptus harvest without disturbing the soil. Five seeds were planted in each pot. Because the temperature in the greenhouse was almost always 30°C during the day, the soils in the pots were flooded periodically to ensure optimum moisture content for the plants. About a week after emergence, they were thinned to three plants per pot. Three weeks after emergence, NH4NO3 was added to give 224 kg N/ha and at 4 weeks after emergence (NH 4 ) 2 S 04 was applied to give 224 kg N/ha. I Height measurements were taken at 2, 4, and 6 weeks after emergence. The plants were harvested 6 weeks after emergence, air-dried for 2 days and then transferred to a drying room. After they were completely dry, they were weighed, and ground. After the maize harvest, soil samples were taken from the pots, air-dried, and then ground in preparation for analysis. Maize Experiment with Two Soils Athi and Kabete soils from 0— to 15— cm depths , with fresh CSP and lAA treatments at the same rates as had been used for eucalyptus, were planted with the same above variety of maize \

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55 in a separate experiment in the greenhouse. Watering and the temperatures were the same as for the succession experiment. These plants received the same amounts of NH4NO3 and (NH4)2S04 as those in the succession experiment at the same time. Height measurements were taken at 2, 4, and 6 weeks after emergence and were harvested after the last height measurement. A single fourth leaf from each pot was put in a separate bag. These were all air— dried for 2 days and then transferred to a drying room. After they were completely dry, they were weighed and ground. The leaf samples which had been put in separate bags were also ground separately. Weights of these latter samples were included with the main weight of the harvested tops. After the maize harvest, soil samples were taken from the pots, air-dried, and then ground in prcjiaration for analysis. The maize roots were separated from tlie soils and waslicd free of soil before drying at about 70°C in an oven for several days. When dry, the roots were weighed and then ground with a small mill. Analytical Methods Particle-size analyses on soil samples less than 2 mm were done according to the pipet method as outlined in the Soil Survey Investigations Report No. 1 (1972). Organic carbon in the soils was determined according to the method of Walkley (1946). Walkley and Black (1934) obtained 60 to 86% recovery of C, for which their multiplying factor was

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56 1.30. Peech et al . (1947) reported a similar multiplying factor of 1.33. In view of their report, a multiplying factor of 1.33 was used in the present study. Nitrogen in eucalyptus leaves from the top samples (0 to 15 cm) of Mwea and Kabete soils was determined according to the semimicro-Kjeldahl method as outlined in Black (1965). Soil pH was determined by glass electrode pH meter using ^ 1-2.5 soil to water ratio, following the procedure outlined by Black (1965) . Reagents for P Determination Double Acid (DA) reagent . The DA reagent is 0.05 N hydrochloric acid in 0.025 ^ sulfuric acid. This reagent was prepared by pouring about 15 liters of deionized water into a 20-liter bottle and adding 14 ml of concentrated sulfuric acid and 83 ml of concentrated hydrochloric acid. The volume was made to 20 liters and thoroughly mixed. Reagent A . Weigh 12 g ammonium molybdate and dissolve in about 400 ml of distilled water. Add 0.2908 g of antimony potassium tartrate and dissolve in 100 ml of distilled water. Both of these dissolved reagents are added to 1000 ml of 5 N H2SO4 (148 ml concentrated H2SO4 per liter), mixed thoroughly and made to 2 liters. Reagent A was stored in pyrex glass bottle in a dark and cool compartment. Reagent B . Dissolve 1.056 g of ascorbic acid in 200 ml of reagent A and mix. This reagent was prepared as required, as it does not keep for more than 24 hours (Murphy and Riley, 1962).

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57 Sodium bicarbonate (SB) reagent . This reagent is 0.5 M NaHCOs solution at pH 8.5. The pH of 0.5 M NaHCOa was adjusted with 5 M NaOH for 10 liters of the solution which was prepared. Tlie solution was stored in a polyetliylcne container. Carbon black . Darco activated charcoal was used. P standards . Exactly 0.2195 g of oven-dry KH 2 PO 4 was dissolved in 500 ml of distilled water and 5 ml of concentrated sulfuric acid were added as a preservative and diluted to 1000 ml in a volumetric flask. This standard was 50 ppm P and was used as needed. A secondary P standard was prepared by pipetting 25 ml of the primary P standard into a 250-ml volumetric flask and was made to volume with DA reagent. This standard contained 5 ppm P and was kept in a refrigerator. Soil Extraction In order to use an appropriate DA/soil ratio in the extraction, pH of blank (DA reagent only) was compared with pH of various solution/soil ratios. The solution/soil ratios examined were 10:1, 7:1, and 4:1 employing 50, 35, or 20 ml of DA reagent/5 g soil respectively. The pH of the supernatant after shaking for 30 minutes was measured. The pH of the 10:1 ratio was the closest to that of the reagent. A 5.0-g sample of each soil sample was weighed into 125-ml extracting bottles and 50 ml of DA reagent were added with an automatic pipette. The bottles were placed in a rack on a mechanical, reciprocating shaker and shaken for 30 minutes.

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58 Sartain at al . (1976) , working with ten mineral and organic soils from Florida, obtained a curvilinear increase in the quantity of P extracted by DA reagent and 0.03 N NH 4 F in 0.05 N HCl with a occurring between 15 and 20 minutes. A longer extracting (shaking) time was chosen for the present study because the soils had a higher clay content. The soils were filtered through Whatman No. 2 filter paper. The filtered extracted solutions were used for elemental analysis. The 0.5 M NaHCOs method of Olsen ^ al. (1954) was used with a slight modification. A 2.5-g portion of soil was shaken with 50 ml of the solution for 30 minutes. Activated charcoal (Darco) to remove dissolved organic matter was added and the extract shaken vigorously before filtering through Whatman No. 2 paper. These filtrates were clear. Extraction of Plant Tissue Eucalyptus . A 0.50-g sample of ground eucalyptus tops (or leaves) was weighed into crucibles and heated in a muffle furnace for 2 hours at 350°C. Heating was continued at bbO^C for 4 hours. The crucibles were allowed to cool. A few drops of distilled water were added to moisten the ash and 5 ml of 40% HCl (2 parts concentrated HCl to 3 parts distilled water) were added and the solution was gently evaporated to dryness on a hot plate in a fume cupboard. The crucibles were washed with 50 ml of ^ HCl (a little at a time) , filtering the washings through Whatman No. 2 paper. The filtrate was collected in bottles and used for elemental analysis.

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59 Maize . A 0.50-g sample of dry maize tops was weighed and heated in a muffle furnace at 350 °C for 2 hours. The temperature was raised to 550°C and heating continued for 4 hours. After cooling, the ashed samples were moistened and 5 ml of 40% HCl were added and evaporated to dryness on a hot plate. Due to the presence of black ash, these samples were reheated in the muffle furnace at 350°C for an hour and then at 550°C for 4 hours. After cooling, the ash was moistened with a few drops of distilled water and 5 ml of concentrated HNO 3 were added and evaporated to dryness on hot plates. These residues were washed with 50 ml of ^ HCl, collecting the filtrate through Whatman No. 2 paper and retained in polyethylene bottles. A 0.05-g sample of the fourth maize leaves from Athi and Kabete soils (0to 15-cm depths) were weighed and ashed as the maized tops had been done. A 0.50-g sample of maize roots from these same soils were ashed as above and the ash dissolved in 50 ml of 1 ^ HCl. P Determination Zero, 1, 2, 3, 4, and 5 ml of the 5 ppm P standard were pipetted into 50-ml volumetric flasks. They were filled half-way with distilled water. A few drops of 2,4-dinitrophenol were added followed by 2 ^ NaOH until a yellow color appeared and ^ HCl was added drop by drop until the yellow color just disappeared. Then 8 ml of reagent B were added from an automatic dispenser, made to volume with distilled water, and

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60 niLxed well. Tlic color was allowed Lo develop for 20 niliuites before being read on a bauscli & Lomb Spectronlc 21 at 882 nm. The P concentrations in the standards were 0, 0.10, 0.20, 0.30, 0.40 and 0.50 ppm. The zero P standard was used to set the instrument . reading at 0.000 P concentration and 0.50 ppm P standard was used to set the maximum reading 0.500. Suitable aliquots of the soil extracts were taken. A 1-ml aliquot of the plant extracts was taken for P analysis. Color was developed in the same way as for the standards using the same instrument at 882 nm and the calibrated readings were taken from the instrument. Calcium, Mg, Cu, Fe, Mn and Zn were determined by atomic absorption spectrophotometry using a Perkin Elmer 5100 instrument and K was determined by emission flame photometry at 769 nm. Statistical Analysis All the experiments were completely randomized designs. The computer used for the statistical analysis is an Amdahl V-6-II and IBM 3033 with an OS/MVS Release 3.8 and J 2S2/NJE Release 3. The analysis was done using an in-house program at the Department of Statistics, University of Florida. The analysis was obtained by converting the factors lAA rate, P source, and P rate to a single factor labeled as treatment, with 13 levels. Single degree of freedom comparisons were then defined based on the original 3 factors. The contrast used and the corresponding treatment are given in the following table.

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Treatment comparison Abbreviation Linear effect, lAA alone 1 1AA,L Quadratic effect, lAA alone 2 1AA,Q CSP Powder vs CSP Pellet (Form) 3 CSP form Linear effect, CSP alone (Rate , Linear ) 4 CSP,L Quadratic effect, CSP alone (Rate, quadratic) 5 CSP,Q Component Form x Rate interaction 6 Form X rate,L Component Form x Rate interaction 7 Form X rate.Q Linear effect, lAA+CSP pellet 8 CSP*1AA,L Quadratic effect, lAA+CSP pellet 9 CSP*1AA,Q lAA alone vs CSP alone 10 lAA vs CSP alone lAA+CSP pellet vs lAA alone, CSP alone 11 CSP*1AA vs CSP+IAA Control (No lAA, No CSP) vs others 12 Control vs others In subsequent tables, the rates were given as r2, r3, . . . . r7. which stand for the rates of lAA and CSP which were applied, in kg/ha. Tlius , for lAA, terms r2, r3, and r4 represent 0*031, 0*062, and 0*124 kg lAA/ha, respectively. For CSP, r5, r6, and r7 represent 28, 56, and 112 kg P/ha, respectively. The abbreviations lAA, CSP, DA, and SB are used to represent indole acetic acid, concentrated superphosphate, double acid, and sodium bicarbonate, respectively. Phosphorus extracted by DA and SB is termed DA— P and SB— P, respectively.

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RESULTS AND DISCUSSION Eucalyptus Experiment Soils Although the soils used in the studies were very similar in pH, Kabete soil had a much higher organic matter content than Athi or Mwea. On the other hand, Mwea soil had a much greater P extractable by double acid (DA-P), being 550 ppm, than either Athi or Kabete each of which had less than 10 ppm P (Table 1). Athi and Mwea soils have more than 50% clay which is mainly montmorillonite . This property made them difficult to water suitably because of the ease of swelling when wet which inhibits water infiltration. Both depths of the Kabete soil have an average of 50% silt and an average of 17% sand. This property, besides its kaolinitic nature, facilitated watering and aeration. Moreover the high percentage of organic matter particularly in the 0to 15-cm layer of Kabete soil enhanced good crumb structure, a desirable characteristic. Growth Factors During the early growth of eucalypt seedlings, there was widespread occurrence of purplish colors on the stems on most plants except those growing on Mwea soil which was very high in P as determined by double acid. The purple (or brown) color was believed to be due to P deficiency. In the later stages of growth (that is about 2 to 3 months), the lower leaves started to lose the green color, becoming yellow and finally red. Addition of magnesium nitrate apparently rectified this problem. 62

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63 Table 1. Some properties of soils from Kenya. Soil Athi , cm Mwea,cm Kabete ,cm Analysis 0-15 15-30 0-15 15-30 0-15 15-30 pH 6.5 6.8 6.3 6.3 6.4 6.4 (1:2-5, soil to water) %C 1.76 1.65 1.69 1.58 7.09 3.34 % sand 12.1 11.6 7.6 7.6 19.7 14.7 % silt 32.4 30.5 25.6 24.4 45.0 55.1 % clay 55.5 58.0 66.8 68.0 35.4 30.2 ppm IÂ’ by DA method 4.5 5.5 550 550 7.0 1.0

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64 Significant responses to treatments, soils, soil depths, and their interaction with treatment comparisons were obtained (Table 2) . At 2 months since emergence, height showed a significant response to CSP form, the means being 18*8 and 16 "9 cm, for the powder and pellet forms, respectively (Table 3). This significant difference is substantial on the Kabete soil for which the height for the three rates of CSP powder are approximately double those of the corresponding rates of CSP pellet. There was a linear response of height to CSP form and a quadratic response to P form and rate at 2 months since emergence (Table 2) . The height was less where lAA alone was used compared to that for CSP alone but this effect differed between soils and depths. Growth increase for CSP was 15'9, 7-6, and 6*3 cm for Athi, Mwea, and Kabete soils respectively (Table 4) . Depth of soil also influenced the height differences between lAA and CSP treatments. Table 5, and the difference in height was 8*8 cm for plants on soil from 0 to 15-cm depth compared to an ll*2-cm difference at the 15 to 30-cm depth. A comparison of CSP+IAA and CSP with lAA (i.e. CSP'IAA) shows that the height was significantly less for CSP+IAA for Athi and Mwea soils (Table 6) . Depth influenced this difference in that the height difference was greater for the 15 to 30-cm depth (5*9 cm) than for the 0 to 15-cm depth (3*3 cm). Table 7. Growth on control treatments was less than on the other treatments (comparison 12) and these differences were influenced by both soils and soil depths. Tables 8 and 9. For Athi and Mwea soils, the height was significantly greater for the other treatments than for the control. However, the

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65 Table 2. Means and significant height responses for Eucalyptus grandis grown on three soils treated with lAA and CSP. Factor Rate Height, months 2 3 4 Treatment comparisons No. Type Height, months 2 3 4 kg/ha cm sum of squares Treatment ** ** kk Control 12.4 25.5 51.7 1 ' lAA r2 8.3 20.7 53.2 1 1AA,L lAA r3 7.7 21.0 49.7 2 1AA,Q lAA r4 7.6 21.2 50.5 3 CSP form k-k CSP powder r5 16.5 32.1 58.1 4 CSP,L kk CSP powder r6 20.0 35.0 62.2 5 CSP,Q CSP powder r7 19.8 33.5 59.9 6 Form X rate,L CSP pellet r5 16.5 31.1 60.1 7 Form X rate,Q kk CSP pellet r6 15.9 30.8 62.3 8 CSP'1AA,L „ CSP pellet r7 18.3 33.1 61.8 9 CSP-1AA,Q CSP-IAA r2+r5 17.7 33.0 63.2 10 lAA vs CSP kk kk kk CSP'IAA r3+r6 17.1 31.1 57.3 11 CSP-IAA vs CSP+IAA** kk CSP-IAA r4+r7 17.1 32.9 61.0 12 Control vs others kk kk k Soils kk kk kk Athi 15.9 26.9 52.2 Mwea 18.7 32.8 60.4 Kabete 10.3 28.3 60.8 Soils X treatments 1 as above kk kk 2 3 4 kk kk 5 6 1 kk 8 9 10 kk kk kk 11 kk kk kk 12 kk kk kk

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66 Table 2-continued. Height, months Treatment comparisons Factor Rate 2 3 4 No. Type Height, months 2 3 4 Depths Depths X kg/ha treatments cm as above sum of squares ** ** ** 1 2 3 4 5 6 7 ** 8 9 10 ** ** 11 ** ** 12 * and denote significance at the 0.05 and 0.01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).

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67 Table 3. Soil x found treatment means for for eucalypt height CSP forms x rate at 2 months. quadratic effects P P Soil form rate Athi Mwea Kabete Mean kg /ha Means*, cm CSP powder 28 14.4 20.4 14.6 16.5 56 22.4 20.7 17.0 20.0 112 20.6 20.2 18.7 19.8 CSP pellet 28 22.1 19.7 7.9 16.2 56 19.5 20.2 7.9 15.9 112 23.1 21.1 10.7 18.3 Difference above 2.3 is significant at the 0.05 level except for mean values.

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68 Table 4. Interaction of soils for lAA and CSP comparison for eucalypt height at three times. * Treatment Athi Soils Mwea Kabete Significant difference 0.05 level Mean ( cm) 2 months 1.8 CSP alone 20.3 20.4 12.8 lAA alone 4.4 12.8 6.5 Difference 15.9 7.6 6.3 3 months 2.4 CSP alone 32.7 34.8 30.4 lAA alone 11.5 26.8 24.0 Difference 21.2 8.0 6.4 4 months 4.9 CSP alone 58.7 62.3 61.7 lAA alone 35.7 55.3 61.3 Difference 23.0 7.0 0.4 :k lAA alone is the mean of treatments 2, 3, and 4 and CSP alone is the mean of treatments 5 through 10.

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69 Table 5. Mean effect of soil depths on eucalypt height in response to lAA and CSP alone. ^ Soil depth, cm Treatment 0-15 15-30 Mean , cm 2 months CSP alone 18.6 17.2 lAA alone 9.8 6.0 Difference 8.8 11.2 3 months CSP alone 32.9 32.3 lAA alone 24.4 17.6 Difference 8.5 14.7 4 months CSP alone 60.1 61.4 lAA alone 53.9 48.4 Difference 6.2 13.0 * as in Table 4. Significant difference 0.05 level 1.7 2.4 4.9

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70 Table 6. Interaction of soils on comparison of mean eucalypt height for CSP with lAA (CSP-IAA) and CSP+IAA. Source Soils Significant mean Athi Mwea Kabete difference 0.05 level Mean , cm 2 months 1.8 CSP-IAA 22.1 21.3 9.8 CSP+IAA 12.4 16.6 9.7 Difference 9.7 4.7 0.1 3 months 2.4 CSPÂ’IAA 35.4 31.6 28.4 CSP+IAA 22.1 30.8 27.2 Difference 13.3 0.8 1.2 4 months 4.9 CSP-IAA 60.9 61.9 58.7 CSP+IAA 47.7 58.8 61.4 Difference 13.2 3.1 2.7

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71 Table 7 . Interaction of soil depths on comparison of mean eucalypt height for CSP'IAA and CSP + lAA. Source mean Soil 0-15 depth, cm 15-30 Significant difference CSP-IAA 17.5 Mean , cm 2 months 17.5 0.05 level 1.8 CSP+IAA 14.2 11.6 Difference 3.3 5.9 3 months 3.4 CSP-IAA 31.1 33.4 CSP+IAA 28.7 25.0 Difference 2.4 8.4 4 months 6.9 CSP-IAA 59.6 60.9 CSP+laa 57.0 54.9 Difference 2.6 6.0

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72 Table 8. Mean effect of soils on eucalypt height, comparing controls with the other treatments. Treatment Athi Soils Mwea Kabete Significant difference 0.05 level Mean , cm 2 months 1.8 Other treatments 16.7 27.8 10.2 Control 5.5 18.9 12.6 Difference 11.2 8.9 2.4 3 months 2.4 Other treatments 19.2 32.8 28.0 Control 13.1 32.1 31.1 Difference 6.1 0.7 3.1 4 months 8.5 Other treatments 45.2 60.4 52.6 Control 36.8 59.7 58.7 Difference 8.4 0.7 6.1

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73 Table 9. Mean effect of soil depth in eucalypt height on control compared to other treatments. Treatment Soil depth, cm 0-15 15-30 Significant difference Mean, cm 2 months Other treatments 15.9 14.1 Control 14.4 10.3 Difference 1.5 3.8 3 months Other treatments 30.4 28.7 Control 28.5 22.4 Difference 1.9 6.3 4 months Other treatments 58.9 58.0 Control 57.6 45.8 0.05 level 1.7 3.4 6.9 Difference 1.3 12.2

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74 opposite effect was observed in the Kabete soil, in which height of the plants on the controls was significantly greater than for the other treatments. This is really unexpected and is probably due to some other cause such as a more favorable property of Kabete soil (a latosol) compared to the black cotton soils (vertisol) , such as higher organic matter and good structure which facilitate water infiltration and aeration. Considering the depths, there was no significant difference in height response to either the control or the other treatments for the 0 to 15-cm depth but the height was significantly greater for the other treatments than for the control treatment in the 15 to 30-cm depth (Table 9) . At 3 months, the height was less where lAA alone was used compared to that for CSP alone. Growth increase for CSP was 21-2, 8*0, and 6*4 cm for Athi, Mwea, and Kabete soils respectively (Table 4). The differences were significant but alike those at 2 months as presented above. As for the previous month, depth of soil also influenced the height differences between lAA and CSP treatments. Table 5, and the difference in height was 8*5 cm for plants on soil from 0 to 15-cm depth compared to 14*7-cm difference at the 15 to 30-cm depth. The height was significantly less for CSP+IAA treatment than for CSP-IAA for Athi soil but no significant differences between these treatments were found for the other soils (Table 6). The influence of depth on these treatments, CSP+IAA and CSP'IAA, is that height was significantly greater for CSP'IAA treatment for soil at the 15 to 30 cm depth (Table 7) . The height

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75 difference for the 0 to 15 cm depth was 2' 4 (which is not significant) and, for the 15 to 30 cm depth, it was 8-4 cm. Growth on control treatment of the Athl soil was significantly less than on the other treatments but greater for Kabete soil. Table 8. The influence of the 15 to 30-cm depth on this was significant. Table 9, but the 0 to 15-cm depth had no significant effect on the controls compared to the other treatments. At 4 months, there was no significant difference in height between lAA alone and CSP alone on Kabete soil. In fact the difference that existed before narrowed after 2 months and disappeared at 4 months. However, the plants treated with CSP alone on the Athi and Mwea soils still had significantly greater height than those with lAA alone. These differences in height were 23 and 7 cm for Athi and Mwea soil respectively. Considering the whole growing period for this study, the height difference between the plants treated with CSP alone and those treated with lAA alone increased with time while that on Kabete soil narrowed and disappeared at 4 months as already stated above. The CSP alone had a significantly more favorable effect on height at both soil depths than lAA alone, as was the case previously (Table 5). Like the previous month the height was significantly greater for CSP*1AA treatment than for CSP-IAA on the Athi soil (Table 6). But unlike in the previous months, depth had no significant difference in its influence on these treatments (Table 7) . Growth on control treatment of the Athi soil was less than on the other

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76 treatments, though not significantly different. There was no difference in height for this comparison on the Mwea soil (being only 0‘7 cm). There was also no significant difference between the control and the other treatments in their effect on height of the plants on Kabete soil (Table 8). However, as was noted above, the plants on the control treatment had greater height on this soil than those on other treatments. Wherever this occurred, the probable cause is depression in growth caused by lAA which somehow cancelled the expected favorable effect of CSP. The height response of the plants was significantly less for the control than for the other treatments for plants grown on the 15-30 cm depth. The 0-15 cm depth had no influence on these treatment comparisons. As shown on Table 10, CSP had a significant linear effect on tops P. However, this effect is not clearly presented by Table 11 in which a quadratic effect is suggested by the data for both CSP forms and each of the three soils. There was a significant response of tops P to the lower P rates (28 and 56 kg P/ha) for both CSP powder and CSP pellet (Table 11) . At these rates response in tops P was significantly greater for the pellet than the powder form of CSP. Response in tops P was greatest in the Athi soil and least in the Mwea soil, although the latter was much higher than the other two in DA-P. Stem diameter responded significantly to the form of CSP, soils, depths, and interactions. In all the soils, CSP treatments

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77 Table 10. Means and significant stem diameter, weight P of Eucalyptus grandis grown on three soils lAA and CSP. of tops, and tops treated with Factor Rate Stem Tops Tops Treatment comparisons diam. weight P No. Type Diam. Weight Tops P kg /ha mm 8 % Sum of sciuares TrenLini'iiLH A AA A AA Control 5.0 17.6 0.072 lAA r2 4.3 13.7 0.088 1 1AA,L lAA r3 4.3 13.3 0.087 2 1AA,Q lAA r4 4.4 14.3 0.081 3 CSP form AA CSP Dowder r5 5.7 23.8 0.098 4 CSP,L AA CSP powder r6 5.8 24.0 0.136 5 CSP,Q AA CSP powder r7 5.5 23.6 0.187 6 Form X rate,L * CSP pellet r5 5.8 23.7 0.114 7 Form X rate,Q CSP pellet r6 5.4 22.1 0.159 8 CSP-IAA, L AA CSP pellet r7 5.7 25.0 0.189 9 CSP-IAA, Q CSPlAA r2+r5 5.7 22.8 0. 1]2 10 lAA vs CSP VcA AA A A CSPlAA i'3+r6 5.() 21.7 0.143 11 CSP-IAA vs CSP+IAA** ** •k* CSP-IAA r4+r7 5.6 22.4 0.190 12 Control vs others ** A A Soils 'k'k AA Athi 4.8 17.5 0.130 Mwea 5.5 21.5 0.116 Kabete 5.5 22.9 0.137 Soil X treatments 1 as above AA AA AA 2 3 A 4 5 6 7 8 9 10 11 12 ** ** ** **

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78 Table 10-continued . Factor Rate Stem Tops diam. weight Tops Treatment comparisons P No. Type Diam. Weight TopsP kg/ha mm g % Sum of squares Depths Depths X treatment as above 1 2 3 4 5 6 7 8 y 10 11 12 •k-k kk kk kk k k k k kk k kk kk k kk and denote significance at the 0.05 and 0.01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).

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79 Table 11. Interactions of P to CSP rates. soils with response of eucalypt tops P rate, kg/ha Soils 28 56 112 1 ^ 63^11 ^ to CSP Powder Athi 0.099 0.138 0.211 Mwea 0.087 0.127 0.152 Kabete 0.107 0.144 0.197 Mean 0.098 0.136 0.187 CSP pellet Athi 0.104 0.184 0.214 Mwea 0.103 0.136 0.171 Kabete 0.135 0.158 0.184 Mean 0.114 0.159 0.190

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80 caused significantly greater stem growth than the lAA treatment as shown in Table 12. The greatest difference in stem diameter between these two treatments was 2" 6 mm for the plants on the Athi soil although there was no significant difference in stem diameter among the soils treated with CSP. Stem diameter was significantly greater in the CSP-treated soils for the 15to 30-cm depth than in the same depth of soils treated with lAA (Table 13) . There was no significant interaction for the 0to 15-cm depth. Stem diameter was significantly less for the CSP+IAA treatment than for CSPÂ’IAA. This interaction was with the Athi soil. There were no significant interactions of Mwea and Kabete soils with CSP'IAA and CSP+IAA treatments with regard to stem diameter (Table 14) . Soil depths did not significantly interact with these treatments to show any significant differences in the stem diameter (Table 15) . Growth in stem diameter was significantly less for the control than for the other treatments on the Athi soil but had no difference on the other two soils. In fact the plants on control Kabete soil did slightly better than the treated ones (Table 16) . From data which were not tabulated, it was observed that both Athi and Mwea soils had tops weight which decreased with rate of CSP -LAA but which increased for Kabete soil. These effects were significant for Mwea and Kabete soils. CSP treatment caused significant increases in tops weight for all the soils compared with lAA (Table 12) . This effect of CSP is further shown in Table 13 in which this treatment had the same contribution in

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8 ] Table 12. Interactions for soils with response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP and lAA treatments Treatment Athi Soils Mwea Kabete Significant difference Mean values 0.05 level Stem diameter 9 rnm 0.47 CSP 5.7 00 5.7 lAA 3.1 5.0 5.1 Difference 2.6 0.8 0.6 Tops weight, g 3.1 CSP 22.7 23.1 25.3 lAA 5.4 16.9 18.9 Difference 17.3 6.2 6.4 Tops P, % 0.019 CSP 0.158 0.129 0.154 lAA 0.065 0.083 0.105 Difference 0.093 0.046 0.049

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82 Table 13. Interactions for soil depths on response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP and lAA treatments. Treatment Soil depth, 0-15 cm 15-30 Significant difference Mean values Stem diameter, mm 0.05 level 1.2 CSP 5.8 5.7 lAA 4.7 4.0 Difference 1.1 1.7 Tops weight. 2.6 CSP 24.4 23.0 lAA 15.1 12.4 Difference 9.3 10.6 CSP Tops P, % 0.152 0.159 0.015 LAA 0.099 0.072 Difference 0.053 0.087

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83 Table 14. Interactions of soils with response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSP, lAA and CSP plus lAA treatments. Treatment Athi Soils Mwea Kabete Significant difference Means 0.05 level Stem diameter. mm 0.47 CSP-IAA 5.7 5.7 5.5 CSP+IAA 4.4 5.4 5.4 Difference 1.3 0.3 0.1 Tops weight. 3.1 CSP-IAA 22.6 22.8 21.6 CSP+IAA 14.1 20.0 22.1 Difference 8.5 2.8 0.5 Tops P, % 0.019 CSP-IAA 0.157 0.135 0.153 CSP+IAA 0.112 0.106 0.150 Difference 0.045 0.029 0.003

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84 Table 15. Interactions for soil depths on response of eucalypt stem diameter, tops weight, and tops P for comparison of mean CSPÂ’IAA and CSP plus lAA treatments. Treatment Soil depths 0-15 15-30 Significant difference Means 0.05 level Stem diameter, mm 1.2 CSP'IAA 5.6 5.7 CSP+IAA 5.3 4.8 Difference 0.3 0.9 Tops weight, g 2.6 CSP-IAA 21.2 23.4 CSP+IAA 19.8 17.7 Difference 1.4 5.7 Tops P 7 2 ^ 0.015 CSP-IAA 0.161 0.153 CSP+IAA 0.125 0.116 Difference 0.036 0.037

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85 Table 16. Interaction of soils with response of eucalypt stem diameter, weight of tops, and tops P for comparison of control with other treatments. Treatment Athi Soils Mwea Kabete Significant difference Means Stem diameter. mm 0.05 level 0.47 Others 5.0 5.5 5.5 Control 3.5 5.5 5.9 Difference 1.5 0.0 0.4 Others 18.4 Tops weight, 21.5 22.8 3.1 Control 7.1 21.6 24.0 Difference 11.3 0.1 1.2 Others 0.136 Tops P, % 0.119 0.142 0.019 Control 0.060 0.076 0.080 Difference 0.076 0.043 0.062

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86 both soil depths. Yield of the tops was significantly greater for CSP'IAA than for CSP+IAA for the Athi soil. This shows that lAA depressed yield (Table 14). The tops weight for CSP-IAA was 23-4 g compared to 17' 7 g for CSP+IAA for the 15to 30-cra depth giving a yield difference of 5' 7 g; the values for the 0to 15-cm depth were 21*2 and 19 '8 g respectively, giving a yield difference of 1*4 g. The former (5*7 g) was significant (Table 15). Comparison of control and the other treatments for the soils shows that the tops weight for the former were significantly less than those for the other treatments only for Athi soil as shown in Table 16. The response of tops P was significantly greater for CSP than for lAA in all the soils as shown in Table 12, an effect which is further shown by both depths in Table 13. The plants on Athi and Mwea soils treated with CSP'IAA had significantly more tops P than the mean for the same soils treated with CSP+IAA, a reflection of some unfavorable, property of lAA in the latter treatment (Table 14). A similar observation is shown by both depths in Table 15, where tops P is more for the CSP'IAA treatment. The controls in all the soils had significantly less tops P than the other treatments, a reflection of the dominant effect of CSP over lAA (Table 16). Both CSP and CSP-IAA had linear effects on leaf P as shown in Table 17 which also shows that leaf P in the plants on the controls was significantly less than leaf P in the plants with the other treatments. This observation can be obtained when the

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87 mean for the controls are compared with that of the other treatments. One unexpected result of this study is that where CSP was applied tops %P was more than for leaf %P. This was unexpected because the tops consist of both leaf and wood, the latter of wliich should have less P content than the leaf. Tops P for the different CSP forms were higher than leaf P for the same corresponding CSP forms (that is CSP powder, CSP pellet, and CSP'IAA), as shown by Tables 10 and 17, considering the means of each form. However, it shouid be noted that the interaction of soil witli treatments might be a complicating factor for the tops P. There were no soil X treatment or depth x treatment interaction for leaf P. Athi and Kabete soils greatly responded to CSP and CSP*1AA treatments witli nil tlie CSIÂ’ rates as shown by the data for DA-IÂ’ in Table 1 when compared to those in Table 18. There really was a negligible response of Mwea soil to these treatments and rates since this soil was very high in DA-P orignially. It was difficult to determine the interaction of the soils on DA-P because of the enormous difference in DA-P between Mwea soil and the other soils. It is doubtful whether it would really be valid to use the data in Table 18 to calculate significant differences since Mwea soil has much higher DA-P than either Athi or Kabete soils. For the same reason, the interaction of soil depth with CSP source (Table 19) may or may not be significant though it is quite clear that there is no significant difference between the powder and the pellet forms in the 15to 30-cm depth. The data in Table 20

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88 Table 17. Means and significant responses for leaf P (in two soils) of Eucalyptus grandis and soil test P by DA and SB methods for three soils treated with lAA and CSP. Leaf DA SB Treatment comparisons Factor Rates P P P No. Type Leaf P DA P SB p kg/ha % ppm Sum of squares Treatments A* AA AA Control 0.094 182 5.6 lAA r2 0.107 179 6.3 1 1AA,L lAA r3 0.125 177 6.0 2 1AA,Q lAA r4 0.110 179 6.3 3 CSP form A A CSP powder r5 0.091 193 9.7 4 CSP,L AA AA AA CSP powder r6 0.112 205 11.7 5 CSP,Q CSP powder r7 0.135 235 24.5 6 Form X rate ,L CSP pellet r5 0.111 196 8.4 7 Form X rate ,Q CSP pellet r6 0.129 216 14.2 8 CSP-1AA,L AA AA AA CSP pellet r7 0.160 243 25.9 9 CSP-IAA, Q CSP-IAA r2+r5 0.115 187 9.3 10 lAA vs CSP AA AA CSP-IAA r3+r6 0.123 203 15.4 11 CSP-IAA vs CSP+IAA A AA CSP-IAA r4+r7 0.150 233 23.9 12 Control vs others A A AA A A Soils AA AA AA Athi 37.5 1 12.9 Mwea 0.113 554 Kabete 0.133 14.7 ' 17.0 Soils X treatments as above AA 1 2 3 4 5 b 7 8 9 10 11 12 ** A*

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89 Table 17-continued . Leaf DA SB Treatment comparisons P P P No. Type Leaf DA SB Factor Rates P p p kg/ha % ppm Sum of squares Depths as above ** ** Soils X treatments 1 2 3 ** 4 5 6 7 8 9 * * 10 11 12 and denote significance at the 0.05 and 0.01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).

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90 Table 18. Interaction of soils on mean DA-P values for linear responses to CSP treatments for eucalypt. CSP rates, kg/h a Soils 28 56 112 Means , ppm CSP only Athi 17.4 39.2 90.9 Mwea 556.0 576.0 593.0 Kabete 10.0 20.3 33.0 CSPÂ’IAA Athi 20.0 43.4 91.3 Mwea 530.0 552.0 583.0 Kabete 10.5 15.0 25.5 Table 19. Interaction of soil depth with soils for eucalypt for CSP form DA-P extracted from comparison. CSP source Soil depth, cm 0-15 15-30 Difference Means , ppm Powder 198 224 -26 Pellet 213 223 -10 Differences 15 1

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91 gives a picture similar to that in Tables 1 and 18 for DA-P. The content of DA-extractable P in Mwea soil makes it difficult to evaluate significant differences apart from the fact that this soil is much higher in DA-P than the other soils . Sodium bicarbonate (SB), as expected, extracts less P termed SB-P in most soils than did double acid and this was the case in the present study. However, SB extracted slightly more P from both CSPtreated and lAAtreated Kabete soil than did DA from the same soil with these treatments (Table 20). On the other hand, DA extracted much more P than SB did from Athi soil treated with CSP and lAA. This shows that the effectiveness of an extractant is partly Influenced by the soil used. It is therefore unwise to generalize on the suitability of the method used as this depends on the soils among other factors. There was no significant difference between mean leaf N for lAA and CSP treatments. Leaf N was 1*27% and 1*22% for these treatments respectively. For the soils, mean leaf N was 1-14% and 1*22% for Mwea and Kabete respectively. Thus, there was very little variation in leaf N between treatments (and also between the soils) . These results might have been expected because a lot of N fertilizers had been applied. Maize Experiment after Eucalypt Growth Factors At 2 weeks maize height did not show any interaction with soils and treatment and there was no interaction with depths and treatments, but there was a significant difference between the height for lAA

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92 Table 20. Interaction of soils on DA-P and SB-P for treatment comparison of CSP with lAA for soils used for eucalypt. Factor Athi Soils Mwea Kabete Mean value CSP 49.2 Mean , ppm DA-P 575.2 19.4 214.6 lAA 9.7 517.8 6.2 177.9 Difference 39.5 57.4 13.2 36.7 CSP 10.2 SB-P 21.3 10.8 lAA 3.1 9.3 CM • Difference 7.1 12.0 )

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93 alone (41*0 cm) and that for CSP alone (39-0 cm) as shown in Table 21. This is the opposite of what was found for eucalypt at 2 months. This comparison with eucalypt may be invalid due to the difference in aye of Llic two plants. it Is very .likely tliat, at 2 weeks, maize plants use very little P so that even if a large amount of this nutrient is present in soil, such young plants need or use little of it. This explanation may apply in a similar way to the significant difference between height of maize at 2 weeks for CSP'IAA treatment (38Â’ 1 cm) compared to CSP+IAA treatment (40*0) at that age. The maize on the Athi, Mwea, and Kabete soils had a mean height of 33*7, 35'2, and 48*1 respectively, (for treatments 5 through 10) at 2 weeks. The plants responded better to the Kabete soil. At 2 weeks, height for maize was 40.9 cm for 0to 15-cm depth and 37 '8 cm for 15to 30-cm depth but this difference was not significant. At 4 weeks since emergence, CSP rates caused significant linear effects on height (Table 21 and 22) and the mean height for Kabete soil was significantly higher than for tlie other soils for all the CSP rates. There were similar linear height responses to CSP-IAA rates for the soils (Table 21 and 23). Again, the mean height for Kabete soil was significantly greater than for the other soil for all the CSP'IAA rates. From these observations, it is quite clear that both CSP and CSPÂ’IAA had similar effects on maize height at 4 weeks. Furthermore, height had an interaction

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94 Table 21. Means and height of Zea mays responses to residual lAA and CSP applied to three soils. Height, weeks 2 4 6 Factor Rate Treatment comparisons No. Type Height, weeks 2 4 6 cm Sum of squares Treatments kg/ha ** AA Control 39.7 69.1 92.7 lAA r2 41.0 69.4 90.3 1 1AA,L lAA r3 41.3 68.8 90.6 2 1AA,Q lAA r4 41.0 69.2 91.3 3 CSP form CSP powder r5 39.1 72.7 100.1 4 CSP,L * AA CSP powder r6 39.7 75.2 104.2 5 CSP,Q CSP powder r7 39.1 74.5 104.5 6 Form X rate,L CSP pellet r5 39.2 72.6 100.3 7 Form X rate,Q CSP pellet r6 38.4 74.2 105.3 8 CSP-IAA, L ** AA CSP pellet r7 38.7 76.7 107.8 9 CSP-IAA, Q CSP-IAA r2+r5 36.7 71.0 100.6 10 lAA vs CSP alone * ** AA CSP-IAA r3+r6 39.5 74.9 103.7 11 CSP-IAA vs CSP+IAA A AA CSP'IAA r4+r7 38.1 76.7 108.9 12 Control vs others A* AA Soils (Treatments 5 to 10 only) AA AA AA Athi 33.7 68.4 100.3 Mwea 35.2 68.0 101.4 Kabete 48.1 86.6 109.4 Soils X treatments 1 as above AA AA 2 3 4 A 5 6 7 8 AA 9 10 AA AA 11 12 AA

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95 Table 21-continued. Height, weeks Treatment comparisons 2 4 6 Factor Rate No. Type Height , weeks 2 4 6 Sum of squares cm Depths A* *A *A Soil depths x treatments 1 * 2 3 4 5 6 7 8 ** 9 ** 10 A 11 A 12 * ** and denote significance at the 0.05 and 0.01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).

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96 Table 22. Interaction of soils with maize height at 4 weeks for comparison of linear response to CSP rates. Soils CSP 28 rates, kg/ha^ 56 112 Mean Athi 67.9 Means , cm 70.2 66 . 5 68.4 Mwea 67.7 67.1 68.7 68.0 Kabete 82.1 86.9 91.0 86.6 Significant difference between treatments (0.05 level) is 6.6 cm. Table 23. Interaction of soils with maize height at 4 weeks for comparison of linear response to CSP'IAA rates. Soils 28 CSP'IAA rates, 56 kg/ha 112 Mean Significant difference 0.05 level Means , cm cm 6 . 6 Athi 64.7 71.5 69.2 68.5 Mwea 67.2 68.8 67.1 67.7 Kabete 80.9 84.3 94.0 86.4 Mean 70.9 74.9 76.8 Table 24. Interaction of soils with maize height at 4 comparison of response to CSP and lAA alone, weeks for Soils Treatment means CSP lAA Difference Significant difference Athi Mwea Means , cm 68.4 65.1 3.3 68.0 68.6 0.3 86.6 73.7 12.9 0.05 level 4.2 Kabete

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97 with soil depth due to CSP'IAA (Table 21); the response was quadratic. The height was less where lAA alone was used in the Kabete soil than where CSP alone was used, but there was no difference between these treatments for each of the other soils. Each of the treatments CSP-IAA and CSP+IAA was 78*2 cm at 0to 15-cm depth and 69*5 cm at 15to 30-cm depth compared to values of 78*5 and 66*7 cm, respectively, for CSP+IAA; the significant difference for this comparison was 6*6. It is clear that growth was better in the 0to 15-cm depth. The mean height for the plants in the control was 69 •! compared to 73*0 cm for the other treatments and the mean height for Athi, Mwea, and Kabete, was 68‘4, 68' 0, and 86 "6 cm, respectively, considering treatments 5 through 10, in Table 21. The mean height for 0to 15-cm depth was 79 •! compared to 67*3 for the 15to 30-cm depth, an indication of better growth in the top soil. At 6 weeks after emergence, CSP pellet had a significant linear effect on height and CSP powder had no such effect. The mean height for the CSP powder corresponding to increasing rates were 100*1, 104*2, and 104.5 cm and those for CSP pellet were 100*3, 105*3, and 107*8. For a significant difference of 5*6, it is clear that there were no significant differences among the rates for CSP powder. These data are presented in Table 21 except for the above significant difference. The CSP* LAA also had a significant linear effect on height for which the means are 100*6, 103*7, and 108*7 (5*6 being the significant difference as

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98 above). There were significant interactions of all CSP-IAA rates with depths as shown in Table 25. In every case, there was greater height in the 0to 15-cm depth than in the lower depth. A comparison of CSP with lAA treatments alone shows that height was greater for CSP in all the soils (Table 26) . The height differences between these treatments were significant for two soils Athi and Kabete, being 16 ‘8 and 17 *6, respectively. The corresponding difference for Mwea soil was 6*3. Lack of significance for this soil is most likely due to a high level of P present. At 6 weeks since emergence, the mean height for CSP'IAA was significantly better than that for CSP+IAA, being 104*3 and 99*4 cm respectively (Table 21) . This difference is probably due to low values for lAA which depressed growth. Mean height for the control was 92*7 cm compared with 100*6 cm for the other treatment. The difference must be due to the positive effect of CSP on growth which also overcame the adverse effect of lAA alone. As for the previous weeks, there was better growth in height for the 0to 15-cm depth than in the lower depth (107*7 and 92*4 cm, respectively). As shown in Tables 27 and 28, there was an interaction of solJs with weight of maize tops due to CSP forms used. Tops weight for the pellet form was greater than that for CSP as powder in the case of Kabete soil but the corresponding differences for Athi and Mwea soils were not significant. Tops weight for Kabete soil was almost twice as large as for each of the other soils, comparing values corresponding to each of the CSP forms. There were

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99 Table 25. Interaction of soil depths on maize height at 6 weeks comparing linear response to CSP*1AA rates. CSP-IAA rates, kg/ha Significant Soil depth 28 56 112 difference cm Mean, cm 0.05 level 0-15 111.0 110.0 111.6 13.0 15-30 84.2 81.3 80.9 Difference 26.8 28.7 30.7 Table 26. Interaction of soils on maize height at 6 weeks comparing CSP with lAA treatments alone. Soils Treatments Significant CSP lAA Difference difference Athi Means, cm 0.05 level 13.0 100.3 83.5 16.8 Mwea Kabete 102.9 96.6 6.3 109.9 92.3 17.6 Kabete

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100 Table 27. Means and responses of tops weight and tops P of Zea mays and of soil test (DA) P to residual lAA and CSP treatments of three soils. Tops Tops DA Treatment comparisons weight P P No. Type Tops Tops DA Factor Rate weight P P kg/ha g % ppm Sum of squares Treatments ** * kk Control 9:1 0-095 158-5 lAA r2 10; 3 0-095 160-1 1 1AA,L lAA r3 9-8 0-095 162-0 2 1AA,Q lAA r4 10 '3 0-095 153-5 3 CSP form ** CSP powder r5 12-0 0-106 170-7 4 CSP,L ** ** kk CSP powder r6 14:4 0-120 183-1 5 CSP,Q CSP powder r7 16*5 0-143 204-9 6 Form X rate,L CSP pellet r5 13-3 0-109 174-1 7 Form X rate,Q CSP pellet r6 14-4 0-133 199-0 8 CSP-IAA, L ** * kk CSP pellet r7 18-4 0-153 213-6 9 CSP-IAA, Q CSP-IAA r2+r5 12-5 0-114 181-7 10 lAA vs CSP alone ** kit kk CSP-IAA r3+r6 14-5 0-129 199.-1 11 CSP-IAA vs CSP+IAA *>v k kk CSP-IAA r4+r7 17-5 0-161 212-2 12 Control vs others ** k kk Soils (Treatments 5 to 10 only) ** kk kk Athi 11-2 0-127 31-8 Mwea 11-9 0-169 528-1 Kabete 21-4 0-087 12-6 Soils X treatments ** kk kk ' 1 as above 2 3 ** 4 ** kk kk 5 6 7 k 8 Q kk y 10 ** kk kk 11 kk 12 ** k

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101 Table 27-continued. Factor Rate Tops Tops weight P DA P Treatment comparisons No. Type Tops Tops DA weiglit P P Depths 8 Soil depths x treatments % ppm as above 1 2 3 4 5 6 7 8 9 10 11 12 Sum of squares k * k kk and denote significance at the 0-05 and 0‘01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).

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102 Table 28. Interaction of of CSP forms. soils with maize tops weight for comparison CSP sources Significant Soils Powder Pellet Difference difference Means , g 0.05 level 0.96 Athi 11.1 11.3 0.2 Mwea 12.2 11.6 0.6 Kabete 21.8 23.3 1.5 Table 29. Interaction of soils with maize tops DA-P for comparison of linear effect weight, tops P, and of CSP rates. CSP rates, kg/ha Significant Soils 28 56 112 difference Means Tops weight i g 0.05 level 2.4 Athi 9.5 11.5 12.7 Mwea 12.0 11.1 12.7 Kabete 16.7 20.2 27.0 Tops P, % 0.014 Athi 0.100 0.122 0.160 Mwea 0.145 0.174 0.186 Kabete 0.078 0.086 0.099 DA-P , ppm 21.0 Athi 16.7 18.9 64.7 Mwea 498.0 542.0 544.0 Kabete 6.4 11.6 19.9

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103 significant linear effects of CSP rates on tops weight for Athi and Kabete soils, the latter being more significant (Table 29). Growth corresponding to each CSP rate was better in Kabete soil than in the other soils. The rates of CSP-IAA had linear interaction with tops weight in a way very similar to that of SCP rates (Table 30). As had been observed earlier in this discussion, growth was found to be better in all the soils treated with CSP than in those treated with lAA alone as the tops weight show in Table 31. Tops weight for CSPÂ’IAA was larger than that for CSP+IAA in Kabete soil but the reverse was true for Mwea soil. This suggests that growth depression by lAA alone (as far as tops weight for maize was concerned) was not as apparent in Mwea soil which was high in DA-P as it was in the other soils with low DA-P. Tops weight for CSP'IAA was not significantly different from that for CSP+IAA in Athi soil (Table 32) . It is shown in Table 33 that there was better growth for both control and the other treatments in Kabete soil than for these treatments in Athi and Mwea soils. Furthermore, it is shown that growth was less in the controls of Athi and Kabete soils than in the same soils with the other treatments. Although Mwea soil had a much higher DA-P, the mean tops weight for this soil was not different from that for Athi soil and was even lower than the mean tops weight for Kabete soil. The mean values for treatments 5 through 10 are shown in Table 27. There was better growth in the 0to 15-cm depth than in the lower depth. For these, the tops weight was 17*06 and 9-68 g respectively.

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104 The CSP rates had significant linear effects on tops P for the soils as shown in Tables 27 and 29. Although Table 29 shows that tops P for Kabete soil was less than for Athi and Mwea soils, caution should be exercised in their interpretation because of the differences in tops weight. Instead total uptake of P should be considered. The CSP-IAA rates had linear effect on tops P, similar to CSP rates (Table 30). As expected for all the soils, tops P was greater for CSP treatment than for lAA alone (Table 31) . There was a slight difference between tops P for CSP-IAA (0.135%) and that for CSP+IAA (0.117%) as shown in Table 27. Tops P for the controls for all the soils were significantly less than those for the other treatments. This was expected because the controls had no P treatment, an obvious requirement. Mean tops P for the control was 0.097% compared to 0.130% for the other treatments. Tops P for the soils as shown in Table 27 only give a partial picture because tops weight should be considered in interpreting them (tops weight were not the same between the soils). Tops P for the depths were 0.117% and 0.121% for 0to 15-cm and 15to 30-cm depths, respectively. It is shown in Table 27 that CSP rates had significant linear effects of DA-P for all the soils and the DA-P means for each rate and for each soil are shown in Table 29, which indicates significant differences among the rates for each of Athi and Mwea soil. Validity of the interpretation of the data for DA-P is complicated by the fact that Mwea soil had much higher P than the other soils. Because of this, the value to be used to determine

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105 Table 30. Interaction of soils on maize tops weight, tops P, and DA-P for linear response to CSP'IAA rates. CSP-IAA rates, kg/ha Soils 28 56 112 Significant difference Means 0.05 level Tops weight. g 2.4 Athi 8.8 12.5 12.0 Mwea 10.9 11.2 12.0 Kabete 17.9 20.0 28.5 Tops P, % 0.014 Athi 0.103 0.121 0.173 Mwea 0.157 0.176 1.201 Kabete 0.082 0.089 0.108 DA-P , ppm 21.0 Athi 13.6 20.4 59.4 Mwea 524.0 568.0 556.0 Kabete 7.5 8.9 21.4

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106 Table 31. Interaction of soils on maize tops weight, tops P, and DA-P for comparison of CSP and lAA alone. Soils Treatment comparison CSP lAA Difference Significant difference Mean 0.05 level 2.4 Tops weight , g Athi 11.2 6.5 5.7 Mwea 16.9 11.1 5.8 Kabete 17.8 11.4 6.4 Tops P, % Athi 0.127 0.073 0.054 Mwea 0.168 0.136 0.032 Kabete 0.088 0.074 0.014 DA-P , ppm Athi 31.7 4.9 26.8 Mwea 528.0 466.0 52.0 Kabete 12.6 4.3 8.3

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107 Table 32. Interaction of soils on maize tops weight, and DA-P for comparison of CSPÂ’IAA and CSP+IAA treatments. Soils Treatment comparison CSP-IAA CSP+IAA Difference Significant difference Athi 11.1 Means Tops weight, 8.9 g 2.2 0 . 05 level 2.4 Mwea 11.4 14.0 2.6 Kabete 22.1 14.6 7.5 Athi 31.1 DA-P , ppm 18.3 12.8 21 Mwea 549.0 497.0 52.0 Kabete 12.6 8.5 4.1 Table 33. Interaction of soils on maize top weight, tops P, and DA-P for comparison of control with the other treatments. Soils Treatment comparison Others Control Difference Significant difference Means Athi 10.0 Tops weight, g 6.3 3.7 2.4 Mwea 11.6 10.4 1.2 Kabete 19.5 12.4 7.1 Athi 0.117 Tops P, % 0.078 0.049 0.014 Mwea 0.163 0.136 0.027 Kabete 0.085 0.070 0.015 Athi 24.8 DA-P , ppm 6.7 18.1 21.0 Mwea 520.0 465.0 55.0 Kabete 10.5 4.4 6.1

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108 Table 34. Interaction of soil depths on DA-P extracted for comparison of CSP forms. Soil CSP forms Significant depth Powder Pellet Difference difference cm 0-15 15-30 Means 173 194 -21 200 197 3 0.04 level 17 Table 35. Interaction of soil depths on DA-P extracted for comparison of linear response to CSP forms. Soil P rate, kg/ha Significant depth 28 56 112 difference Means CSP powder , ppm 0-15 160 174 185 15-30 182 192 225 CSP pellet. ppm 0-15 161 204 217 15-30 187 193 210 0 . 05 level 21

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109 whether there are significant differences may be improperly too large for Athi and Kabete soils. The CSP-IAA rates had a linear effect on DA-P values which were very similar to those of CSP rates (compare data for DA-P in Tables 29 and 30). As expected, DA-P values from the soils treated with CSP were higher than those treated with lAA alone (Table 31) . Again, interpretation is complicated by the much larger DA-P in Mwea soils compared with the other soils. The inclusion of lAA alone in CSP+IAA treatment lowered DA-P in all the soils compared to CSP'IAA in the same soils (Table 32). Both these treatments indicated that Athi soil had much higher amounts of DA-P than Kabete soil with the same treatments. The DA-P in the controls was less than in the other treatments as the data in Table 33 shows. There is a close relationship between the DA-P data in Table 33 and those in Table 31 and 32 because of the similar treatments used. There was a slight interaction between depths and CSP forms on DA-P extracted (Table 34). Apparently, presence of CSP pellets contributed more to DA-extractable P in the 0to 15-cm depth than did the CSP powder. However, little or no significance can be attached to this observation because the means were based on soils vastly differing in DA-P, that is, Mwea on the one hand compared with Athi and Kabete on the other. The same reasoning should apply to the data in Table 35 which takes into account the rates and forms of CSP used. Apparently, there were linear responses of DA-P to CSP rates at both depths.

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110 Maize Experiment with Two Soils, Athi and Kabete , Treated with Fresh CSP and lAA Growth Factors At 2 weeks since emergence height response of maize to CSP alone was significantly better than for lAA, being 46 *0 and 40*4 cm respectively (Table 36). The opposite of this had been found for residual CSP and lAA for maize in the previous experiment after eucalpyt harvest. The probable explanation is that in the present study with the two soils, Athi and Kabete, the treatments were more recent so that CSP was more effective in promoting growth, while lAA depressed growth. The mean height for Kabete soil was greater than that for Athi soil (48 -2 and 43 ‘9 cm) respectively. There were no interactions with soils at 2 weeks. At 4 weeks since emergence, height responded linearly to CSP rates, being 92‘5, 92^^ and 98*8 cm, as shown in Table 36. Residual CSP had similar linear effects in the previous maize experiment. As before, height of the plants on Kabete soil were significantly greater than that of the Athi soil. Also as previously found in the other maize experiment and at 2 weeks in the present study, height response to CSP was significantly better than response to lAA, being 94*6 cm for the former compared to 75*6 cm for lAA. However, growth was significantly better in Kabete soil than in Athi soil for both CSP and lAA treatments (Table 37). The mean height corresponding to CSP'IAA was 94*4 cm, very similar to that for CSP alone, and the mean height for CSP+IAA was 88 '3 cm, higher than 75 ’6 for lAA alone. The difference in the value corresponding to CSP+IAA and lAA alone is undoubtedly due to the fact that CSP

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Ill Table 36. Means and significant responses for Zea mays height during 6 weeks grown on two soils treated with lAA and CSP, Factor Rate 2 weeks Height 4 6 weeks weeks Treatment comparison Comparison 246 No. Type weeks weeks weeks Mean , cm Sum of squares Treatment kg/ha * ** ** Control 38.7 75.6 100.0 lAA r2 39.9 76.6 101.6 1 1AA,L lAA r3 40.0 75.3 97.8 2 1AA,Q lAA r4 41.3 75.0 97.4 3 CSP form CSP powder r5 45.9 91.0 118.1 4 CSP,L ** * CSP powder r6 45.5 92.0 120.6 5 CSP,Q CSP powder r7 50.1 100.0 126.7 6 Form X rate ,L CSP pellet r5 45.9 93.9 121.6 7 Form X rate ,Q CSP pellet r6 40.0 92.9 119.6 8 CSP-IAA, L CSP pellet r7 49.0 97.6 124.1 9 CSP-1AA,Q CSP-IAA r2+r5 49.4 92.9 121.5 10 lAA vs CSP ** ** CSP-IAA r3+r6 46.1 95.1 122.6 11 CSP-IAA vs CSP+IAA ** ** CSP-IAA r4+r7 43.8 95.2 121.3 12 Control vs others ** ** Soils (Treatment 5 to 10 only) ** ** ** Athi 43.9 86.6 111.0 Kabete 48.2 102.6 132.6 Treatments x soils as above ** 1 2 3 4 5 6 7 8 9 10 ** ** 11 12 and denote significance at the 0*05 and 0-01 levels, respectively, and the letter L is for linear and Q for quadratic. Rates of lAA '(in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).

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112 in CSP+IAA treatment partially offset the unfavorable effect of lAA alone. The difference in mean height for CSP-IAA compared to CSP+IAA was significant. Difference in mean height for the control compared to the other treatments was significant (75*6 and 87 '5 cm respectively) . This simply means that CSP in the other treatments favored growth as expected. As for the previous weeks, there were significant height responses, at 6 weeks since emergence, to CSP rates. The means were 119*8, 120*1, and 125*A cm. Tlicre were Interactions of tlie soils on height for comparison of CSP and lAA treatments alone similar to those at 4 weeks as shown in Table 37. The effects of CSP'IAA and CSP+IAA were as significant at 6 weeks as they had been at 4 weeks, tlie only difference iiclng greater liclght at 6 weeks with 121*8 cm for CSP*1AA and 114*2 for CSP+IAA. The difference between these height means was significant . Furthermore, there was better growth in the other treatments compared to growth in the controls, 123*6 and 100*0 cm, respectively. The mean height for Athi (111*0 cm) was less than that for Kabete (132-6 cm) at 6 weeks, considering treatments 5 to 10 only (Table 36). There were significant linear effects of CSP rates to tops yield of maize on Kabete soil (Table 39) . The CSP powder gave a quadratic effect on tops yield and the pellet form did not. Tops yield for powder were 25*7, 27*6, and 32*4 g compared with 25-2, 30*7, and 33*1 g for the pellet form. There was less tops yield for lAA (14-2 g) than for CSP alone (29-1), quite a significant difference. Apparently, lAA had the same effect on yield as it had

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113 Table 37. Interaction of soils on maize height at 4 and 6 weeks for comparison of CSP to lAA treatments alone. Soils CSP Treatment lAA Difference Significant difference Mean, cm cm 0.05 level 4 w^eks 6.8 Athi 86.6 61.3 25.3 Kabete 102.6 90.2 12.4 6 weeks Athi 111.0 75.9 35.1 Kabete 132.6 122.3 10.3

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114 on height, while CSP had the opposite and favorable effects. The mean tops yield for CSP'IAA was 29 '9 g and that for CSP+IAA was 24 •! g, giving a picture very similar to that found between these sources for mean height. This difference was siginficant. Mean yield for the control was 12*2 g compared to 25*6 g for the other treatments. Thus, growth in the untreated soils was much less than for the other treatments. The CSP rates had significant linear effects on tops P (Tables 38 and 39) . Though Kabete soil had lower tops P than did Athi soil, the real situation in terms of total P uptake must be different because tops yield for Kabete soil > tops yield for Athi soil (Table 39). Similarly, CSP'IAA rates had significant linear effects on tops P for both soils as shown in Table 40. The P content of the tops showed a greater difference between tops P from CSP treatment than lAA treatment of Athi soils than that between the same treatments for Kabete soil. The differences were 0*097 and 0*031 %P, respectively (Table 41). This might simply reflect the fact that maize exhibited better P uptake on Kabete soil treated with lAA than in the other soils with the same treatment. This was also true for eucalypt. Tops P for CSP'IAA treatment was significantly greater than that for CSP+IAA (O' 146 and O'lll %P respectively) because of inclusion of lAA treatment alone in the latter. In both Athi and Kabete soils, there was significantly less tops P in the controls than in the other treatments.

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115 Table 38. Means and significant yield and tissue P responses for Zea mays grown on two soils treated with lAA and CSP. Tops Tops Leaf Treatment comparison Factor Rate yield P P No. Type Yield Tops Leaf P P g % % Sum of squares Treatment, kg/ha Control 12.2 0.086 0.072 kk lAA r2 14.8 0.081 0.061 1 1AA,L LAA r3 14.9 0.084 0.065 2 1AA,Q LAA r4 12.8 0.088 0.078 3 CSP form CSP powder r5 25.7 0.103 0.067 4 CSP,L ** 4fk kk CSP powder r6 27.6 0.134 0.096 5 CSP,Q CSP powder r7 32.4 0.197 0.144 6 Form X rate,L CSP pellet r5 25.2 0.111 0.082 7 Form X rate,Q k CSP pellet r6 30.7 0.141 0.111 8 CSP-IAA, L k* kk CSP pellet r7 33.1 0.200 0.129 9 CSP-IAA, Q CSP-IAA r2+r5 26.8 0.103 0.074 10 lAA vs CSP kk kk kk CSP-IAA r3+r6 30.9 0.135 0.103 11 CSP-IAA vs CSP+IAA**** CSP-IAA r4+r7 31.9 0.199 0.116 12 Control vs others * ** k Soils (Treatments 5 to 10 only) kk Athi 20.8 0.170 0.112 Kabete 37.5 0.126 0.098 Treatment x soils as above k 1 2 3 k 4 kk kk 5 6 7 kk 8 9 kk 10 kk 11 12 kk * ** and denote significance at the 0.05 and 0.01 level, respectively, and the letters L and Q stand for linear and quadratic, respectively. Rates of lAA (in text) are expressed progressively as r2, r3, and r4; those for CSP sources are expressed progressively as r5, r6, and r7 (in text).

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116 Table 39. Interaction of soils on maize tops yield and tops P for comparison of linear effect of CSP rates. Soils CSP 28 rate, kg/ha 56 112 Significant difference Mean 0.05 level Tops yield. g 4.5 Athi 18.9 21.4 21.9 Kabete 32.0 37.0 42.6 Tops P, % 0.018 Athi 0.112 0.152 0.245 . Kabete 0.103 0.125 0.153 Table 40. Interaction of soils on maize tops P for comparison of linear effect of CSP'IAA rates. Soils CSP-IAA rates, kg/ha 28 56 112 Significant difference % 0.05 level 0.018 Athi 0.104 0.155 0.234 Kabete 0.101 0.116 0.164 Table 41. Interaction of soils on maize tops P for comparison of CSP and lAA treatments. Treatments Soils CSP lAA Difference Significant difference % 0.05 level Athi 0.170 0.073 0.097 0.018 Kabete 0.127 0.096 0.031

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117 As Cor tops yield niid tops IÂ’ CSP rates had significant linear effects on leaf P (Table 38) . A comparison of CSP forms shows an interaction of soils on maize leaf P (Table 43) . There is no difference between sources but only between soils for CSP powder. Similar in effect to CSP, CSP'IAA rates had significant linear effects on leaf P, the values being 0*074, 0*103, and 0*116 %P, respectively. It is interesting to note that these values are lower than the corresponding values for tops P for the same treatment (Table 38), which were 0*103, 0*135, and 0*199 %P. This indicates that, for these soils, and the treatment used, the % P in tops > % P in leaves, which implies that the harder or woody material of the tops had a higher %P than did the leaves. Leaf P for lAA was 0*068% compared with 0*110% for CSP, a significant and expected difference. For the control, leaf P was 0*072 % compared with 0*093 % for the other treatment, also a significant difference (Table 38) . There is a close similarity between the effects of lAA and CSP on root weight and the effects they had on tops yield. This is wliat would be cxpcctoil CHpccln.lly because growLli of the roots directly affects growth of the tops. The parts which were immediately in direct and continued contact with the treatments were the roots. Thus, as was the case with the tops weight, growth was significantly better for CSP (6*39 g) than for lAA (3*37). As it was for tops weight, CSP rates had significant linear effect on root P. For soils effect, whereas Athi soil had higher tops P than Kabete soil for all CSP rates (Table 39), the reverse is true for root P as

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1J8 Table 42. Interaction of other treatment soils on maize tops P for with the control. comparison of Soils Others Treatments Control Difference Significant difference % 0.05 level Athi 0.180 0.068 0.112 0.018 Kabete 0.128 0.105 0.023 Table 43. Interaction of CSP forms. soils on maize leaf P for comparison of Soils Powder CSP form Pellet Difference Significant difference Athi Kabete 0.117 0.088 % — 0.107 0.107 0.010 -0.019 0.05 level 0.018

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119 shown in Table 45. This showed that % P in roots for Kabete soil > for Athi soil, comparing the means for each rate. In other words, root yield and root P content for Kabete > root yield and root P for Athi. The CSP'IAA rates had effects very similar to CSP rates for root P for both soils, except that, at the highest rate, 112 kg/ha, root % P for CSP*1AA > root % P for CSP (Table 46 data compared with those in Table 45). As expected, root P was significantly more for CSP treatment than for lAA as shown in Table 47 which also shows, as already pointed above, that root P for Kabete > root P for Athi for both CSP and lAA treatments. The forms of CSP in the soils significantly affected the amount of double acid-extractable P. For the powder form, the mean DA-P was 29-5 ppm compared with 41-3 ppm for the pellet form. The CSP rates (for both forms) had significant linear effects on DA-P which were 10 Â’8, 29*3, and 48*5 ppm for the powder compared with 11-0, 30' 2, and 83 '0 ppm for the pellet. The greater effect of the pellet form and rates on DA-P compared with the powder is probably a reflection of more difficulty in sampling a soil which has been treated with pelletized P fertilizer such as was used and indeed there was much more variability between replicates of the soil treated with CSP pellets. This variability is due to the fact that dissolution of the pellet and its distribution in the soil is much slower compared with that of the powder. Thus any soil samples taken from a soil which had been treated with pelletized superphosphate fertilizer are likely to have residual pellets. For this reason, there is likely to be a greater variation among the

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120 replicates with the highest rates of the fertilizer, as indicated by the values of 83*0 ppm of DA-P for the pellet compared with 48*5 ppm of DA-P for the powder form, corresponding to 112 kg P/ha rate as shown in Table 44. Such a sampling error is likely to be quite significant if sampling of soil is done within a few weeks or months following the fertilizer application and is likely to decrease after several years due to dissolution and distribution of the pellets. CSP rates had a significant quadratic effect on DA-P (Table 48). There was no significant difference between the soils with regard to the highest CSIÂ’ rate. Tlic diCfcrcncc between tlie two soils in the DA-P for the lower rates is probably partly due to errors due to sampling (that is, if some samples contain pellets). There were significant form x rate effects on DA-P as already referred to in the discussion about the linear effects of CSP rates, as stated above. It is clear that responses to both sources are linear with different slopes. The CSP*1AA rates had significant linear effects on DA-P for both soils (Table 46) .

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121 Table 44. Means and responses of root weight and root P of Zea mays and of double acid-extractable soil P for two soils receiving three rates of lAA and CSP sources. Root Root DA Comparisons Factor Rate weiglit P P No, Type Root Root DA weight P P g % ppm Sum of squares Treatment , kg /ha AA AA Control 2.75 0.041 6.8 lAA r2 3.29 0.040 6.3 1 1AA,L lAA r3 3.51 0.040 6.5 2 1AA,Q lAA r4 3.32 0.043 6.8 3 CSP form AA CSP powder r5 6.04 0.057 10.8 4 CSP,L A AA CSP powder r6 5.83 0.068 29.3 5 CSP,Q CSP powder r7 5.94 0.089 48.5 6 Form X rate :,L AA CSP pellet r5 5.25 0.057 11.0 7 Form X rate ,Q CSP pellet r6 6.10 0.071 30.2 8 CSP-IAA, L AA AA CSP pellet r7 5.87 01099 83.0 9 CSP-IAA, Q CSP-IAA r2+r5 5.78 0.057 17.2 10 lAA vs CSP A AA AA CSP-IAA r3+r6 6.27 0.069 26.5 11 CSP-IAA vs CSP+IAA CSP-IAA r4+r7 6.42 0.111 49.4 12 Control vs others Soils (Treatments 5 to 10 only) Athi 5.37 0.067 36.8 A Kabete 6.30 0.079 34.1 Soils X treatments as above 1 2 3 4 5 f) 7 8 9 10 11 12 :k :k:k and denote significance at the 0.05 and 0.01 probability level, respectively, and letter L is for linear and Q for quadratic effects. A* AA AA

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122 Table 45. Interaction of soils on maize root P for comparison of linear effect of CSP rates. CSP rates, kfi/ha Significant Soils 28 56 112 difference Means Root P . % Athi 0.046 0.062 0.095 Kabete 0.068 0.077 0.093 0.05 level 0.012 Table 46. Interaction of soils on maize root P and DA-P for comparison of linear effect of CSP'IAA rates. CSP-IAA rates, kg/ha Soils 28 56 112 Significant difference Means 0.05 level Root P, % 0.012 Athi 0.044 0.063 0.116 Kabet 0.070 0.075 0.106 DA-P , ppm 11.2 Athi 18.9 30.3 46.5 Kabete 15.5 22.8 52.2

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123 Table 47. Interaction of soils on maize root P for comparison of CSP with lAA treatments. Soils Treatments SiRnificant CSP lAA Difference difference Athi % P 0.05 level 0.068 0.026 0.042 0.012 Kabete 0.079 0.057 0.020 Table 48. Interaction of two soils on DA-P extracted in the maize experiment for comparison of quadratic effect of CSP rates. Soils CSP rates, ks/ha Significant 28 56 112 difference Athl Kabete 8.0 18.7 PPM 37.1 23.9 65.3 66.2 0.05 level 11.2

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REGRESSION RELATIONSHIPS Correlation between the various yields and corresponding plant and soil P values are presented in Table 49 where N is the sample size upon which the estimate r was based. The level of significance is indicated by P. Table 49. Correlation between yields and corresponding plant and soil P values. Variables N r P Wt, Eucalyptus P tops 234 0.286 <0.001 Wt, Eucalyptus DA-P 234 0.115 0.078 Wt, Eucalyptus SB-P 156 0.368 <0.001 Maize top Wt , (Residual P) Maize top P 234 -0.106 0.105 Maize top Wt, (Residual P) DA-P 234 -0.172 0.008 Maize Lop Wt, (l'Â’reHl) 1Â’) Maize top P 78 0.255 0.024 Maize top Wt, (I'resh P) Leaf P 78 0.247 0.030 Maize top Wt , (l''resh 1Â’) Root P 78 0.657 <0.001 Maize top Wt, (Fresh P) DA-P 78 0.441 <0.001 The highest correlation obtained was between maize top weight (from soils with fresh P) and root P (with p <0.001) in which r = 0Â’657. There was also a high correlation (r = 0'441) between maize top weight and DA-P. Weight yield of eucalyptus also had a high correlation with SB-P (r = 0Â’368) with p <0*001. The problem with the combined data presented in Table 49 is that there was a very large difference in P between Mwea soil on the one hand and Athi and Kabete soils on the other. Small variations in P from the means for Mwea soil, for example could 124

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125 have been very large compared to those in the other soils. This is considered one of the reasons for poor correlations among the variables except a few of them compared to those below for each soil . In view of this, it was thought appropriate to determine regression equations which could be used to predict such variables as tops P, leaf P, root P, and DA-P for each soil. The closer the r value is to ±1, the greater the correlation between the variables, and the better is the prediction for the dependent variable. In the following equations, tops P, leaf P, and root P are in %; DA=P and SB-P are in ppm. The symbols ** indicate significance at p = 0-01 and * indicates significance at p = 0*05, for 37 degrees of freedom (of the means of the variables considered). The equations have been partitioned under (i) Eucalypt Experiment, (ii) Maize Experiment with residual soil treatments, and (iii) Maize Experiment with new treatments. (i) Eucalyptus Experiment Athi Soil, 0to 15-cm depth Tops P = 0-082 + 0-00164 (DA-P) r = 0-843 t = 9-5** Tops P = 0-074 + 0-0060(SB-P) r = 0-794 t = 9-6** DA-P = 386 (SB-P) 6-30 r = 0-982 t =31-6**

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126 Athi soil, 15to 30-cm depth Tops P = 0*068 + 0*00134(DA-P) r = 0*915 t =13*8** Tops P = 0*061 + 0* 00135 (SB-P) r = 0*743 t = 6*75** DA-P = 8*11(SB-P) 16 r = 0*985 t =35*15** Mwea soil, 0to 15-cm depth Tops P = 0*0069 (DA-P) 0*243 r = 0*596 t = 4*52** Tops P = 0*090 + 1*40 (Leaf P) r = 0*838 t =72*8** Leaf P = 0*00033(DA-P) 0*068 r = 0*475 t = 3*28** Mwea soil, 15to 30-cm depth Tops P = 0*000868 (DA-P) 0*497 r = 0*74 t = 6*69** Kabete, 0to 15-cm depth Tops P = 0*114 + 0*00193 (DA-P) r = 0*593 t = 4-47** Tops P = 0*090 + 0*00278(SB-P) r = 0*782 t = 7*59** Tops P = 0*0168 + 0*970(Leaf P) r = 0*857 t =10*1** DA-P = 1*017(SB-P) 0*35 r = 0*926 t =14*9**

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127 Kabete soil, 15to 30-cm depth Tops P = 0-083 + 000408 (DA-P) r = 0-761 t = 6-08** Tops P = 0-071 + 0-0043(SB-P) r = 0-783 t = 7-68** DA-P = 1-02(SB-P) 2-43 r = 0-994 t =58-0** (ii) Maize, Residual Soil Treatments Athi soil, 0to 15-cm depth Tops P = 0-089 + 0-00104 (DA-P) r = 0-726 t = 6-44** Athi soil, 15to 30-cm depth Tops P = 0-084 + 0-00113(DA-P) r = 0-896 t =12-3** Mwea soil, 0to 15-cm depth Tops P = 0-076 + 0-00145 (DA-P) r = 0-371 t = 2-42* Mwea soil, 15to 30-cm depth Tops P = 0-00454(DA-P) 0-066 r = 0-564 t = 5-03** Kabete soil, 0to 15-cm depth Tops P = 0-080 + 0-000832 (DA-P) r = 0-645 t = 5-13** Kabete soil, 15to 30-cm depth Tops P = 0-0561 + 0-00335(DA-P) r = 0-319 t = 2-16*

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128 (iii) Maize, New Treatments Athi soil, 0to 15-cm depth Tops P = 0-092 + 000244 (DA-P) r = 0-95 t =18-5** Tops P = 0-005 + l-45(Leaf P) r = 0-820 t = 8-71** Tops P = l-645(Root P) 0-037 r = 0-812 t = 8-44** Root P = 0-023 + 0-00131 (DA-P) r = 0-945 t =17-7** Leaf P = 0-0534 + 0-772(Root P) r = 0-574 t = 4-26** Kabete soil, 0to 15-cm depth Tops P r t Tops P r t Leaf P r t Root P r t Leaf P r t 0-11 + 0-176 (DA-P) 0283 179 0-544 + 0-844(Root P) 0238 146 l-22(Root P) 0-001 0-80 8-14** 0-0117(DA-P) 0-179 0-765 7 21** 0-071 + 0-000675 (DA-P) 0-59 4-45** There are highly significant correlations between the variables, except a few. Since there are high correlations between DA-P and SB-P for the soils in which both methods of soil P determinations were used, it would be preferable to use the DA method because it is quicker and more convenient. The main disadvantage with the SB method is that the soil extracts are usually dark colored (due to

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129 organic matter extracted by the alkaline solution) so that they require organic matter removal with activated charcoal. This process is time-consuming. The above equations give a clear indication that it is inappropriate to determine correlations of the variables for all the soils especially if they have large differences between P. It is much better to determine correlation for individual soils and depths. For soils in which both DA and SB were used as extractants, it is found that values obtained by either soil test give similar slopes of the equations for prediction because DA-P and SB-P are highly correlated. In Kenya, the two methods which are most frequently used for soil P determination are DA and SB. 'J'hls research should show how to improve the interpretation of soil test results by using the regression relationships. These can be used as the starting point.

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CONCLUSIONS (1) Both Eucalyptus grand Is and Zea mays responded positively to rates of 28, 56, and 112 kg P/ha applied as CSP in either powder form or pellet form. Addition of lAA at preplant depressed grand is and stimulated mays growth. Since the reaction and persistence of lAA in these or other soils are unknown, the level of lAA employed may not have matched the need these species had for endogenous lAA. Presence of lAA in CSP did not affect plant responses above or below that for corresponding rates of CSP. (2) Phosphorus content of eucalypt and maize tops and leaves showed significant linear increases with respect to rates of applied CSP or CSP'IAA, showing that the fertilizer P was readily available to these species. The availability of P in the soil by DA-P or SB-P test was also highly correlated with the level of tops P so that soil test values appeared useful in predicting level of P in the plant. (3) Regression relationships between soil test P and tops P or leaf P appeared that data for each soil, rather than grouping those of several soils, should be used in obtaining correlations between soil test and tissue data. Knowing this, it should prove valuable in conserving the use of phosphate on soils either natively high in P or attaining sufficient P from past fertilization. For both eucalypt and maize, leaf P was lower than tops P so that choice of foliar tissue should be considered in obtaining correlation data. 130

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131 (4) From these studies, soils from eitlier depth responded to CSP rather similarly so that recommendations on land subject to shallow erosion could be expected to respond to P alike those of the same soil with negligible erosion. (5) Despite apparent P deficiency of plants grown on Athi and Kabete soils occurring shortly after emergence on control and lAA treatments, grandis seedlings grew to the same height as those with CSP on Kabete soil whereas they did not on Athi soil. This was also true for dry weight of tops on Athi soil compared to Kabete and Mwea soils. Under the flooding conditions, increased P availability of native P in Kabete soil may have promoted more growth than that in Athi soil or Mwea soil. Lack of linear or quadratic responses in dry weight of eucalypt seedlings to rates of the CSP forms suggested that 28 kg P/ha was sufficient compared to that supplied by the soils for lAA and control treatments. (6) Maize weight responses to residual P from the eucalypt experiment did show a linear response to rates of the CSP forms in Athi and Kabete soils, particularly for CSP-IAA. Increased weight of mnJzc tops nt 28 kg P/lm over that without CSP was greatest for Kabete soil, which also gave the highest maize dry matter at the 56 and 112 kg P/ha levels compared to corresponding treatments in Athi and Mwea soils . (7) Maize with preplant fertilization produced more dry weight on Kabete soil than Athi soil at each CSP rate of application. At 28 kg P/ha, dry matter was four times that without CSP in Athi soil and double that without CSP in Kabete soil.

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V -> >* _ T .'. -. '.7,'7 r S'.' V. APPENDIX >=3V " ..•'i

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Table 50. Mean height and stem thickness of eucalyptus grown on oto 15-cm depth of Athi soil treated with indole acetic acid (lAA) and three concentrated superphosphate (CSP) sources at three rates. Rate Height Months since emergence Stem thickness lAA P 2 3 4 cm mm Check 0 0 6.2 16.2 41.0 3.9 lAA 0.031 0 7.0 18.2 49.1 4.0 0.062 0 5.9 16.3 48.6 4.0 0.124 0 4.1 13.9 39.8 3.5 Powdered CSP 0 28 14.6 28.4 47.8 5.4 0 56 26.2 37.3 57.7 5.3 0 112 20.4 30.8 51.4 5.3 Pelletized CSP 0 28 22.7 35.0 62.9 6.1 0 56 19.5 30.4 60.7 5.3 0 112 24.1 34.8 55.1 5.9 Pelletized CSP with lAA 0.031 28 26.4 38.7 62.4 5.3 0.062 56 20.4 31.6 57.2 6.1 0.124 112 19.3 34.6 64.3 5.6 133

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134 Table 51. Mean height and stem thickness of eucalyptus grown on 15to 30-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate Height Months since emergence Stem thickness lAA P 2 3 4 kg/ ha cm mm Check 0 0 4.8 10.2 32.7 3.1 lAA 0.031 0 4.1 9.2 37.2 2.7 0.062 0 2.2 4.1 15.5 1.8 0.124 0 2.9 7.2 24.1 2.3 Powdered CSP 0 28 12.4 26.7 59.1 5.3 0 56 18.7 33.6 66.7 5.2 0 112 20.8 33.7 56.8 5.1 Pelletized CSP 0 28 21.4 32.7 58.2 6.0 0 56 19.5 34.1 63.4 4.8 0 112 22.1 34.8 64.1 6.1 Pelletized CSP with lAA 0.031 28 19.8 34.5 64.9 6.5 0.062 56 22.9 32.8 50.9 5.1 0.124 112 23.4 39.9 65.6 5.7

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135 Table 52. Mean height and stem thickness of eucalyptus grown on 0to 15-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Height Rate Months since emergence Stem thickness lAA P 2 3 4 kg/ ha cm mm Check 0 0 22.7 37.5 70.3 5.7 lAA 0.031 0 16.1 29.1 55.0 4.8 0.062 0 15.9 34.1 62.2 5.2 0.124 0 15.1 30.1 56.4 5.2 Powdered CSP 0 28 19.3 35.3 65.1 5.9 0 56 19.1 32.1 55.1 5.8 0 112 21.4 34.1 60.0 5.4 Pelletized CSP 0 28 18.2 31.1 58.4 5.8 0 56 20.5 35.5 67.6 5.7 0 112 17.1 31.8 58.1 5.4 Pelletized CSP with lAA 0.031 28 23.1 35.5 62.2 5.8 0.062 56 21.0 35.2 61.0 5.7 0.124 112 20.6 32.7 60.1 5.2

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136 Table 53. Mean height and stem thickness of eucalyptus grown on 15to 30-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate Height Months since emergence Stem thickness lAA P 2 3 4 kg/ha cm mm Check 0 0 15.2 26.7 49.0 5.3 lAA 0.031 0 8.0 18.3 51.9 4.1 0.062 0 11.2 23.8 50.9 5.3 0.124 0 10.5 25.0 55.3 4.9 Powdered CSP 0 28 21.6 35.7 56.8 5.5 0 56 22.3 40.1 71.6 5.8 0 112 18.9 31.2 57.6 5.7 Pelletized CSP 0 28 21.1 38.4 68.0 5.9 0 56 19.9 32.6 58.3 6.0 0 112 25.2 39.9 70.4 6.3 Pelletized CSP with lAA 0.031 28 19.2 36.6 68.9 5.8 0.062 56 22.8 36.1 64.4 5.8 0.124 112 21.3 33.7 54.8 5.6

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137 Table 54. Mean height and stem thickness of eucalyptus grown on 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates . Rate Heigh t Months since emergence Stem P 2 3 4 thickness kg /ha cm mm Check 0 0 14.3 31.9 61.6 5.9 lAA 0.031 0 10.6 26.9 56.0 5.4 0.062 0 6.0 23.4 51.4 4.8 0.124 0 7.1 27.4 66.7 5.3 Powdered CSP 0 28 16.7 38.9 67.8 6.8 0 56 17.6 33.5 60.9 6.2 0 112 21.6 39.4 71.9 6.1 Pelletized CSP 0 28 11.2 25.1 50.0 5.7 0 56 9.3 28.6 66.6 5.8 0 112 12.1 28.9 65.7 5.1 Pelletized CSP with lAA 0.031 28 6.4 22.9 58.1 5.1 0.062 56 7.6 24.7 59.2 5.5 0.124 112 9.4 25.8 56.1 5.8

PAGE 154

13R Table 55. Mean height and stem thickness of eucalyptus grown on 15to 30-cm depth of Kalicto soil treated with Indole acetic acid and tliree conceiiL ra I ml stipe r|)hospha I e sources at Lliree rates. Rate Height Months since emergence Stem thickness lAA P 2 3 4 kg/ha cm iniTi Check 0 0 10.9 30.3 55.8 5.9 lAA 0.031 0 4.1 22.3 69.9 4.8 0.062 0 5.2 24.6 69.4 4.9 0.124 0 5.9 23.7 60.9 5.0 Powdered CSP 0 28 12.4 27.7 52.3 5.4 0 56 16.4 33.4 61.8 5.7 0 112 15.8 31.6 62.0 5.1 Pelletized CSP 0 28 4.7 24.6 63.1 5.5 0 56 6.4 23.8 57.1 4.9 0 112 9.2 28.2 57.3 5.5 Pelletized CSP with lAA 0.031 28 11.4 30.0 62.7 5.7 0.062 56 7.8 26.2 50.9 5.4 0.124 112 8.6 30.8 65.0 5.6

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139 Table 56* Mean dry matter yield of eucalyptus tops from eucalyptus grown on three Kenya soils sampled at two depths and treated with indole acetic acid (lAA) and three concentrated superphosphate (CSP) sources at three rates. Dry matter yield of eucalyptus tops Rate Athi (cm) Mwea (cm) Kabete (cm) lAA P 0-15 15-30 0-15 15-30 0-15 15-30 uci Check 0 0 8.85 5.37 22.56 20.63 24.45 23.57 lAA 0.031 0 8.60 4.41 17.63 13.16 21.39 17.13 0.062 0 8.59 2.74 16.96 15.87 17.49 18. 76 0.124 0 6.15 3.00 19.56 18.32 19.93 18.57 Powdered CSP 0 28 22.81 18.96 22.48 21.85 33.77 23.00 0 56 22.81 22.37 22.18 25.42 25.64 25.58 0 112 22.73 20.31 24.71 22.82 31.10 19.90 Pelletized CSP 0 28 26.42 23.34 19.76 22.47 25.85 24.30 0 56 2188 16.26 23.47 25.12 22.16 23.71 0 112 28.55 26.34 20.95 25.92 22.23 26.30 Pelletized CSP with lAA 0.031 28 23.64 24.38 23.46 26.30 17.81 21.33 0.062 56 23.43 20.41 21.57 23.64 16.02 25.37 0.124 112 20.93 22.81 18.53 23.20 25.22 23.63

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140 Table 57. Mean analysis of eucalyptus tops sampled from 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated supcrphosplintc sources at three rates. Rate Eucalyptus top composition lAA P P Ca Mg K Cu Fe Mn Zn kg/ha % — Check 0 0 0.053 1.25 0.20 0.90 11 50 413 66 lAA 0.031 0 0.066 1.31 0.22 1.06 12 53 450 36 0.062 0 0.057 1.29 0.24 0.96 12 80 457 45 0.124 0 0.066 1.02 0.20 0.91 13 60 440 46 Powdered CSP 0 28 0.101 1.10 0.18 0.76 8 47 623 39 0 56 0.139 0.94 0.15 0.69 8 40 553 36 0 112 0.217 1.15 0.17 0.75 8 40 660 41 Pellet: Lzed CSP 0 28 0.116 1.05 0.16 0.68 7 53 553 34 0 56 0.181 1.06 0.15 0.79 8 50 607 34 0 112 0.218 1.07 0.16 0.66 9 53 793 43 Pelletized CSP with IM 0.031 28 0.123 1.13 0.16 0.73 9 50 740 38 0.062 56 0.155 1.04 0.16 0.73 8 53 520 32 0.124 112 0.221 1.03 0.15 0.75 9 57 537 39

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141 Table 58. Mean analysis of eucalyptus tops sampled from 15to 30-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Eucalyptus top composition P Ca Mg K Cu Fe Mn Zn — kg/ha — % Check 0 0 0.067 1.53 0.30 0.97 13 60 233 45 lAA 0.031 0 0.068 1.61 0.32 0.87 15 57 263 58 0.062 0 0.076 1.78 0.29 1.09 17 70 220 54 0.124 0 0.077 1.75 0.34 0.94 17 80 323 66 Powdered CSP 0 28 0.097 1 . 06 0.17 0.6 3 8 4 7 237 33 0 5 () 0 . 1 31) 1.04 0.16 0.64 8 40 300 3/ 0 112 0.205 1.04 0.15 0.59 8 40 307 49 Pel lei rlzed CSP 0 28 0.093 0.95 0.15 0.62 8 107 323 40 0 56 0.187 1.53 0.22 0.63 9 63 413 56 0 112 0.211 1.00 0.15 0.60 8 77 330 39 Pelletized CSP with lAA 0.031 28 0.095 0.92 0.14 0.54 7 37 300 36 0.062 56 0.152 1.12 0.17 0.53 7 43 300 46 0.124 112 0.198 1.12 0.17 0.58 9 43 370 50

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142 Table 59. Mean analysis of eucalyptus tops sampled from 0to 15-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P P Eucalyptus Ca Mg top composition K Cu Fe Mn Zn /o ppm Check 0 0 0.089 0.91 0.18 0.69 8 43 220 35 lAA 0.031 0 0.096 1.08 0.21 0.70 8 40 237 36 0.062 0 0.083 1.03 0.21 0.67 7 43 233 38 0.124 0 0.083 0.83 0.18 0.67 7 45 240 30 Powdered CSP 0 28 0.091 0.92 0.18 0.60 6 37 227 27 0 56 0.139 0.96 0.19 0.60 6 47 250 34 0 112 0.158 1.06 0.20 0.60 6 63 313 41 Pelletized CSP 0 28 0.109 1.00 0.18 0.66 6 37 250 30 0 56 0.154 0.94 0.19 0.71 6 47 260 36 0 112 0.181 0.88 0.18 0.60 6 40 210 31 Pelletized CSP with lAA 0.031 28 0.121 0.98 0.20 0.62 7 33 270 32 0.062 56 0.139 0.99 0.21 0.60 6 47 290 33 0.124 112 0.189 1.18 0.22 0.64 7 57 283 39

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143 Table 60. Mean analysis of eucalyptus tops sampled from 15to 30-cm depth of. Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P Eucalyptus top composition Ca Mg K Cu Fe Mn Zn kg/ha ppm Check 0 0 0.064 1.03 0.24 0.56 8 50 183 39 lAA 0.031 0 0.080 1.04 0.25 0.67 7 40 133 33 0.062 0 0.080 1.15 0.26 0.61 7 37 250 35 0.124 0 0.074 1.09 0.24 0.60 7 40 227 34 Powdered CSP 0 28 0.083 1.13 0.23 0.49 6 37 193 37 0 56 0.115 1.18 0.24 0.52 6 37 177 43 0 112 0.146 1.09 0.21 0.53 6 33 207 40 Pelletized CSP 0 28 0.096 1.07 0.23 0.46 6 53 190 41 0 56 0.119 1.17 0.23 0.48 6 40 193 35 0 112 0.160 1.10 0.22 0.51 6 80 253 32 Pelletized CSP with lAA 0.031 28 0.079 0.94 0.20 0.47 6 40 157 38 0.062 56 0.109 1.24 0.25 0.49 6 60 227 36 0.124 112 0.172 1.18 0.24 0.51 6 47 257 43

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1^4 Table 61. Mean analysis of eucalyptus tops sampled from 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superpliosphate sources at three rates. Rate lAA P P Eucalyptus top composition Ca Mg K Cu Fe Mn Zn /o ppm Check 0 0 0.109 0.95 0.17 0.69 9 40 133 32 lAA 0.031 0 0.142 1.03 0.19 0.82 12 47 137 42 0.062 0 0.168 1.07 0.20 0.96 11 53 193 38 0.124 0 0.132 1.10 0.19 0.90 10 37 113 34 Powdered CSP 0 28 0.098 0.92 0.18 0.68 8 40 117 26 0 56 0.147 0.91 0.17 0.77 7 40 90 31 0 112 0.181 1.07 0.18 0.84 8 37 150 34 Pelletized CSP 0 28 0.147 0.96 0.17 0.81 8 53 117 33 0 56 0.171 0.95 0.17 0.88 8 40 93 34 0 112 0.187 0.82 0.14 0.81 8 73 90 30 Pelletized CSP with lAA 0.031 28 0.155 0.94 0.17 0.92 10 47 130 30 0.062 56 0.160 0.84 0.15 0.85 8 40 103 26 0.124 112 0.192 1.08 0.19 0.94 9 43 127 33

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145 Table 62. Mean analysis of eucalyptus tops sampled from 15to 30-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. R^te Eucalyptus top composition lAA P P Ca Mg K Cu Fe Mn Zn kg/ha % Check 0 0 0.051 1.11 0.18 0.77 7 40 230 38 lAA 0.031 0 0.076 1.20 0.19 0.84 9 40 213 43 0.062 0 0.057 1.29 0.22 0.99 10 43 250 48 0.124 0 0.057 1.21 0.22 0.96 11 40 243 41 Powdered CSP 0 28 0.117 1.18 0.19 0.69 8 47 237 42 0 56 0.141 1.09 0.17 0.67 9 43 217 40 0 112 0.212 1.33 0.18 0.79 8 37 210 38 Pelletized CSP 0 28 0.122 1.32 0.22 0.90 9 47 237 48 0 56 0.145 1.11 0.18 0.76 7 37 210 37 0 112 0.180 1.19 0.20 0.80 7 43 213 35 Pelletized CSP with lAA 0.031 28 0.101 1.10 0.16 0.73 6 43 180 33 0.062 56 0.143 1.12 0.17 0.73 7 37 267 41 0.124 112 0.169 1.10 0.18 0.73 7 43 177 32

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146 Table 63. Mean analysis of eucalyptus leaves sampled from eucalyptus trees grown on the 0to 15-cm depth of Mwea soil treated with indole acetic acid and three concentrated superphosphate sources at three r.ates. Rate lAA Eucalyptus leaf composition Ca Mg K Cu Fe Mn Zn kg/ha ppm Check 0 0 0.095 1.10 0.35 0.73 8 43 363 42 lAA 0.031 0 0.100 1.20 0.34 0.67 8 40 357 42 0.062 0 0.097 1.19 0.38 0.74 8 40 380 51 0.124 0 0.087 0.87 0.30 0.72 7 33 327 33 Powdered CSP 0 28 0.085 1.00 0.32 0.54 6 37 320 33 0 56 0.109 1.01 0.33 0.61 6 40 343 41 0 112 0.118 1.15 0.31 0.56 6 50 420 47 Pelletized CSP 0 28 0.110 1.12 0.34 0.65 6 37 370 35 0 56 0.110 1.04 0.31 0.69 7 40 360 42 0 112 0.137 1.21 0.36 0.72 7 60 390 37 Pellet 3 zed CSP with lAA 0.031 28 0.101 0.97 0.32 0.64 6 37 383 37 0.062 56 0.112 0.98 0.32 0.62 6 33 413 35 0.124 112 0.148 1.21 0.37 0.66 7 40 447 44

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Table 64. 14 7 Mean analysis of eucalyptus leaves sampled from eucalyptus trees grown on the 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates . Rate lAA P P Eucalyptus Ca Mg leaf composition K Cu Fe Mn Zn kp/ha °/ /o ppm Check 0 0 0.094 0.79 0.26 0.74 9 37 153 36 lAA 0.031 0 0.114 Q.89 0.29 0.83 10 35 187 45 0.062 0 0.152 0.96 0.31 1.00 11 60 277 45 0.124 0 0.137 1.10 0.37 1.04 10 47 173 39 Powdered CSP 0 28 0.098 0.84 0.31 0.71 9 35 150 28 0 56 0.116 0.77 0.28 0.83 8 40 130 38 0 112 0.154 1.04 0.34 0.97 8 33 240 38 Pelletized CSP 0 28 0.113 0.77 0.25 0.83 7 37 143 31 0 56 0.148 0.92 0.30 0.97 9 43 144 38 0 112 0.182 0.92 0.30 1.10 8 33 150 39 Pelletized CSP with lAA 0.031 28 0.129 0.84 0.32 0.97 9 40 167 35 0.062 56 0.134 0.87 0.33 0.97 9 40 173 33 0.124 112 0.152 1.09 0.34 1.03 9 60 187 36

PAGE 164

148 Table 65. Mean analysis of 0to 15-cm depth of Athi soil sampled after eucalyptus growth treated with indole acetic acid (lAA) and three concentrated superphosphate (CSP) sources at three rates. Rate lAA P P extracted Extractable cations by DA method DA SB Ca Mg K Cu Zn — kg/lia PPi'i -z • ppm Check 0 0 7.7 3.3 0.46 0.055 0.028 1.4 9.1 lAA 0.031 0 5.6 3.4 0.47 0.057 0.028 1.2 8.4 0.062 0 7.4 3.2 0.48 0.056 0.029 1.4 9.1 0.124 0 7.8 3.5 0.4 7 0.055 0.029 .1 . 0 6.0 Powdered CSP 0 28 16.0 6.7 0.46 0.055 0.021 1.6 9.0 0 56 19.0 7.0 0.47 0.059 0.022 1.6 7.8 0 112 70.5 21.3 0.47 0.055 0.022 1.7 10.0 Pelletized CSP 0 28 9.5 4.4 0.46 0.057 0.023 1.2 7.9 0 56 27.2 8.4 0.48 0.056 0.023 1.1 6.7 0 112 85.7 22.9 0.49 0.059 0.021 1.1 6.0 Pelletized CSP with lAA 0.031 28 14.9 5.3 0.47 0.059 0.022 1.7 10.3 0.062 56 45.0 12.7 0.47 0.055 0.023 1.0 5.7 0.124 112 77.5 22.3 0.49 0.058 0.024 1.0 6.8

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1^9 Table66. Mean analysis of 15to 30-cm depth of Athi soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. P extracted Extractable cations by DA method lAA P DA SB Ca Mg K Cu Zn Check to — ppm 0 0 10.9 2.7 0.53 0.054 0.019 0.8 3.9 lAA 0.031 0 16.3 3.1 0.54 0.058 0.019 0.8 4.8 0.062 0 8.8 3.1 0.55 0.061 0.020 0.8 5.4 0.124 0 12.2 2.5 0.55 0.059 0.019 0.9 3.9 Powdered CSP 0 28 23.6 3.7 0.53 0.055 0.016 1.1 6.4 0 56 52.5 6.8 0.53 0.055 0.013 1.2 4.8 0 112 96.2 15.2 0.55 0.056 0.013 1.4 5.9 Pelletized CSP 0 28 20.2 3.7 0.54 0.055 0.015 1.0 5.4 0 56 58.0 6 . 6 0.54 0.056 0.015 1.0 5.7 0 112 11.5 15.9 0.55 0.058 0.014 1.2 5.7 Pelletized CSP with lAA 0.031 28 25.2 3.8 0.56 0.056 0.015 1.0 5.7 0.062 56 41.7 7.2 0.53 0.055 0.015 1.2 5.4 0.124 112 105.0 16.0 0.57 0.059 0.015 0.9 6.3

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150 Table 67... Mean analysis of 0to 15-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P P extracted Extractable cations by DA method DA Ca Mg K Cu Zn Ira /ha ppm /o ppm Check 0 0 512 0.72 0.121 0.013 1.0 6.9 lAA 0.031 0 500 0.69 0.122 0.015 1.0 6.1 0.062 0 493 0.68 0.118 0.017 0.9 6.3 0.124 0 497 0.69 0.122 0.013 0.9 6.1 Powdered CSP 0 28 513 0.70 0.120 0.014 0.9 5.5 0 56 528 0.70 0.123 0.014 1.0 6.6 0 112 567 0.68 0.120 0.013 0.9 6.3 Pelletized CSP 0 28 548 0.71 0.125 0.015 0.9 6.7 0 56 1 572 0.73 0.129 0.012 1.1 7.5 0 112 595 0.72 0.126 0.014 0.8 4.6 Pelletized CSP with lAA 0.031 28 498 0.69 0.122 0.014 1.1 7.6 0.062 56 543 0.70 0.125 0.014 0.8 4.4 0.124 112 560 0.69 0.119 0.014 0.8 3.5

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15 1 Table 68. Mean analysis of 15to 30-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. P extracted Extractable cations by DA method lAA P DA Ca Mg K Cu Zn kg/ha ppm % ppm Check 0 0 550 0.75 0.143 0.007 0.8 7.3 lAA 0.031 0 537 0.76 0.144 0.009 0.8 5.7 0.062 0 538 0.73 0.136 0.009 1.0 9.1 0.124 0 542 0.74 0.140 0.007 0.8 7.3 Powdered CSP 0 28 583 0.74 0.141 0.008 1.0 10.2 0 56 600 0.74 0.136 0.006 0.7 6.2 0 112 617 0.73 0.136 0.008 0.9 10.3 Pelletized CSP 0 28 582 0.76 0.139 0.009 0.8 8.6 0 56 603 0.73 0.136 0.007 0.8 7.8 0 112 593 0.73 0.133 0.006 0.7 4.0 Pelletized CSP with lAA 0.031 28 562 0.73 0.141 0.008 0.7 5.4 0.062 56 560 0.73 0.139 0.007 0.7 4.8 0.124 112 607 0.73 0.141 0.007 0.8 5.3

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152 Table 69. Mean analysis of 0to 15-cm depth of Kabete soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P P extracted Extractable cations by DA method DA SB Ca Mg K Cu Zn ppm /o ppm Check 0 0 8.2 13.0 0.55 0.065 0.055 0.7 64 lAA 0.031 0 11.0 15.1 0.59 0.067 0.068 0.7 64 0.062 0 9.5 14.2 0.55 0.061 0.072 0.8 54 0.124 0 11.0 15.5 0.60 0.072 0.067 0.7 59 Powdered CSP 0 28 15.6 19.8 0.59 0.064 0.055 0.7 53 0 56 19.3 22.6 0.56 0.065 0.060 0.7 59 0 112 35.7 35.1 0.56 0.062 0.056 0.8 58 Pelletized CSP 0 28 15.4 18.9 0.56 0.065 0.062 0.7 55 0 56 24.5 29.3 0.60 0.070 0.063 0.8 77 0 112 40.8 34.8 0.60 0.068 0.061 0.7 62 Pelletized CSP with lAA 0.031 28 15.2 19.1 0.59 0.06 7 0.066 0.7 55 0.062 56 22.1 31.1 0.56 0.070 0.070 0.7 56 0.124 112 32.0 35.1 0.56 0.067 0.061 0.6 57

PAGE 169

153 Table 70. Mean analysis of 15to 30-cm depth of Kabete soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P P extracted Extractable cations by DA method DA SB Ca Mg K Cu Zn /o ppm Check 0 0 1.6 3.3 0.39 0.046 0.051 0.8 37 lAA 0.031 0 1.8 3.6 0.37 0.043 0.048 0.7 34 0.062 0 2.0 3.6 0.38 0.044 0.052 0.8 32 0.124 0 2.0 3.5 0.39 0.043 0.050 0.7 29 Powdered CSP 0 28 5.3 8.6 0.37 0.043 0.045 0.7 32 0 56 8.0 10.7 0.37 0.042 0.045 0.7 34 0 112 26.3 26.3 0.38 0.043 0.043 0.6 35 Pelletized CSP 0 28 3.7 6.5 0.38 0.042 0.046 0.6 32 0 56 9.4 12.3 0.37 0.042 0.045 0.8 33 0 112 28.9 30.2 0.39 0.044 0.046 0.7 40 Pelletized CSP with lAA 0.031 28 5.9 8.9 0.39 0.045 0.048 0.7 32 0.062 56 7.9 10.4 0.38 0.041 0.044 0.7 34 0.124 112 18.9 22.3 0.38 0.043 0.048 0.7 32

PAGE 170

154 Table 7,''., Mean analysis of 0to 15-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P Extractable cations by N NH4CI method Ca Mg K Na kg/ha X Check 0 0 0.78 0.15 0.020 0.012 lAA 0.031 0 0.79 0.16 0.021 0.010 0.062 0 0.87 0.17 0.023 0.010 0.124 0 0.94 0.17 0.020 0.011 Powdered CSP 0 28 0.91 0.16 0.020 0.011 0 56 0.89 0.16 0.020 0.010 0 112 0.95 0.18 0.019 0.010 Pelletized CSP 0 28 0.95 0.18 0.021 0.010 0 56 0.96 0.18 0.018 0.010 0 112 0.95 0.17 0.019 0.010 Pelletized CSP with lAA 0.031 28 0.90 0.16 0.020 0.010 0.062 56 0.95 0.17 0.020 0.011 0.124 112 0.94 0.16 0.020 0.010

PAGE 171

155 Table 72. Mean analysis of 15to 30-cm depth of Mwea soil sampled after eucalyptus growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P Extractable ! cations by N NH 4 CI method Ca Mg K Na kg/h «V a /o Check 0 0 0.95 0.19 0.012 .006 lAA 0.031 0 0.97 0.19 0.015 .006 0.062 0 0.95 0.20 0.015 .005 0.124 0 0.97 0.20 0.012 .006 Powdered CSP 0 28 0.92 0.19 0.012 .005 0 56 0.97 0.19 0.011 .005 0 112 0.99 0.19 0.014 .007 Pelletized CSP 0 28 0.96 0.20 0.013 .005 0 56 0.97 0.20 0.012 .005 0 112 0.97 0.21 0.011 .006 Pelletized CSP with lAA 0.031 28 0.94 0.20 0.012 .006 0.062 56 0.99 0.20 0.012 .005 0.124 112 0.94 0.20 0.012 .005

PAGE 172

156 Table 73. Mean height of maize grown on 0to 15-cm depth of undisturbed Athi soil with treatments previously used for eucalyptus. Height Rate Weeks since emergence lAA P 2 4 6 Check cm 0 0 37.7 59.3 79.0 IM 0.031 0 45.5 73.9 88.5 0.062 0 36.8 65.3 89.0 0.124 0 42.0 67.0 86.9 Powdered CSP 0 28 31.0 70.8 100.8 0 56 42.0 77.9 108.5 0 112 36.1 71.9 104.1 Pelletized CSP 0 28 34.5 69.7 102.5 0 56 37.8 72.1 106.5 0 112 33.3 72.6 109.8 Pelletized CSP with lAA 0.031 28 33.9 70.6 104.7 0.062 56 33.0 71.9 105.3 0.124 112 30.9 68.7 103.6

PAGE 173

157 Mean height of maize grown on 15to 30-cm depth of undisturbed Athi soil with treatments previously used for eucalyptus. Height Weeks since emergence 2 4 6 kg/h Check cm 0 0 35.2 63.3 84.6 lAA 0,031 0 40.4 61.1 78.2 0.062 0 43.9 64.1 81.8 0.124 0 35.2 59.2 76.6 Powdered CSP 0 28 32.9 64.9 90,6 0 56 31 .2 63.9 95.5 0 112 28.2 58.7 93.0 Pelletized CSP 0 28 33.8 66.1 92.7 0 56 30.5 67.0 100.1 0 112 33.4 65.0 99.1 Pelletized CSP with lAA 0.031 28 29.4 59.0 85.8 0.062 56 36.2 71.0 96.8 0.124 112 31.6 69.8 104.0 Rate lAA P

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158 Table 75 .. Mean height of maize grown on 0to 15-cm depth undisturbed Mwea soil with treatments previously for eucalyptus. of used Height Rate Weeks since emergence lAA P 2 4 6 ts,^/ ll< cm Check 0 0 39.2 74.4 108.0 lAA 0.031 0 34.1 68.3 98.3 0.062 0 40.4 70.9 99.9 0.124 0 40.7 74.9 102.7 Powdered CSP 0 28 43.0 73.8 107.0 0 56 36.3 70.0 104.6 0 112 37.6 69.4 102.0 Pelletized CSP 0 28 41.3 71.4 102.3 0 56 31.3 69.2 107.5 0 112 37.6 71.8 105.1 Pelletized CSP with lAA 0.031 28 33.8 71.2 104.2 0.062 56 32.6 67.9 108.9 0.124 112 32.8 69.3 104.9

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159 Table 76. Mean height of maize grown on 15to 30-cm depth of undisturbed Mwea soil with treatments previously used for eucalyptus. Height Rate lAA P Weeks 2 since ( 4 emergence 6 11. cm Check 0 0 32.2 62.4 89.7 lAA 0.031 0 36.0 66 . 0 92.9 0.062 0 34.9 65.2 90.8 0.124 0 36.8 66.1 94.8 Powdered CSP 0 28 32.1 66.1 98.7 0 56 33.4 64.0 97.4 0 112 33.5 66.7 99.8 Pelletized CSP 0 28 33.0 61.1 92.0 0 56 33.0 65.1 99.4 0 112 30.1 66.9 101.5 PclJetlzcd CSIÂ’ with lAA 0.031 28 30.7 63.1 95.8 0.062 56 36.5 69.7 95.8 0.124 112 27.1 64.8 101.2

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160 Table 77. Mean height of maize grown on 0to 15-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus. Height R^te Weeks since emergence lAA P 2 4 6 kg /ha cm Check 0 0 47.2 88.1 116.4 lAA 0.031 0 45.1 83.1 111.5 0.062 0 48.4 86.6 112.2 0.124 0 47.2 85.7 114.2 Powdered CSP 0 28 49.0 91.1 119.2 0 56 50.0 99.2 124.3 0 112 51.3 100.9 125.9 Pelletized CSP 0 28 48.4 94.9 120.3 0 56 49.7 95.7 .1 ] 9 . 8 0 ] 12 50 . 4 1 01.7 125.4 Pelletized CSP with lAA 0.031 28 48.7 92.9 124.2 0.062 56 50.9 90.0 115.3 0.124 112 55.2 101.8 126.4

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161 Table 78Mean height of maize grown on 15to 30-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus. Height Rate Weeks since emergence lAA P 2 4 6 cm Check 0 0 47.0 67.1 78.4 lAA 0.031 0 45.1 64.2 72.7 0.062 0 43.5 60.6 70.1 0.124 0 CM 62.5 72.8 Powdered CSP 0 28 46.5 69.6 84.7 0 56 45.3 76.7 94.6 0 112 47.9 79.6 102.7 Pelletized CSP 0 28 43.9 72.6 91.9 0 56 47.8 75.8 98.4 0 112 47.4 82.1 106.0 Pelletized CSP with lAA 0.031 28 43.9 68.9 89.0 0.062 56 47.7 78.7 100.0 0.124 112 50.8 86.1 113.3

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162 Table 79. Mean dry matter yield of maize tops grown on Kenya soils undisturbed after treatments previously used for eucalyptus. Rate Dry matter yield of maize tops Athi (cm) Mwea (cm) Kabete (cm) lAA P 0-15 15-30 0-15 15-30 0-15 15-30 K-g/ iia g Check 0 0 6.59 6.07 12.31 8.53 19.74 5.13 lAA 0.031 0 8.29 5.19 11.66 9.63 22.14 5.10 0.062 0 6.84 6.47 12.92 9.40 18.69 4.51 0.124 0 7.30 4.95 12.41 10.65 21.84 4.71 Powdered CSP 0 28 9.09 8.83 15.54 9.39 22.20 7.16 0 56 13.92 9.26 13.72 9.73 28.93 10.77 0 112 15.47 9.97 14.14 11.01 32.48 15.98 Pelletized CSP 0 28 11.64 8.21 13.25 9.55 27.98 9.22 0 56 13.60 9.08 11.58 9.42 29.55 13.41 0 112 12.52 12.66 14.34 11.35 40.10 19.57 Pelletized CSP with lAA 0.031 28 9.85 7.67 12.87 9.00 27.19 8.69 0.062 56 12.60 12.37 13.50 8.75 26.69 13.34 0.124 112 12.36 11.72 13.63 10.38 36.04 20.87

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163 Table O CO Mean analysis of maize tops undisturbed Athi soil with eucalyptus . sampled from 0to 15 treatments previously -cm depth used for of Rate P Maize top composition Fe Mn Zn lAA p Ca Mg K Cu ^ . H Of ;id /o ppm Check 0 0 0.076 0.43 0.18 3.80 7 73 61 30 lAA 0.031 0 0.068 0.45 0.20 3.67 6 53 56 27 0.062 0 0.079 0.39 0.19 4.33 6 45 58 29 0.124 0 0.072 0.42 0.19 4.33 7 87 58 31 Powdered CSP 0 28 0.101 0.37 0.16 4.03 7 65 61 29 0 56 0.113 0.41 0.16 2.73 5 53 59 26 0 112 0.138 0.49 0.16 2.43 6 40 64 20 Pelletized CSP 0 28 0.098 0.56 0.14 3.10 6 53 52 21 0 56 0.117 0.54 0.16 2.80 6 57 57 19 0 112 0.165 0.56 0.15 2.70 6 50 59 20 Pelletized i CSP with lAA 0.031 28 0.102 0.55 0 . 1 5 4 . 1 0 7 70 52 24 0.062 56 0.131 0.55 0. 16 3.40 6 73 58 23 0.124 112 0.170 0.51 0.14 3.53 6 60 56 21

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164 Table 81. Mean analysis of maize tops sampled from 15~ to 30— cm depth of undisturbed Athi soil with treatments previously used for eucalyptus . Rate lAA P Maize top composition Ca Mg K Cu Fe Mn Zn Check 0 0 0.081 0.56 0.22 3.10 7 63 28 36 lAA 0.031 0 0.077 0.49 0.26 2.53 8 50 35 46 0.062 0 0.076 0.57 0.27 2.09 8 97 36 46 0.124 0 0.079 0.61 0.24 2.57 8 80 33 41 Powdered CSP 0 28 0.099 0.51 0.24 1.55 8 53 38 34 0 56 0.128 0.49 0.26 0.62 7 70 38 29 0 112 0.158 0.56 0.24 0.91 6 47 40 28 Pelletized CSP 0 28 0.101 0.51 0.24 1.47 1 53 37 33 0 56 0.126 0.53 0.19 1.32 6 73 33 26 0 112 0.177 0.49 0.24 0.69 4 45 44 25 Pelletized CSP with lAA 0.031 28 0.104 0.47 0.23 1.44 7 67 38 33 0.062 56 0.111 0.45 0.22 0.75 6 73 38 25 0.124 112 0.177 0.48 0.18 0.85 5 47 34 23

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163 Table 82. Mean analysis of maize tops sampled from 0to 15-cm depth of undisturbed Mwea soil with treatments previously used for eucalyptus . Rate P Maize top composition Fc Mil Zn lAA P Ca Mg K Cu aj kg /ha /o Check 0 0 0.129 0.48 0.34 1.40 6 60 46 29 lAA 0.031 0 0.128 0.41 0.34 1.41 7 113 46 28 0.062 0 0.128 0.41 0.32 0.47 6 90 46 26 0.124 0 0.136 0.47 0.35 1.39 6 45 49 27 Powdered CSP 0 28 0.132 0.40 0 . 30 1.22 6 60 49 21 0 56 0.155 0.56 0.31 1.23 6 53 44 25 0 112 0.177 0.77 0.32 1.16 5 43 54 23 Pelletized CSP 0 28 0.138 0.75 0.32 1.30 5 80 43 23 0 56 0.176 0.60 0.36 1.31 7 53 47 34 0 112 0.167 0.66 0.28 0.86 4 80 42 20 Pelletized CSP with lAA 0.031 28 0.139 0.68 0.31 1.23 6 60 46 22 0.062 56 0.151 0.57 0.31 1.26 5 63 49 24 0.124 112 0.181 0.44 0.28 1.20 5 67 49 22

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166 Table 8.3,. Mean analysis of maize tops sampled from 15to 30-cm depth of undisturbed Mwea soil with treatments previously used for eucalyptus. Rate Maize top composition lAA P P Ca Mg K Cu Fe Mn Zn kg/ha % Check 0 0 0.143 .42 0.50 0.74 5 65 39 27 lAA 0.031 0 0.140 0.45 0.45 0.70 5 57 40 27 0.062 0 0.145 0.41 0.47 0.71 5 70 43 32 0.124 0 0.138 0.44 0.47 0.57 5 60 46 25 Powdered CSP 0 28 0.161 0.53 0.50 0. 70 6 55 44 29 0 56 0.165 0.45 0.54 0.60 5 57 44 27 0 112 0.193 0.46 0.47 0.67 5 47 40 25 Pelletized CSP 0 28 0.153 0.55 0.50 0.82 5 67 39 32 0 56 0.202 0.71 0.54 0.48 5 50 46 26 0 112 0.205 0.65 0.45 0.66 5 55 52 24 Pelletized CSP with ]AA 0.031 28 0.174 0.63 0.51 0.88 5 67 43 33 0.062 56 0.200 0.61 0.57 0.65 6 80 47 30 0.124 112 0.220 0.43 0.50 0.81 5 60 42 27

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Table 84. lb 7 Mean analysis of maize tops sampled from 0to 15-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus . Rate lAA P Maize top composition P Ca Mg K Cu Fe Mn Zn — kg/ha — % Check 0 0 0.076 0.45 0.20 3.09 6 73 35 23 lAA 0.031 0 0.091 0.50 0.23 3.77 7 50 55 40 0.062 0 0.083 0.44 0.19 4.23 7 50 55 34 0.124 0 0.080 0.37 0.18 3.70 6 37 34 33 Powdered CSP 0 28 0.082 0.45 0.19 2.81 6 53 54 28 0 56 0.091 0.44 0.20 1.67 5 37 42 28 0 112 0.101 0.40 0.19 1.65 5 30 40 24 Pelletized CSP 0 28 0.090 0.43 0.18 2.79 5 57 48 26 0 56 0.098 0.57 0.15 2.10 5 33 36 23 0 112 0.097 0.47 0.16 1.09 5 67 59 21 Pelletized CSP with lAA 0.031 28 0.093 0.58 0.18 2.33 8 40 65 30 0.062 56 0.096 0.45 0.16 2.54 5 47 40 25 0.124 112 0.106 0.46 0.17 1.43 5 40 32 22

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Table &5'. Mean analysis of maize tops sampled from 15to 30-cm depth of undisturbed Kabete soil with treatments previously used for eucalyptus . Rate Maize top composition lAA P P Ca Mg K Cu Fe Mn Zn kg/ha % ppm Check 0 0 0.063 0.46 0.27 6.07 7 53 48 39 lAA 0.031 0 0.066 0.62 0.27 6.10 7 70 72 39 0.062 0 0.061 0.74 0.25 5.00 7 50 56 39 0.12A 0 0.064 0.98 0.27 5.27 7 57 81 50 Powdered CSP 0 28 0.065 0.64 0.19 4.80 7 73 46 32 0 56 0.073 0.64 0.19 5.13 6 47 43 27 0 112 0.094 0.51 0.17 3.63 4 50 44 25 Pelletized CSP 0 28 0.075 0.60 0.22 4.93 5 55 56 29 0 56 0.081 0.57 0.19 3.57 5 50 62 25 0 112 0.104 0.48 0.19 3.05 4 43 45 23 Pelletized CSP with lAA 0.031 28 0.071 0.71 0.24 5.10 6 45 55 30 0.062 56 0.081 0.56 0.20 4.20 5 60 56 27 0.124 112 0.109 0.49 0.15 3.80 5 40 41 22

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169 Table 86 Means and treatment comparisons for various elements in tops of Zea mays grown on three soils having residual lAA and CSP treatments. Factor Ca Mg K Cu Fe Mn Zn Sum of squares for comparisons Treatment, kg/ha ** kk kk kk ** kk 1 1AA,L * 2 1AA,Q 3 CSP form ** kk 4 CSP,L k kk kk k kk 5 CSP,Q 6 Form x rate,L 7 Form x rate,Q 8 CSP-1AA,L ** kk kk kk k kk 9 CSP-1AA,Q 10 lAA vs CSP kk kk kk kk kk 11 CSP-IAA vs CSP+IAA k kk 12 Control vs others ** k k k k Soils ** kk kk kk kk kk kk Soils X treatments ** kk kk kk k kk 1 kk 2 3 4 ** kk 5 k k 6 7 8 ** kk 9 10 ** kk kk ** kk 11 12 Soil depths ** kk kk kk Depths X treatment k 1 k* 2 k 3 4 k 5 k 6 k 7 k 8 9 10 kk k 11 k 12 kk Soils X depths kk kk k kk kk 'k kk and denote significance at the 0.05 and 0.01 level, respectively, and the letters L and Q stand for linear and quadratic, respectively.

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170 Table 8.7.^ Mean analysis of 0to 15-cm depth of Athi soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus . lAA Rate P P extracted Extractable cations by DA method DA Ca Mg K Cu Zn Ilex ppm A ppm Check 0 0 4.4 0.53 0.055 0.020 1.0 0.6 lAA 0.031 0 3.5 0.50 0.055 0.018 1.0 0.6 0.062 0 3.5 0.61 0.070 0.024 1.3 1.1 0.124 0 2.9 0.50 0.056 0.018 1.3 1.2 Powdered CSP 0 28 5.0 0.50 0.055 0.016 1.2 1.1 0 56 15.8 0.50 0.056 0.015 0.9 0.7 0 112 43.5 0.51 0.055 0.014 1.0 0.8 Pelletized CSP 0 28 6.0 0.51 0.056 0.015 1.1 1.0 0 56 21.0 0.51 0.056 0.015 1.4 1.0 0 112 65.7 0.50 0.056 0.014 1.1 0.9 Pelletized CSP with lAA 0.031 28 8.7 0.51 0.055 0.016 1.5 1.1 0.062 56 12.9 0.51 0.054 0.015 1.5 1.0 0.124 112 64.8 0.51 0.055 0.015 1.4 1.0

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171 Table 88. Mean analysis of 15to 30growth on undisturbed soil eucalyptus. -cm depth of Athi containing prior soil sampled after treatments for maize Rate P extracted Extractable cations by DA method lAA P DA Ca Mg K Cu Zn , ,, ppm kg /ha Check to ppm 0 0 9.0 0.60 0.058 0.013 0.8 0.8 lAA 0.031 0 00 0.61 0.061 0.015 0.8 0.6 0.062 0 5.6 0.60 0.059 0.014 0.9 0.7 0.124 0 6.2 0.62 0.060 0.015 0.7 0.5 Powdered CSP 0 28 11.4 0.60 0.060 0.012 0.9 1.1 0 56 00 0.60 0.057 0.012 0.8 0.8 0 112 85.2 0.60 0.058 0.013 0.7 0.7 Pelletized CSP 0 28 24.5 0.60 0.060 0.012 0.8 0.8 0 56 23.2 0.59 0.058 0.011 0.8 0.8 0 112 64.5 0.60 0.059 0.012 0.7 0.8 Pelletized CSP with lAA 0.031 28 18.5 0.61 0.059 0.012 0.8 0.9 0.062 56 27.9 0.60 0.058 0.012 0.7 0.7 0.124 112 53.9 0.61 0.060 0.012 0.8 1.0

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17 ;^. Table 89. Mean analysis of 0to 15-cm depth of Mwea soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus . Rate P extracted Extractable cations by DA method lAA P DA Ca Mg K Cu Zn kg /ha ppm % ppm Check 0 0 440 0.78 0.129 0.008 1.0 1.1 lAA 0.031 0 473 0.78 0.124 0.008 0.8 0.8 0.062 0 464 0.80 0.120 0.008 0.8 0.8 0.124 0 453 0.78 0.125 0.008 0.9 0.9 Powdered CSP 0 28 465 0.78 0.118 0.008 1.0 1.2 0 56 494 0.78 0.122 0.008 0.7 1.0 0 112 488 0.77 0.122 0.008 1.2 1.2 Pelletized CSP 0 28 469 0.81 0.124 0.008 0.9 0.9 0 56 577 0.80 0.122 0.008 1.0 0.9 0 112 558 0.79 0.121 0.008 1.1 1.2 Pelletized CSP with lAA 0.031 28 512 0.77 0.118 0.007 0.9 0.8 0.062 56 593 0.81 0.123 0.008 0.9 0.9 0.124 112 520 0.77 0.119 0.009 1.3 1.1

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173 Table 90. Mean analysis of 15to 30-cm depth of Mwea soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus . Rate P extracted Extractable cations by DA method lAA P DA Ca Mg K Cu Zn i^g/ na ppm /o ppm Check 0 0 489 0.85 0.148 0.006 0.9 1.2 lAA 0.031 0 467 0.86 0.148 0.005 0.8 0.9 0.062 0 490 0.85 0.146 0.006 0.8 0.9 0.124 0 451 0.82 0.145 0.005 0.8 0.9 Powdered CSP 0 28 531 0.83 0.144 0.005 1.0 1.0 0 56 552 0.92 0.143 0.005 0.9 1.0 0 112 578 0.91 0.141 0.005 1.0 1.2 Pelletized CSP 0 28 531 0.84 0.144 0.005 00 o 1.0 0 56 544 0.85 0.144 0.005 0.8 0.8 0 112 549 0.82 0.146 0.005 0.8 0.9 Pelletized CSP with lAA 0.031 28 536 0.86 0.145 0.005 0.9 0.9 0.062 56 543 0.91 0.143 0.005 0.9 1.0 0.124 112 591 0.92 0.145 0.005 0.9 0.8

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174 Table ‘^l* Mean analysis of 0to 15-cm depth of Kabete soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus . Rate P extracted Extractable cations by DA method lAA P DA Ca Mg K Cu Zn 1^^/ UCI ppm /o ppm Check 0 0 7.1 0.65 0.063 0.020 0.9 5.8 lAA 0.031 0 7.1 0.64 0.058 0.015 1.0 7.0 0.062 0 6.9 0.63 0.063 0.024 0.9 5.6 0.124 0 00 0.65 0.062 0.018 0.8 6.1 Powdered CSP 0 28 9.2 0.62 0.062 0.013 0.9 5.5 0 56 13.6 0.64 0.061 0.012 0.8 5.6 0 112 22.9 0.61 0.057 0.012 1.1 6.0 Pelletized CSP 0 28 8.3 0.62 0.059 0.015 0.9 00 0 56 14.6 0.65 0.062 0.013 0.9 6.0 0 112 27.3 0.63 0.058 0.009 0.8 6.4 Pelletized CSP with lAA 0.031 28 11.8 0.65 0.063 0.015 0.8 5.9 0.062 56 13.0 0.64 0.063 0.016 0.9 7.1 0.124 112 30.0 0 . 66 0.062 0.013 0.9 6.1

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175 Table 92. Mean analysis of 15to 30-cm depth of Kabete soil sampled after maize growth on undisturbed soil containing prior treatments for eucalyptus . Rate P extracted Extractable cations by DA method lAA P DA Ca Mg K Cu Zn kg/ha ppm Check /o ppnr 0 0 1.8 0.40 0.044 0.033 1.0 4.4 lAA 0.031 0 1.9 0.40 0.042 0.030 1.0 4.6 0.062 0 1.7 0.41 0.044 0.035 1.0 5.2 0.124 0 1.4 0.40 0.043 0.035 0.9 4.3 Powdered CSP 0 28 3.0 0.39 0.044 0.021 1.2 4.9 0 56 7.1 0.41 0.044 0.015 1.2 4.6 0 112 12.6 0.39 0.043 0.011 1.2 4.9 Pelletized CSP 0 28 5.0 0.39 0.042 0.018 1.0 5.1 0 56 11.0 0.40 0.042 0.013 1.1 5.2 0 112 16.6 0.41 0.044 0.013 1.1 5.1 Pelletized CSP with lAA 0.031 28 3.2 0.40 0.044 0.021 1.0 4.4 0.062 56 4.8 0.39 0.042 0.014 1.1 5.2 0.124 112 12.8 0.40 0.042 0.011 1.1 6.1

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176 Table 9i-Means and treatment comparisons for various elements extracted by DA reagent from three soils with residual lAA and CSP treatments, sampled after Zea mays harvest. Factor Ca Mg K Cu Zn — Sum of 1 sfiuaros for comparisons — Trca tiiiLMit coii]£ar 1 son 1 'lAA.’ir ** ** kk kk 2 1AA,Q ** ** kk 3 CSP form h CSP,L ** kk 5 CSP,Q 6 Form x rate,L 7 Form x rate.Q * k kk 8 CSP-1AA,L 9 CSP-1AA,Q kk k 10 lAA vs CSP * ** kk 11 CSP-IAA vs CSP+IAA ** kk kk k 12 Control vs others kk kk Soils ** kk kk kk kk Soils X treatments (as above) kk kk k 1 kk 2 * kk kk 3 kk 4 kk 5 k 6 k 7 k 8 kk 9 * kk 10 * kk kk 11 kk kk 12 kk kk Depths *k kk kk Depths X treatments (as 1 above) ** kk k ** 2 ** kk kk 3 ** k 4 5 kk 6 kk 7 8 k 9 kk 10 * kk kk 11 kk ioils X depths ** kk kk kk kk kk * if-k and denote significance at the 0.05 and 0.01 level, respectively, and the letters L and Q stand for linear and quadratic, respectively.

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177 Table 94. Mean height of maize grown on 0soil treated with indole acetic superphosphate sources at three • to 15-cm acid and rates. depth of Athi three concentrated Rate Height Weeks since emergence lAA P 2 4 6 — kg/ha — cin Check 0 0 40.0 66 . 1 82.6 lAA 0.031 0 35.1 60.1 75.7 0.062 0 35.1 61.2 74.9 0.124 0 37.4 61.6 76.9 Powdered CSP 0 28 45.9 81.8 105.3 0 56 43.3 84.2 108.6 0 112 45.4 87.8 113.3 Pelletized CSP 0 28 45.8 87.8 110.6 0 56 38.1 85.0 108.4 0 112 44.9 93.1 119.8 Pelletized CSP with lAA 0.031 28 48.0 87.9 113.4 0.062 56 41.4 83.3 108.0 0.124 112 40.6 85.2 108.2

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178 Table 95. Mean height of maize grown on 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Height Rate Weeks since emergence lAA P 2 4 6 Kg / na L.11I Check 0 0 37.4 85.2 117.3 0.031 0 44.7 93.0 127.6 0.062 0 44.9 89.3 120.6 0.124 0 45.1 88.3 117.9 Powdered CSP 0 28 45.9 100.3 130.8 0 56 47.7 99.8 132.8 0 112 54.8 112.3 140.2 Pelletized CSP 0 28 46.0 100.0 132.6 0 56 41.8 100.9 130.8 0 112 53.2 102.0 128.5 Pelletized CSP with lAA 0.031 28 50.9 97.9 129.7 0.062 56 50.8 107.0 137.3 0.124 112 47.2 105.2 134.4

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179 Table 9bMean dry matter yield of maize tops and roots from maize grown on 0to 15-cm depth of Athi and Kabete soils treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate lAA P Dry matter yield of maize Tops Athi (cm) 0-15 Kabete (cm) 0-15 Roots Athi (cm) 0-15 Kabete (cm) 0-15 Ucl Check 0 0 5.94 18.43 2.34 3.15 lAA 0.031 0 4.18 25.41 2.01 4.59 0.062 0 4.65 25.11 2.14 4.88 0.124 0 4.18 21.45 2.31 4.33 Powdered CSP 0 28 17.75 33.58 5.64 6.44 0 56 19.97 35.26 5.64 6.04 0 112 20.03 44.74 4.97 6.91 Pelletized CSP 0 28 20.13 30.34 5.34 5.15 0 56 22.84 38.56 5.32 6.87 0 112 23.79 42.43 5.30 6.43 Pelletized CSP with lAA 0.031 28 22.59 30,98 6.32 5.23 0.062 56 23.20 38.57 6.54 6.00 0.124 112 23.29 40.42 6.19 6.66

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180 Table 97. Mean analysis of maize tops sampled from 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate Maize top composition lAA P P Ca Mg K Cu Fe Mn Zn — kg/ha — % ppm Check 0 0 0.068 0.88 0.23 3.47 8 80 79 9 lAA 0.031 0 0.074 0.91 0.24 4.17 9 77 176 16 0.062 0 0.070 0.91 0.25 3.97 9 80 163 14 0.124 0 0.074 0.93 0.22 4.17 8 70 160 16 Powdered CSP 0 28 0.102 0.52 0.19 1.16 5 70 76 8 0 56 0.148 0.47 0.20 1.01 4 77 79 8 0 112 0.254 0.48 0.22 1.00 5 133 94 11 Pelletized CSP 0 28 0.121 0.50 0.21 1.12 5 90 84 8 0 56 0.156 0.42 0.18 0.94 5 120 96 9 0 112 0.236 0.42 0.18 0.78 4 70 88 9 Pelletized CSP with lAA 0.031 28 0.104 0.42 0.16 0.94 7 107 64 8 0.062 56 0.155 0.44 0.19 0.85 4 90 77 8 0.124 112 0.234 0.41 0.17 0.81 3 83 75 9

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181 Table 98. Mean analysis of maize tops sampled from 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate l.\A P Mai ze top compositi on P Ca Mg K Cu Fe Mn Zn kg/ha Check 0 0 0.105 0.76 0.28 2.73 lAA 0.031 0 0,088 0.62 0.26 2.00 0.062 0 0.097 0.60 0.27 2.13 0.124 0 0.101 0.69 0.28 2.16 Powdered CSP 0 28 0.104 0.51 0.27 1.57 0 56 0.121 0.46 0.28 1.10 0 112 0.141 0.36 0.25 0.88 Pelletized CSP 0 28 0.101 0.50 0.26 1.41 0 56 0.128 0.43 0.25 0.86 0 112 0.163 0.37 0.25 1.01 Pelletized CSP with 0.031 28 0.101 0.47 0.25 1.41 0.062 56 0.116 0.43 0.29 1.12 0.124 112 0.164 0.39 0,28 6 6 7 6 7 5 6 5 5 \ 5 6 6 ppm 110 133 88 77 101 59 67 89 59 97 97 75 47 112 42 67 157 51 47 137 42 113 177 54 60 120 43 117 130 45 90 197 54 67 177 51 53 114 38 1.01

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18 ^ Table 99. Significant factors of the analysis of variances for maize tops responses to two soils treated with lAA and CSP. Factor D.F. Ca Response Mg K Cu Fe Mn Zn bum or squares Comparisons (C) 12 ** ** ** ** kk 1 1 k 2 1 3 1 4 1 ** 5 1 * 6 1 7 1 8 1 * 9 1 ** 10 1 ** ** ** kk 11 1 ** * ** ** 12 1 ** * kk Soils(S) 1 ** ** ** ** kk SXC 12 ** * ** k* k* kk 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 ** k 9 1 k-k 10 1 ** * *k ** 11 1 ** ** ** *k 12 1 kk and denote significance at the 0.05 and 0.01 level, respectively, where the error term has 52 degrees of freedom (D.F.).

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183 Table 100. Mean analysis of maize leaves sampled from maize grown on the 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate P Ca Maize ; Leaf composition Fe Mn Zn lAA P Mg K Cu ^ l^ Of Kg/ lid /o ppmChock 0 0 0.067 0.78 0.17 0.58 27 267 50 33 lAA 0.031 0 0.065 0.85 0.18 0.93 40 200 83 37 0.062 0 0.061 0.86 0.20 1.08 47 200 90 37 0.12A 0 0.071 0.80 0.20 1.06 43 267 87 40 Powdered CSP 0 28 0.073 0.73 0.24 0.90 30 500 93 30 0 56 0.105 0.61 0.17 0.93 27 133 80 30 0 112 0.172 0.66 0.21 0.86 40 500 153 33 Pelletized CSP 0 28 0.081 0.67 0.20 0.83 30 167 80 33 0 56 0.112 0.61 0.15 0.93 20 200 83 37 0 112 0.128 0.51 0.13 0.71 30 167 103 50 Pelletized CSP with lAA 0.031 28 0.078 0.72 0.17 0.83 33 333 77 30 0.062 56 0.118 0.54 0.14 0.82 23 167 77 33 0.124 112 0.114 0.58 0.12 0.61 30 200 80 43

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184 Table 101. Mean analysis of maize leaves sampled from maize grown on the 0to 15-cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate P Maize leaf composition Fe Mn Zn lAA P Ca Mg K Cu 1 / 1_ ^ a/ 1^6/ ua /o ppm Check 0 0 0.077 0.82 0.25 1.22 33 233 137 100 lAA 0.031 0 0.056 0.86 0.29 1.13 33 233 137 90 0.062 0 0.068 0.85 0.28 1.08 27 200 110 77 0.124 0 0.085 0.90 0.34 1.23 30 233 103 80 Powdered CSP 0 28 0.062 0.75 0.27 0.96 27 300 113 80 0 56 0.086 0.71 0.29 1.02 30 200 170 70 0 112 0.116 0.80 0.35 0.82 27 133 137 57 Pelletized CSP 0 28 0.082 0.76 0.30 0.90 23 167 197 83 0 56 0.110 0.64 0.27 0.94 27 367 130 57 0 112 0.168 0 . 66 0.29 0.83 23 167 117 63 Pelletized CSP with lAA 0.031 28 0.070 0.88 0.27 1.07 33 433 210 70 0.062 56 0.088 0.77 0.33 0.88 30 167 170 80 0.124 112 0.118 0.73 0.31 0.82 27 200 120 63

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Table 102 Significant factors of the analysis of variance of maize leaf responses to two soils treated with lAA and CSP. Factor D.F. Ca Mg Response K Cu Fe Mn Zn Sum of squares Comparisons (C) 12 * * * 1 1 2 1 3 1 * * k 1 5 1 6 1 * * 7 1 ** 8 1 * 9 1 * 10 1 ** k -k* 11 1 k 12 1 Soils(S) 1 kk kk k kk kk SXC 12 i k k 1 1 2 1 3 1 k 4 1 * k k 5 1 k k 6 1 7 1 k 8 1 k 9 1 10 1 * k 11 1 * k k k 12 1 k •k kk and denote significance at the 0. 05 and 0.01 probability level, respectively , where the error term 1 has 52 degrees of freedom (D.F.).

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186 Table 103. Mean analysis of maize roots sampled from maize grown on the 0to 15-cm depth of Athi soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate Maize root composition lAA P P Ca Mg K Cu Fe Mn Zn Kg/na 7o ppm Check 0 0 0.030 0.36 0.12 0.21 8 2667 297 31 lAA 0.031 0 0.026 0.35 0.13 0.13 9 3100 623 21 0.062 0 0.025 0.39 0.13 0.13 9 3533 567 26 0.124 0 0.027 0.49 0.16 0.13 13 4967 877 29 Powdered CSP 0 28 0.049 0.31 0.12 0.29 12 3867 653 24 0 56 0.062 0.32 0.12 0.24 12 4267 857 27 0 112 0.087 0.26 0.10 0.25 10 2033 540 18 Pelletized CSP 0 28 0.044 0.25 0.12 0.23 9 2567 537 17 0 56 0.061 0.24 0.11 0.23 8 2233 453 17 0 112 0.102 0.26 0.12 0.23 Pelletized CSP with 8 lAA 2267 410 19 0.031 28 0.044 0.27 0.13 0.25 14 2700 510 21 0.062 56 0.063 0.25 0.10 0.22 15 3300 510 25 0.124 112 0.116 0.24 0.11 0.28 12 3000 277 23

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187 Table 104. Mean analysis of maize roots sampled from maize grown on the 0~ to 15~cm depth of Kabete soil treated with indole acetic acid and three concentrated superphosphate sources at three rates. Hate P Ca Maize root coni|K)Hltlon Fe Mn Zn lAA P Mg K Cu /o ppm Check 0 0 0.052 0.39 0.13 0.49 12 1030 357 86 lAA 0.031 0 0.054 0.39 0.21 0.68 12 940 530 81 0.062 0 0.055 0.43 0.21 0.54 13 1367 517 85 0.124 0 0.059 0.38 0.19 0.62 10 1193 373 97 Powdered CSP 0 28 0.064 0.41 0.20 0.52 10 920 463 67 0 56 0.074 0.38 0.21 0.56 10 683 643 64 0 112 0.090 0.31 0.13 0.50 8 757 510 52 Pelletized CSP 0 28 0.071 0.40 0.16 0.63 10 740 700 63 0 56 0.080 0.36 0.17 0.42 9 780 427 54 0 112 0.095 0.32 0.16 0.49 8 607 397 48 Pelletized CSP with lAA 0.031 28 0.070 0.48 0.16 0.45 9 727 683 51 0.062 56 0.075 0.41 0.19 0.49 10 1013 710 60 0.124 112 0.106 0.38 0.19 0.60 9 743 537 58

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Tablel05 Significant factors of the analysis of variance of maize root responses to two soils treated with lAA and CSP. Factor D.F. Ca Mg Response K Cu Fe Mn Zn oLuu UL aquares Comparisons (C) 12 ** kk k kk k 1 1 kk 2 1 3 1 k kk k 4 1 k k kk 5 1 k 6 1 k kk 7 1 k k 8 1 k 9 1 k 10 1 kk kk k kk kk 11 1 k k 12 1 k kk kk Soils(S) 1 kk kk kk kk SXC 12 kk kk kk 1 1 kk kk kk k 2 1 k 3 1 kk 4 1 kk 5 1 kk 6 1 kk 7 1 kk 8 1 9 1 10 1 kk kk kk kk 11 1 kk kk kk 12 1 k kk kk kk * A* and denote significance at the 0,05 and 0.01 level, respectively, where the error term has 52 degrees of freedom (D.F.).

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189 Table 106. Mean analysis of 0to 15-cm depth of Athi soil sampled after maize growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate P extracted lAA P da Extractable cations by DA method Ca Mg K Cu Zn kg/ha ppm % ppm Check 0 0 4.8 0.54 0.060 0.017 0.8 2.7 lAA 0.031 0 4.7 0.56 0.061 0.017 0.9 2.2 0.062 0 4.3 0.55 0.061 0.017 0.9 2.3 0.124 0 5.9 0.54 0.062 0.018 0.9 2.1 Powdered CSP 0 28 8.3 0.52 0.058 0.012 0.8 1.8 0 56 37.8 0.53 0.060 0.011 0.7 1.9 0 112 49.8 0.54 0.060 0.012 0.7 2.1 Pelletized CSP 0 28 7.6 0.54 0.060 0.011 0.7 2.1 0 56 36.4 0.53 0.061 0.012 0.7 2.0 0 112 80.8 0.55 0.060 0.011 0.7 2.0 Pelletized CSP with lAA 0.031 28 18.9 0.53 0.059 0.012 0.7 2.4 0.062 56 30.3 0.54 0.058 0.012 0.8 2.0 0.124 112 46.5 0.52 0.057 0.011 0.6 2.2

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190 Table 107. Mean analysis of 0to 15-cm depth of Kabete soil after maize growth treated with indole acetic acid and three concentrated superphosphate sources at three rates. Rate P extracted Extractable cations by DA method lAA P DA Ca Mg K Cu Zn o/ kg/ha ppm /o Check 0 0 8.9 0.68 0.067 0.020 0.8 52 lAA 0.031 0 7.9 0.72 0.073 0.020 0.8 52 0.062 0 8.7 0.72 0.071 0.014 0.7 50 0.124 0 7.7 0.68 0 . 066 0.014 0.8 51 Powdered CSP 0 28 13.3 0.68 0.006 0.011 0.9 52 0 56 20.7 0.68 0.067 0.012 0.8 52 0 112 47.3 0.70 0.066 0.011 0.8 51 Pelletized CSP 0 28 14.3 0.69 0.068 0.018 0.8 52 0 56 24.0 0.69 0.065 0.010 0.7 48 0 112 85.1 0.70 0.064 0.010 0. 7 50 Pelletized CSP with lAA 0.031 28 15.5 0.69 0.067 0.020 0.8 50 0.062 56 22.8 0.70 0.068 0.012 0.8 50 0.124 112 52.2 0.68 0.062 0.011 0.7 46

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191 Table 108. Significant factors of the analysis of variance for eucalypt tops in response to three soils treated with lAA and CSP. Factor D.F. Ca Mg K Cu Response Fe Mn Zn Sum of AA Comparison (C) 12 ** ** AA squares A AA 1 1 2 1 3 1 AA 4 1 5 1 6 1 * AA 7 1 * 8 1 * * A 9 1 10 1 ** ** AA ic:k A AA 11 1 * ** AA AA A 12 1 A AA A Soils (S) 2 ** AA AA AA AA AA SXC 12 ** A* AA ** A A A A 1 A 2 3 A 4 A 5 ** 6 7 8 9 10 ** AA AA A AA AA 11 AA AA AA A 12 AA AA and denote significance at the 0'05 and 0-01 level, respectively, where error term has 156 degrees of freedom (D.F.).

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LITERATURE CITED Adams, W. E. , A. W. White, R. A, McCreery, and R. N. Dawson, 1967. Coastal bermudagrass forage production and chemical composition as influenced by potassium source, rate and frequency of application. Agron. J. 59:247-250. Allan, A. Y. 1974. The development of improved agronomic practices for maize production in Kenya under favorable rainfall conditions. p. 486-494. Iji Proceedings of the first FAO/SIDA seminar on improvement and production of field food crops for plant scientists from Africa and the Near East. Rome, Italy; FAO and Natn. Agric. Res. Stn. Kltale, Kenya. Allen, S. E. , and D. A. Mays. 1971. Sulfur-coated fertilizers for controlled release: agronomic evaluation. J. Agric. Food Chem. 19:809-812. Bailey, L. D. , E. D. Spratt, D. W. L. Read, F. G. Warder, and W. S. Ferguson. 1977. Residual effects of phosphorus fertilizer. II. For wheat and flax grown on chernozemic soils in Manitoba. Can. J. Soil Sci. 57:263-270. Barber, S. A. 1958. Relation of fertilizer placement to nutrient uptake and crop yield. I. Interaction of row phosphorus and the soil level of phosphorus. Agron. J. 50:535-539. Barber, S. A. 1965. Fall corn fertilization: Plant Food Rev. 11: No. 3, p. 9-11. Barber, S. A. 1969. Flexibility in applying phosphorus and potassium. Crops Soils 21(9): 16-17. Barber, S. A. 1974a. A program for increasing the efficiency of fertilizers. Fert. Solutions 18(2):24-25. Barber, S. A. 1974b. Influence of the plant root on ion movement in soil. p. 525-564. Hi E. W. Carson (ed.). The plant root and its environment. Univ. Press of Virginia, Charlottesville. Barret, R. L. , and L. J. Mullin. 1968. A review of introductions of forest trees in Rhodesia. Rhodesian Bull, of Forest Research No. 1. Rhodesia Forestry Commission, Salisbury. 192

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193 Bates, T. E. 1971. Response of corn to small amounts of fertilizer placed with the seed: II. Summary of 22 field trials. Agron. J. 63:369-371. Beadle, N. C. W. 1953. The edaphic factor in plant ecology, with a special note on soil phosphates. Ecology, 34:426-428. Belcher, C. R. , and J. L. Ragland. 1972. Phosphorus absorption by sod-planted corn ( Zea mays L.) from surface-applied phosphorus. Agron. J. 64:754-756. Bell, L. C. , and C. A. Black. 1970. Comparison of methods for identifying crystalline products produced by interaction of orthophosphate fertilizers with soils. Soil Sci. Soc. Am. Proc. 34:579-582. Black, C. A. 1957. Soil-Plant Relationships, p. 253. Wiley, New York. Black, C. A. (ed.). 1965. Methods of soil analysis, part 2. Agronomy No. 9. Am. Soc. of Agron., Inc., Publ. Madison, Wisconsin, U.S.A. Blakely, W. F. 1955. A key to the Eucalypts, second edition. Forestry and Timber Bureau, Canberra, Australia. Bowman, R. A., S. R. Olsen, and F. S. Watanabe. 1978. Greenhouse evaluation of residual phosphate by four phosphorus methods in neutral and calcareous soils. Soil Sci. Soc. Am. J. 42:451-454. Chakravarti, S. N. , and 0. Talibudeen. 1962. Phosphate equilibria in acid soils. J. Soil Sci. 13:231-240. Chang, S. C. , and W. K. Chu. 1961. Fate of soluble phosphate applied to soils. J. Soil Sci. 12:286-293. Chang, S. C. , and M. L. Jackson. 1957. Fractionation of soil phosphorus. Soil Sci. 84:133-144. Chang, S. C. , and M. L. Jackson. 1958. Soil phosphorus fractions in some representative soils. J. Soil Sci. 9:109-119. Chang, S. C. , and A. S. R. Juo. 1963. Available phosphorus in relation to forms of phosphorus in soils. Soil Sci. 95:91-96. Chien, S. H. , and W. R. Clayton. 1980. Application of Elovich equation to the kinetics of phosphate release and sorption in soils. Soil Sci. Soc. Am. J. 44:265-268.

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194 Chien, S. H. , W. R. Clayton, and G. H. McClellan. 1980. Kinetics of dissolution of phosphate rocks in soils. Soil Sci. Soc. Am. J. 44:260-264. Chippendale, G. M. 1973. Eucalypts of the Western Australian goldfields (and the adjacent wheat belt) . Australian Govern. Publ. Service, Canberra. Cihacek, L. J. , D. L. Mulvaney, R. A. Olson, L. F. Welch, and R. A. Wiese. 1974. Phosphate placement for corn in chisel and mold-board plowing systems. Agron. J. 66:665-668. Cole, C. V., and M. L. Jackson. 1950. Colloidal dihydroxy dihydrogen phosphates of aluminum and iron with crystalline character established by electron and X-ray diffraction. J. Phys. & Colloid. Chem. 54:128-142. Cole, E. V., and M. L. Jackson. 1951. Solubility equilibrium constant of dihydroxy aluminum dihydrogen phosphate relating to a mechanism of phosphate fixation in soils. Soil Sci. Soc. Am. Proc. 15:84-89. Cooper, P. J. M. 1979. The association between altitude, environmental variables, maize growth and yields in Kenya. J. Agr. Sci. 93:635-649. Creamer, F. L. , and Fox, R. H. 1980. The toxicity of banded urea or diammonium phosphate to corn as influenced by soil temperature, moisture, and pH. Soil Sci. Soc. Am. J. 44:296-300. Darville, A. G. , C. J. Smith, and M. A. Hall. 1979. Auxin induced proton release, cell wall structure and elongation growth: A hypothesis. p. 275-282. ^ Dep. of Bot. and microbial. Univ. Coll, of Wales, Abery-stwy th, Dyfed SY 23 3DA, U.K. Davies, P. J. , J. A. Doro, and A. W. Tarbox. 1976. The movement and physiological effect of indole acetic acid following point applications to root tips of Zea mays L. Physiol. Plantarum 36:333-337. De Datta, S. K. , R. L. Fox, and C. D. Sharman. 1963. Availability of fertilizer phosphorus in Latosols of Hawaii. Agron. J. 55:311-313. de Mooy, C. J., J. L. Young, and J. D. Kaap. 1973. Comparative response of soybeans and corn to phosphorus and potassium. Agron. J. 65:851-855.

PAGE 211

Edwards, K. L. , and M. H. Goldsmith. 1980. pH-dependent accumulation of indole acetic acid by corn coleoptile sections. Planta 147:457-466. Edwards, K. L. , and T. K. Scott. 1974. Growth responses and their characteristics in corn root and coleoptile segments. Dissertation Abs. Inter. 635:2587-2588. Edwards, K. L. , and T. K. Scott. 1977. Rapid-growth responses of corn root segments: effect of auxin on elongation. Planta 135:1-5. Engelstad, 0. 1\, and G. I,. Tcrman. 1980. Ap.ronnmic effectiveness of phosphate fertilizers, p. 311-332. F. E. Khasawneh, K. C. Sample, and F. .1. Kamprath (oils.). The role of phosphorus in agriculture. Am. Soc. of Agron. , Crop Sci. Soc. of Am., Soil Sci. Soc. of Am., Madison, Wisconsin U.S.A. Enwezor, W. 0. 1977. Soil testing for phosphorus in some Nigerian soils. 2. Predicting responses to phosphate applications for soils of southeastern Nigeria. Soil Sci. 123:111-116. Evans, M. L. , T. J. Mulkey, and M. J. Vesper. 1980. Auxin action on proton influx in corn roots and its correlation with growth. Planta 148:510-512. FAO Forestry Development Paper No. 19., 1974. Food and Agri. Organization of the United Nations, Rome. Feldman, L. J. 1980. Auxin biosynthesis and metabolism in isolated roots of Zea mays L. Physiol. Plantarum 49:145-150. Fiskell, J. G. A., R. S. Mansell, H. M. Selim, and F. G. Martin. 1979. Kinetic behavior of phosphate sorption by acid, sandy soil. J. Environ. Qual. 8:579-584. Gctlif n-Jones , G. II. 1949. GoJonlal soil. Ly|ies: systematic soil classification and nomenclature. Proceedings of the first commonwealth conference on tropical and sub-tropical soils. Comm. Bur. Soil Sci., Harpenden, England. Tech. Comm. No. 46, p. 92. Ghani, M. 0., and M. A. Islam. 1946. Phosphate fixation in acid soils and its mechanism. Soil Sci. 62:293-306. Gilliam, J. W. , and E. C. Sample. 1968. Hydrolysis of pyrophosphate in soils: pH and biological effects. Soil Sci. 106:352-357. Goring, H. , V. V. Palevoy, R. Stahlberg, and G. Sturape. 1979. Depolarization of transmembrane potential of corn and wheat coleoptiles under reduced water potential and after lAA application. Plant and Cell Physiol. 20:649-656.

PAGE 212

196 Groulez, J. 1967. Introduction d'Eucalyptus au Congo Brazzaville. Proceedings of the World Symposium on Man-made forests and their Industrial Importance, 3:1447. Rome, FAO. Hall, P. L. , and R. S. Bandurski. 1978. Movement of indole-3-acetic acid and tryptophanderived indole-3-acetic acid from the endosperm to the shoot of Zea mays L. Plant Physiol. 61:425-429 Hall, N., R. D. Johnston, G. M. Cheppendale. 1970. Forest trees of Australia. Australian Government Publ. Service, Canberra. Hanley, K. 1962. Soil phosphorus forms and their availability to plants. Irish J. Agr. Res. 1:192-193. Harter, R. 1969. Phosphorus adsorption sites in soils. Soil Sci. Soc. Am. Proc. 33:630-632. Haschke, H. P., and V. Luttge. 1978. Auxin action on K‘*'-H’^ex change and growth, ^ ‘‘COa-f ixation and malate accumulation in Avena coleoptile segments, p. 243-248. ^n Institute fur Botanik, Technishe Hochschule, D-6100. Darmstaat, Ger . Fed. Republic; Field Crops Abs. (1979) 4238. Haseman, J. F. , E. H. Brown, and C. D. Whitt. 1950. Some reactions of phosphate with clays and hydrous oxides of iron and aluminum. Soil Sci. 70:257-271. Haseman, J. F. , J. R. Lehr, and J. P. Smith. 1951. Mineralogical character of some iron and aluminum phosphates containing potassium and ammonium. Soil Sci. Soc. Am. Proc. 15:76-84. Hashimoto, Isao, J. D. Hughes, and 0. D. Philen, Jr. 1969. Reactions of triammonium pyrophosphate with soils and soil minerals. Soil Sci. Soc. Am. Proc. 33:401-405. Hawkins, R. H. , and G. G. Kunze. 1965. Phosphate fractions in some Texas Grumusols and their relation to soil weathering and available phosphorus. Soil Sci. Soc. Am. Proc. 29:650-656. Hira, G. S., and N. T. Singh. 1978. Prediction of phosphorus diffusion from fertilizer source. Soil Sci. Soc. Am» J 42 :561-565 Jacobs, M. , and P. M. Ray. 1976. Rapid auxin-induced decrease in free space pH and its relationship to auxin-induced growth in maize and pea. Plant Physiol 58:203-209. Johnston, A. E. , R. G. Warren, and A. Penny. 1969. The value of residues from long term manuring at Rothamsted and Woburn. IV. The value to arable crops of residues accumulated from superphosphate. Rothamsted Rep. for 1969: part 2:69-90. Harpenden, Herts, U.K.

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197 Kaila, A. 1965. The fate of water-soluble phosphate applied to some mineral soils. J. Sci. Agr. Soc. Finland (Maataloust. Aikakavsk.) 37:104-115. Kamprath, E. J. 1967. Residual effect of large applications of phosphorus on high fixing soils. Agron. J. 59:25-27. Karakis, K. D. 1974. [Significance of trace elements in enzymatic biosynthesis of lAA. ] Referativnyi Zhurmal Biologiya 1 4G324; Field Crops Abs. (1976) 29:3675. Khasawneh, F. E., I. Kdshimoto, and E. C. Sample. 1979. Reactions of ammonium orthoand poly-phosphate fertilizers in soil: II. Hydrolysis and Reactions with soil. Soil Sci. Soc. Am. J. 43:52-58. Khasavmeh, F. E., E. C. Sample, and I. Hashimoto. 1974. Reactions of ammonium orthoand poly-phosphate fertilizers in soil: I. Mobility of phosphorus. Soil Sci. Soc. Am. Proc. 38:446-451. Kittrick, J. A., and M. L. Jackson. 1955. Rate of phosphate reaction with soil minerals and electron microscope observations on the reaction mechanism. Soil Sci. Soc. Am. Proc. 19:292-295. Kittrick, J. A., and M. L. Jackson. 1956. Electron-microscope observations of the reaction of phosphate with minerals, leading to a unified theory of phosphate fixation in soils. J. Soil Sci. 7:81-89. Kobyl'skaya, G. V., V. V. Polevoi, and T. V. Voloshina. 1976. [Effect of lAA and Mn^"^ on activity and isoenzyme composition of malate dehydrogenase.]. Referativnyi Zhurnal, Biologiya 1(1978) 2G161; Field Crops Abs. (1979) 32:2206. Larsen, S. 1967. Soil phosphorus. Adv. Agron. 19:151-210. Lathwell, D. J., J. T. Cope, Jr., and J. R. Webb. 1960. Liquid fertilizers as sources of phosphorus for field crops. Agron. J. 52:251-254. Lavery, J. C. , and E. 0. McLean. 1961. Factors affecting yields and uptake of phosphorus by different crops: III. Soil Sci. 91:166-171. Lee, T. T. 1980. Effects of phenolic substances on metabolism of exogenous indole3-acetic acid in maize stems. Physiol. Plantarum 50:107-112.

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198 Lehr, J. R. , and W. E. Brown. 1958. Calcium phosphate fertilizers II. A petrographic study of their alteration in soils. Soil Sci. Soc. Am. Proc. 22:29-32. Lehr, J. R. , W. E. Brown, and E. H. Brown. 1959. Chemcial behavior of monocalcium phosphate monohydrate in soils. Soil Sci. Soc. Am. Proc. 23:3-7. Lindsav. W. L. . A. W. Frazier, and H. F. Stenhenson. 1962. Identification of reaction nroducts from nhosohate fertilizers in soils. Soil Sci. Soc. Am. Proc. 26:446-452. Lindsay. W. L. . M. Peech. and J. S. Clark. 1959. Solubility criteria for the existence of variscite in soils. Soil Sci. Soc. Am. Proc. 23:12-18. Lindsay, W. L. , and H. F. Stephenson. 1959. Nature of the reactions of monocalcium phosphate monohydrate in soils : IV. Repeated reactions with metastable triple-point solution. Soil Sci. Soc. Am. Proc. 23:440-445. Lindsay, W. L., and P. L. G. Vlek. 1977. Phosphate minerals. p. 639-672. ^n J. B. Dixon and S. B. Weed (ed.). Minerals in soil environments. Soil Sci. Soc. Am., Inc., Madison, Wis. Martin, H. V., M. C. Elliott, E. Wangermann, and P. E. Pilet. 1978 Auxin gradient along the root of the maize seedling. Planta 141:179-181. McLean, E. 0., and T. J. Logan. 1970. Sources of phosphorus for plants grown in soils with differing phosphorus fixation tendensies. Soil Sci. Soc. Am. Proc. 34:907-911. McLean, E. 0., R. W. Wheeler, and J. D. Watson. 1965. Partially acidulated rock phosphate as a source of phosphorus to plants: II. Growth chamber and field corn studies. Soil Sci. Soc. Am. Proc. 29:625-628. Meelu, 0. P., D. S. Rana, K. N. Sharma, and S. Raghubir. 1977. Comparative efficiency of different complex phosphatic fertilizers. J. Indian Soc. Soil Sci. 25:374-378. Mekaru, T. , and G. Uehara. 1972. Anion adsorption in ferruginous tropical soils. Soil Sci. Soc. Am. Proc. 36:296-300. Moreno, E. C. , W. E. Brown, and G. Osborn. 1960a. Solubility of dicalcium phosphate dihydrate in aqueous systems. Soil Sci. Soc. Am. Proc. 24:94-98.

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199 Moreno, E. C. , W. E. Brown, and G. Osborn. 1960b. Stability of dicalcium phosphate dihydrate in aqueous solutions and solubility of octocalcium phosphate. Soil Sci. Soc. Am. Proc. 24:99-102. Mortvedt, J. J. , and G. L. Terman. 1978. Nutrient effectiveness in relation to rates applied for pot experiments: II. Phosphorus sources. Soil Sci. Soc. Am. J. 42:302-306. Moschler, W. W. , and D. C. Martens. 1975. Nitrogen, phosphorus, and potassium requirements in notillage and conventionally tilled corn. Agron. J. 39:886-891. Mousdale, D. M. A., D. N. Butcher, and R. G. Powell. 1980. Spectrophotof luorimetric methods of determining indole3-acetic acid. p. 27-39. ^ ARC Unit of Developmental Bot; Cambridge CB3 ODY, U.K.; Field Crops Abs. (1980) 33:9610. Murphy, J., and J. P. Riley. 1962. A modified single solution method for the determination of phosphate in natural waters. Anal. Chira. Acta 27:31-36. Naqvi, S. M. 1976. Auxin in Zea mays L. coleoptile segments: saturation of absorption and transport at various concentrations. Pakistan J. Bot. 8:47-52; Field Crops Abs. (1977) 30:3245. Naqvi, S. M. , and S. A. Gordon. 1978. Temperature and auxin transport in Zea mays L. coleoptiles. Pakistan J. Bot. 10:113-118; Field Crops Abs. (1980) 33:6023. Nelles, A. 1977. [Estimation of the relative sodium permeability of maize coleoptile cells by electrophysiological measurements.] Biochemie und Physiologie der Pflanzen 171:55-62. Nicholaides, J. J., III., J. G. A. Fiskell, and F. G. Martin. 1979. Corn response to S-coated and non-coated superphosphates and residual effects. Agron. J. 71:1021-1026. Nowacki, J., and R. S. Bandurski. 1980. Myo-inositol esters of indole-3-acetic acid as seed auxin precursors of Zea mays L. Plant Physiol. 65:422-427. Nowakowski, W. 1979. [The effect of lAA on lAA oxidase activity in scediings of winter wheat and maize grown under conditions of osmotic stress.] Acta agrobotanica 32:101-107; Field Crops Abs. (1981) 34:1625. Nye, P. II. 1968. The use of exchange Isotherms to determine diffusion coefficients in soil. int. Congr. Soli Sci., Trans. 9th (Adelaide) 1:117-126.

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200 Oliver, S. , and S, A. Barber. 1966, An evaluation of mechanisms governing the supply of Ca, Mg, K, and Na to soybean roots ( Glycine max ) . Soil Sci. Soc. Am. Proc. 30:82-86. Olsen, S. R. , C. V. Cole, F. S. Watanabe, and L. A. Dean. 1954. Estimation of available phosphorus in soils by extraction with sodium bicarbonate. USDA Circ. 939. Olsen, S. R. , and F. S. Watanabe. 1957. A method to determine a phosphorus adsorption maximum of soil as measured by the Langmuir iostherm. Soil Sci. Soc. Am. Proc. 21:144-149. Olsen, S. R. , F. S. Watanabe, and R. A. Bowman, 1978. Evaluation of soil phosphate residues by plant uptake and extractable phosphorus, p. 43-75. In Proc. of Soils and Crops Workshop, Pub. No. 390, Extension Div. , Univ. of Saskatchewan, Saskatoon, Canada. Olson, R. A., A. F. Dreier, C. A. Hoover, and H. F. Rhoades. 1962. Factors responsible for poor response of corn and grain sorghum to phosphorus fertilization: I. Soil phosphorus level and climatic factors. Soil Sci. Soc. Am. Proc. 26:571-574. Pandey, S. N. 1970. Effect of indole acetic acid and gibberellic acid on amino acids of maize ( Zea mays L.) plants grown under saline conditions. J. Sci. Res. Banaras Hindu Univ. 20:151-167; Field Crops Abs . (1976) 29:4577. Passioura, J. B. 1963. A mathematical model for the uptake of ions from the soil solution. Plant Soil 18:225-238, Patel, K. R. , C. K. Shah, and A. C. Dhar. 1978. Effect of lAA on endogenous RNA content and cell elongation. Indian J. Plant Physiol. 21:133-141. Payne, H. , and W. J. Hanna. 1965. Correlations among soil phosphorus fractions, extractable phosphorus and plant content of phosphorus. J. Agr. Food Chem. 13:322-326. Peech, M. , L. A. Dean, and J, Reed. 1947. Methods of soil analysis for soil fertility investigations. U.S. Dept. Agr. Circ. 757. Penfold, A, R. , and J. L. Willis. 1961 The Eucalypts: Botany, Cultivation, Chemistry, and Utilization Interscience Publ. , Inc. New York, Pereira, H. C, 1957. Field measurements of water use for irrigation control in Kenya coffee. J. Agric. Sci, 49:459-466.

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201 Pernet, J. J., and P. E. Pilet. 1976. indole acetic acid movement in the root cap. Planta 128:183-184. Pilet, P. E. , M. C. Elliott, and M. M. Moloney. 1979. Endogenous and exogenous auxin in the control of root growth. Planta 146:405-508. Pritchett, W. L. 1979. Properties and management of forest soils. John Wiley & Sons. New York. Prummel, J. 1956. Placement of fertilizers. Int. Congr. Soil Sci., Trans. 6th (Paris) IV:167-171. Pryor, L. D. , and L. A. S. Johnson. 1971. A classification of the eucalypts. The Australian National Univ. , Canberra. Rajan, S. S. S., and R. L. Fox. 1975. Phosphate adsorption by soils. II. Reactions in tropical acid soils. Soil Sci. Soc. Am. Proc. 39:846-851. Rasi-Caldogno , F. , R. Cerana, and M. C. Pugliarello. 1978. Effects of anaerobiosis on auxinand fusicoccin-induced growth and ion transport. Experientia 34(7) : 841-842. Read, D. W. L. , E. D. Spratt, L. D. Bailey, and F. G. Warder. 1977. Residual effects of phosphorus fertilizer. I. For wheat grown on four chernozemic soil types in Saskatchewan and Manitoba. Can. J. Soil Sci. 57:255-262. Robertson, W. K. , L. G. Thompson, Jr., and C. E. Hutton. 1966. Availability and fractionation of residual phospliorus in soils high in aluminum and iron. Soil Sci. Soc^ Am. Proc. 30:446-450. Rubenstein, B., K. D. Johnson, and D. L. Rayle. 1979. Calciumenhanced acidification in oat coleoptiles. p. 307-316. ^ Dept, of Bot., Massachusetts, Univ., Amherst, MA. Rudd, C. L. , and N. J. Barrow. 1973. The effectiveness of several methods of applying superphospliate on yield response by wheat. Aust. J. Exp. Agric. Anim. llusb. 13(63) :430-433. Rule, A. 1967. Forests of Australia. Halstead Press, Sydney. Sample, E. C. , F. E. Khasawneh, and I. llashimoLo. 1979. Reactions of ammonium orthoand poly-phospliate fertilizers in soil: III. Effects of associated cations. Soil Sci. Soc. Am. J. 43:58-65. Sartain, J. B. , H. L. Breland, and J. Nesmith. 1976. Evaluation of various nutrient extractants for Florida soils as influenced by selected soil: solution ratios and shaking times. Soil and Crop Sci. Soc. Fla. Proc. 35:183-186.

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202 Schurzmann, M. , and V. Hild. 1980. Effect of indole acetic acid, abscisic acid, root tips and coleoptile tips on growth and curvature of maize roots. Planta 150:32-36. Shipp, R. F., and R. P. Matelski. 1960. A microscopic determination of apatite and a study of pliosidioriis In some Nel)raska soil profiles. Soil Scl. Soc. Am. Proc. 24:450-452. Singh, R. N. , D. C. Martens, and S. S. Obenshain. 1966. Plant availability and form of residual phosphorus in Davidson clay loam. Soil Sci. Soc. Am. Proc. 30:617-620. Singh, T. A., G. W. Thomas, W. W. Moschler, and D. C. Martens. 1966. Phosphorus uptake by corn ( Zea mays L.) under no-tillage and conventional practices. Agron. J. 58:147-148. Smith, A. N. 1965. The supply of soluble phosphorus to the wheat plant from inorganic soil phosphorus. Plant soil 22:314-316. Sorrells, M. E., R. E. Harris, and J. H. Lonnquist. 1978. Responses of prolific and non-prolific maize to growth-regulating chemicals. Crop Sci. 18:783-787. Spratt, K.D., and fh V. McCurdy. 1966. Tlie effect of various long term soil fertility treatments on the phosphorus status of a clay chernozem. Can. J. Soil Sci. 46:29-36. Stanford, G., J. Hanway, and H. R. Meldrum. 1955. Effectiveness and recovery of initial and subsequent fertilizer applications on oats and the succeeding meadows. Agron. J. 47:25-31. Stein, W. I., J. L. Edwards, and R. W. Tinus. 1975. Outlook for containergrown seedling use in reforestation. J. For. 73:337-341. Streets, R. J. 1962. Exotic forest trees in the IJritish Commonwealth. Clarendon Press, Oxford. Susuki, A., K. Lawton, and E. C. Doll. 1963. Phosphorus uptake and soil tests as related to forms of phosphorus in some Michigan soils. Soil Sci. Soc. Am. Proc. 27:401-403. Sutton, C. D. , D. Gunary, and S. Larsen. 1966. Pyrophosphate as a source of phosphorus for plants: II. Hydrolysis and initial uptake by a barley crop. Soil Sci. 101:199-204. Sutton, C. D., and S. Larsen. 1964. Pyrophosphate as a source of phosphorus for plants. Soil Sci. 97:196-201.

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203 Taylor, R. W. , and B. G. Ellis. 1978. A mechanism of phosphate adsorption on soil and anion exchange resin surfaces. Soil Sci. Soc. Am. , J. 42:432-436. Taylor, A. W. , W. L. Lindsay, E. 0. Huffman, and E. L. Gurney. 1963. Potassium and ammonium taranakites, amorphous A1 phosphate and variscite as sources of P for plants. Soil Sci. Soc. Am. Proc. 27:148-151. Templeton, W. G., Jr., and T. H. Taylor. 1966. Yield response of a tall fescue-white clover sward to fertilization with nitrogen, phosphorus, and potassium. Agron J. 58:319-322. Terman, G. L. 1957. Variability in phosphorus rate and source experiments in relation to crop and yield levels. Agron. J. 49:271-276. Terman, G. L. , S. E. Allen, and 0. P. Engelstad. 1970. Response by paddy rice to rates and sources of applied phosphorus. Agron. J. 62:390-394. Terman, G. L. , P. M. Giordano, and N. W. Ghristensen. 1975. Corn Iiybrld yield effects on pliosphoriis , manganese, and zinc absorption. Agron. J. 67:182-184. Todor, G. K. , G. S. Ivan, and A. G. Dimitrina. 1977. [Restoration of maize plants grown in Mg-deficient medium with growth regulators.] Fiziolgiya na Rasteniyata 3:40-46. Field Crops Abs. (1979) 32:742. Trifu, M. , and T. Osvath. 1978 [Influence of the complex treatment with gamma radiation emitted from ®°Co, with trace elements and with growth substances on the phosphorus nutrition of maize.] Contributii Botanice Univ. "Babes-Bolyai , p. 277-281; Field Crops Abs. (1979) 32:6779. Triplett, G. B., Jr., and D. M. Van Doren, Jr. 1969. Nitrogen, phosphorus, and potassium fertilization for non-tilled maize. Agron. J. 61:637-639. Uriyo, A. P., B. R. Singh, and A. E. Kimambo. 1980. Evaluation of P placement methods, N carriers and NP effects on soil, maize yield and NPK in leaves. East African Agr. and For. J. 42:353-358. Vanderhoef, L. N., and W. R. Briggs. 1978. Red light inhibited mesocotyl elongation in maize seedlings. I. The auxin hypothesis. Plant Physiol. 61:534-537.

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204 Venis , M. A., and P. J. Watson. 1978. Naturally occurring modifiers of auxin-receptor interaction in corn: identification as benzoxazolinones . Planta 142:103-107. Volk, V. V., and E. 0. McLean. 1963. The fate of applied phosphorus in four Ohio soils. Soil Sci. Soc. Am. Proc. 27:53-58. Walkley, A. 1946. A critical examination of a rapid method for determining organic carbon in soils — effect of variations in digestion conditions and of inorganic soil constituents. Soil Sci. 63:251-263. Walkley, A., and 1. A. Black. 1934. An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method. Soil Sci. 37:29-38. Wangermann, E. , and L. A. Withers. 1978. Auxin transport characteristics and cellular ultra-structure of different types of parenchyma. New Phytologist 81:1-17. Webb, J. R. , Kalju Eik, and J. T. Pesek. 1961. An evaluation of phosphorus fertilizers applied broadcast on calareous soils for corn. Soil Sci. Soc. Am. Proc. 25:232-236. Webb, J. R. , and J. T. Pesek. 1958. An evaluation of phosphorus fertilizers varying in water solubility: I. Hill applications for corn. Soil Sci. Soc. Am. Proc. 22:533-538. Webb, J. R. , and J. T. Pesek. 1959. An evaluation of phosphorus fertilizers varying in water solubility: II. Broadcast applications for corn. Soil Sci. Soc. Am. Proc. 23:381-384. Welch, L. F., D. L. Mulvaney, L. V. Boone, G. E. McKibben, and J. W. Pendleton. 1966. Relative efficiency of broadcast versus banded phosphorus for corn. Agron. J. 58:283-287. Woodruff, J. R. , and E. J. Kamprath. 1965. Phosphorus adsorption as measured by the Langmuir isotherm and its relationship to phosphorus availability. Soil Sci. Soc. Am. Proc. 29:148-150. Yost, R. S. 1978. Effect of rate and placement on availability and residual value of P in an oxisol of central Brazil. Diss . Abs. Int. B:489-490. Field Crops Abs. (1981) 34:826. Yuan, T. L. , W. K. Robertson, and J. R. Neller. 1960. Forms of newly fixed phosphorus in three acid sandy soils. Soil Sci. Soc. Am. Proc. 24:447-450. Zaric, L. 1978. [Effect on temperature on the content of endogenous growth substances of tlic auxin type in maize seedlings wl tli varying resistance to low temperatures.] Arhiv Za Poljoprivredne Nauke. 31:83-112; Field Crops Abs. (1981) 34:193.

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BIOGRAPHICAL SKETCH Joseph Klpkorir A. Keter, son of James and Grace Bira, was born on November 21, 1944, at Kericho, Kenya. He attended his high schools at Kericho Secondary and Friends School Kamusinga. He graduated from the University of Nairobi In 1971 wltlv a B.Sc. in chemistry and geology. In 1972 he obtained a German scholarship to study for an M.Sc. degree in soil science in the University of Nairobi. He obtained the M.Sc. degree in soil science in February 1975 following which he was appointed a lecturer in soil science in the University of Nairobi. He taught there until August, 1977, when he was awarded an USAID scholarship to study for a Ph.D. degree in soil science (soil chemistry) at the University of Florida. He is a member of the American and International Societies of Soil Science. Joseph Keter is married to Mary Chepkemoi Keter and they have one child, Winnie Chepkirui, aged 3. 205

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. John G. A. Fiskell, chairman Professor of Soil Science I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Victor W. Carlisle Professor of Soil Science I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. A 1/ ( L\ William L. /Pritchett ^ i Professor of Soil Science

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Pejaver V. Rao Professor of Statistics I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. Donald F. Rothwell Professor of Soil Science

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I certify that I have read this study and that in my opinion it conforms to acceptable standards of scholarly presentation and is fully adequate, in scope and quality, as a dissertation for the degree of Doctor of Philosophy. August, 1981 Dean Dean, Graduate School