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 Front Cover
 Title Page
 Table of Contents
 Introduction
 Materials and methods
 Results and discussion
 Summary and conclusions
 Acknowledgement
 Literature cited
 Back Cover














Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; no. 778
Title: Soil testing as a guide to phosphorus fertilization of young pine plantations in the Coastal Plain
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00027191/00001
 Material Information
Title: Soil testing as a guide to phosphorus fertilization of young pine plantations in the Coastal Plain
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 22 p. : ill. ; 23 cm.
Language: English
Creator: Ballard, Russell
Pritchett, William L
Publisher: Agricultural Experiment Stations, Institute of Food and Agricultural Sciences
Place of Publication: Gainesville
Publication Date: 1975
 Subjects
Subject: Soils -- Testing -- Southern States   ( lcsh )
Pine -- Fertilizers -- Southern States   ( lcsh )
Phosphatic fertilizers -- Southern States   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 21-22.
Statement of Responsibility: R. Ballard and W.L. Pritchett.
General Note: Cover title.
Funding: Bulletin (University of Florida. Agricultural Experiment Station)
 Record Information
Bibliographic ID: UF00027191
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 001596991
oclc - 02452131
notis - AHM1121

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Title Page
    Table of Contents
        Table of Contents
    Introduction
        Page 1
    Materials and methods
        Page 2
        Page 3
        Page 4
    Results and discussion
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
    Summary and conclusions
        Page 19
        Page 20
    Acknowledgement
        Page 21
    Literature cited
        Page 21
        Page 22
    Back Cover
        Back Cover
Full Text



3oil Testing as a Guide to
hosphorus Fertiliztiorf of
foung Pine Planfatiha in
the Coastal Plain
R. Ballard and W. L. Pritchett


Agricultural Experiment Stations Institute of Food and Agricultural Sciences
J. W. Sites, Dean for Research University of Florida, Gainesville


fj7 (technical)


November 1975











Soil Testing as a Guide to

Phosphorus Fertilization of

Young Pine Plantations

In the Coastal Plain






R. Ballard and W. L. Pritchett

Dr. Ballard is Research Scientist, New Zealand Forest Research
Institute, Rotorua, N. W. (Formerly Graduate Assistant, University
of Florida), and Dr. Pritchett is Professor of Forest Soils, Univer-
sity of Florida Agricultural Experiment Stations, Gainesville.


This public document was promulgated at an annual cost
of $1,209.27 or 240 per copy to present correlations between
field test results and soil test methods and guides for inter-
preting test results in terms of fertilizer recommendations
for forests.







TABLE OF CONTENTS

Introduction -------..............-----..----.. 1
Materials and Methods ---... ..-- ---- ----------.... 2
Field trials -.....--....--------- --..... 2
Soil samples ........---- ......--- 2
Foliage samples --------------- 2
Tree growth and response parameters ........---------.... 3
Soil analysis ...-------....------------------ 4
Relationships between soil test values
and tree growth and response .......................---.- 5
Results and Discussion ---.--...........------..... ---...-----. 5
Relationships between soil test values
and relative heights ..-.............-------------- 5
Relationships between soil test values
and heights of unfertilized trees ... .....------------... 10
Relationships between foliar P, tree parameters,
and soil test values ........-----------------------.13
Relationships between soil test values
and P fertilizer requirements -............-----------.14
Summary and Conclusions -.......-..------.--- -..----- 19
Acknowledgments -........... --......- .... 21
Literature Cited .----- ...............--------------------21





Introduction


Approximately 740,000 acres (300,000 ha) of pines are planted
annually in the southeastern United States. Extensive fertilizer
trials in the region have shown excellent growth responses to ad-
ditions of phosphorus (P) fertilizer (14, 15, 16, 21) to young
plantations. In fact, it has been estimated that about two-thirds,
or 500,000 acres (200,000 ha), of these new plantings would bene-
fit from fertilizer applications (16). However, only about 250,000
acres (100,000 ha) of young pine have been fertilized during the
past 5 years. This relatively slow acceptance has been due, in
part, to the lack of precise diagnostic techniques for delineating
areas where economic responses can be expected from fertilizer
additions.
The two major diagnostic techniques used in forestry are foliar
and soil analyses. In the limited number of studies conducted to
date, foliar analysis has proved more effective than soil analysis
for predicting the response of southern pines to P fertilization
(13, 20, 21). However, since most fertilizer applications to young
stands are made at time of planting, foliar analysis cannot be
used because of the absence of growing trees on the site.
Soil total P has been used with some success for predicting P
fertilizer requirements of slash pine (Pinus elliotti var. elliottii
Engelm. ) in Australia (6), but it has been less useful elsewhere
(13). In the Coastal Plain region of the southeastern United
States, P extracted by NH4OAc buffered at pH 4.8 (13) or by 0.05N
HCl+0.025N HSO, (21) has proved more successful than
total P, or P extracted by other procedures, for predicting re-
sponse of southern pines to P fertilization. However, in a recent
evaluation of the effectiveness of a variety of soil testing proce-
dures it was reported that P extracted by NHOAc (pH 4.8)
provided a good index of response of slash pine in the first year
following fertilization but not over growth periods exceeding 1
year (3). Conversely, P extracted by 0.05N HC1+ 0.025N H2SO,
provided a good index of response for growth periods of 3 to 5
years following P fertilization, but not for the first year follow-
ing fertilization. In these evaluations (3), a limited number of
Coastal Plain soils were used and no attempt was made to relate
particular soil test values against P fertilizers required to achieve
optimum growth of slash pine.
Results are reported in this bulletin of a study designed to (a)
select a soil test suitable for use over the range of soils en-
countered in the Coastal Plain, and (b) calibrate it against the






amount of P fertilizer required to achieve optimum growth of
slash pine during the initial years of the rotation period.

Materials and Methods
Field trials
All soil and foliage samples and tree growth information were
obtained from a series of uniform factorial fertilizer experiments
established at time of planting slash pine in 1968. Fertilizer N
and P were each applied at rates equivalent to 0, 20, and 80 lb/
acre, (0, 22.5, and 90 kg/ha) in all combinations. The materials
were surface applied in 4-foot (1.2-m) bands down bedded rows
10 feet (3 m) apart, resulting in concentrations of nutrients in
the bands of 2.5 times that applied. The treatments were ran-
domly applied in three blocks at 29 locations throughout the lower
Coastal Plain, giving a total of 72 blocks or sites. Test locations
were selected to represent the principal forest soils of the region.
Details of experimental design, soil properties, and responses
found 3 years after fertilizer application of this series of trials
were reported by Pritchett and Smith (15).

Soil samples
Four composite soil samples were collected in December, 1971
(4 years after establishment of the trials), from the 72 control
plots of the 24 trials (5 trials were discarded because of fire
damage, poor survival, etc.). Two samplings were collected from
the 0-8 inch (0-20 cm) depth-one from the bedded area and the
other from the undisturbed interbed area-and one each from
the 8-16 and 16-24 inch (20-40 and 40-60 cm) depths. Each soil
sampled consisted of a minimum of 12 cores, collected with a 1.5
inch (4 cm) closed cylinder soil tube. Depth of the A, horizon
and depth to a root-limiting horizon (mottled, spodic, or argillic),
occurring within the surface 36 inches (91 cm), were also re-
corded. These experimental sites were classified within one of
five drainage classes by CRIFF1 personnel at time of establish-
ment (15). Soil samples were air-dried and passed through a
2-mm sieve prior to analysis.

Foliage samples
Foliage samples were collected in December 1971 from trees
1 CRIFF is an acronym for Cooperative Research in Forest Fertilization, a
research program jointly sponsored by the University of Florida and
Industry.






in the control plot of each of the three replicates at each site.
Each sample consisted of a composite of needles collected from a
minimum of five trees per plot. The trees were selected to repre-
sent the range in tree size and vigor found in the plot. Needles
were taken from the previous 'spring' flush on the uppermost
whorl bearing secondary branches. All samples were dried at 70 C
and ground to pass a 1-mm sieve prior to chemical analysis.

Tree growth and response parameters
Heights of all living trees were determined by CRIFF coopera-
tors at the end of the first, third, and fifth growing seasons. Re-
sponses recorded after three growing seasons were reported by
Pritchett and Smith (15).
The index of tree growth in the absence of P fertilizers was
taken as the tallest mean height for the three treatments which
had received no P application but had received one of three N
application rates (0, 22.5, or 90 kg N/ha). These values were ob-
tained for growth periods of 1, 3, and 5 years for each replicate
at all sites.
Relative tree height was used as the index of response to P
fertilizer. This was calculated as follows:
Height in the absence of P fertilizer
Relative height= X 100 (a)
Maximum height from P addition
Maximum height from P addition, adjusted for N responses, was
predicted by first fitting response curves to the height data by
using a second degree polynomial equation.
Y=a+ bX+cX2 (b)
where Y= tallest mean height in any N treatment, X= P applica-
tion rate (0, 22.5, and 90 kg P/ha), and a, b, and c are constants.
The predicted maximum height was then calculated by differenti-
ating the equation, setting the derivative equal to zero solving
for X, and then determining the value of Y in the original equa-
tion corresponding to the value found for X. By substituting the
maximum heights derived from the polynomial equation (b) into
the formula (a), relative heights were computed for each repli-
cate at all sites for growth periods of 1, 3, and 5 years. In some
cases, it was not possible to obtain a predicted maximum in this
manner, because the response was either linear or it increased
exponentially with increasing rates of P. In these cases the maxi-
mum height was taken as the actual mean height in the treatment






producing the tallest trees. Where no increase in height occurred
following P application, relative height was recorded at 100%.
The amount of P fertilizer required to achieve maximum height
was obtained by differentiating the quadratic equation, setting
the derivative equal to zero and solving for X; i.e. where X=
-b/2c. The amounts of fertilizer required to achieve 90% and
95% of maximum height were also computed. These values were
obtained by substituted 90% and 95% of maximum tree height
values in the quadratic equation and solving for X. In cases
where actual rather than predicted maximum height was used,
the P fertilizer required for maximum height was taken as the
actual P rate of the treatment that produced the maximum
height.

Sample analysis
Phosphorus was extracted from soil samples by the five test
methods shown in Table 1. Inorganic P in the extracts was deter-
mined by the ascorbic acid reductant technique (19).
Particle size distribution was calculated by the hydrometer
method (7), pH was measured in a 1:2 soil-water mixture, and
moisture contents were determined with a pressure membrane
apparatus at 15 and 1/3 atmosphere (17). Soil organic matter
was determined by a modified Walkley-Black method (1), total
N by the macro-Kjeldahl procedure (8), and cation exchange
capacity (CEC) by NH4 saturation with N NHO4Ac at pH 7.0
(10). Calcium, Mg, and Al in NH4OAc (pH 4.8) extracts were
determined by atomic absorption, and K by flame emission spec-
troscopy.
Foliage samples were ashed at 480 C for 5 hours. The ash was
dissolved in 6N HC1, digested on a hot plate for 15 minutes and

Table 1. Solutions, soil:solution ratios, and shaking time used in extracting
P from soil samples.
Soil: Shaking
Method* Extractant solution time Ref.
ratio min.
H20 H20 1:5 30 -
NH40Ac 0.7N NH40Ac+0.54N HOAc (pH 4.8) 1:5 30 (11)
HCI-H2S04 0.05N HCI+0.025N H2SO4 1:4 5 (11)
NH4F-HCI-1 0.03N NH4F+0.025N HCI 1:5 30 (11)
NHiF-HCI-2 0.03NNH4F+0.1NHCI 1:10 1 (11)
SIn the text and tables the methods are referred to by these abbreviations.
4







P in the solutions was determined by the procedures used with
soil extracts.

Relationships between soil test values and tree growth and response
Relationships between soil test values and tree height growth
and response to treatments were computed using a logarithmic
transformation of the soil test value to account for the curvi-
linear nature of the relationships (3). The square of the multiple
correlation coefficient (R2) for this model was taken as the index
of the effectiveness of the soil test methods for predicting tree
parameters.

Results and Discussion
Relationships between soil test values and relative heights

The effectiveness of the five soil test methods for predicting
relative heights, on the basis of P extracted from the surface 8
inches (20 cm) of soil (Table 2), were similar to those reported
earlier by Ballard and Pritcaett (3). The amounts of P extracted
by HO were more closely related to response (relative height)
after 1 year of growth than P extracted by other methods; while


Table 2. Relationships between P extracted from the surface soil and within
the effective soil depth (volume), and relative height of slash pine
1, 3, and 5 years after P fertilization.
Soil test Soil Relative height
method sample 1 year 5 years 3 years
.... .. .. ...........
H20 0-20B cmt 0.322* 0.149"* 0.120**
0-20 cm 0.306" 0.132"* 0.100**
Volume 0.372 0.239 0.191*"
NH40Ac 0-20B cm 0.281** 0.157* 0.084*
0-20 cm 0.270* 0.137 0.072"
Volume 0.253"* 0.220'* 0.142**
HCI-H2S04 0-20B cm 0.306** 0.246** 0.143"*
0-20 cm 0.264** 0.224" 0.126**
Volume 0.274" 0.322 0.211*
NH4F-HCI-1 0-20B cm 0.259"* 0.221"* 0.113*
0-20 cm 0.235"* 0.198* 0.095"*
Volume 0.282* 0.284" 0.162**
NH4F-HCI-2 0-20B cm 0.188** 0.210** 0.123**
0-20 cm 0.152* 0.178"" 0.094**
Volume 0.211* 0.303* 0.202**
t 0-20B represents soil samples collected from the bedded area.
% Significant at the 5% level, using the model Y=b logX+c.
SSignificant at the 1% level, using the above model.







P extracted by HCI-HISO4 and the two NH4F-HCI methods
tended to be more closely related to response after 3 and 5 years
of growth. The HC1-H2SO, method was the most effective test
overall. A better prediction was achieved using soil samples col-
lected from the bedded area, as opposed to the interbed area.
This was anticipated because nearly all rooting activity of young
trees is within the bedded area (11).
The relationships between P extracted by HCl-HSO, from the
0-8 inch (0-20 cm) depth from beds and relative height of slash
pine 1, 3, and 5 years after P fertilization are shown in Figure 1.
Applying the Gate and Nelson (9) technique of determining the
critical level of soil P, it was found that a soil test value of 5 ppm
P provided the best separation of responsive and non-responsive
sites, assuming that a relative height of 90%, or above, repre-
sented no significant response. The separation of the 72 field sites
into response quadrants, using soil test values above or below
5 ppm P and 90% relative height, is shown in Table 3.
The data in Table 3 illustrate three points. First, the use of
5 ppm P extractable by HC1-HSO, provides a reasonably good
separation between responsive and non-responsive sites. Second,
as the growth period increased, the number of sites with extract-
able P>5 ppm decreased. This is probably because some of the
sites had low H,0-extractable P, resulting in an early
growth response to applied P, which disappeared over longer
growth periods as the trees began to make use of the less soluble
HCl-H2SO-extractable P. Third, the number of non-responsive
sites with less than 5 ppm extractable P increased with an in-
crease in the growth period from 3 to 5 years. This may have
arisen because factors other than P became limiting to growth
of trees over the longer growth period, or else insufficient P was


Table 3. Separation of 72 field sites into response quadrants using the tech-
nique of Cate and Nelson (9) and a critical HCI-H2S04-extractable
P value of 5 ppm.
Tree HCI-H2S04<5 ppm P HCI-H2SO4>5 ppm P Correct*
age Response No response Response No response prediction

1 34 12 9 17 70.8
3 34 12 6 20 70.8
5 27 19 6 20 65.3

Correct prcti Response (<5 ppm P)+No response (>5 ppm P) X 100.
Correct predictTotal number of sites






$> -- -- r- -h-, -- -
100 *. *



0: *.*
i o I
S60 (I year after fertilization)


J 40 -



20 5 10 15 20 25 30 55
100 .* *


O- *
C *:.

Ld 60 yearsas after fertilization)


W40- *
c I


20 I I l I
0 5 10 15 20 25 30 55
100 09 ,
- "-' I "*---' "-^ --

80-- *
S ,** I
i I
, 60 -. (5 years after fertilization)



*
0 40 -


20 l I I I I I
0 5 10 15 20 25 30 55
HCL-H2S04 EXTRACTABLE P, PPM
Figure 1. Relationships between P extracted by HCI-H2S04 (X) and relative
height of slash pine 1, 3, and 5 years (Y1, Y3, Y5) after fertiliza-
tion.







applied initially to maintain an adequate P supply to the trees
over 5 years. Another possible factor which may have contributed
to the decline in effectiveness of the soil test over the 5-year
growth period is the contribution of soil P from profile depths
below 8 inches (20 cm). Data in Table 4 show that extractable P
within the effective rooting volume (computed as the sum of ex-
tractable P values in profile samples down to a limiting horizon),
provided a better index of prediction than extractable P in the
surface soil when comparing relative height at ages 3 and 5
years. This strongly suggested a significant contribution to the
available P supply from lower depths, where roots were capable
of penetrating free of impedance from restrictive horizons
(mottled, spodic, or argillic).
Several other soil and site parameters were significantly cor-
related with relative height (Table 4). However, many of the
parameters were significantly correlated with H20- and /or HC1-
HSO,-extractable P (Table 5). Thus, since relative height is an
actual recorded response to P fertilizer application in the field, it


Table 4. Relationships between selected soil and site properties and relative
height of slash pine 1, 3, and 5 years after P fertilization on 72 sites.


Soil or sitet Relative height
property 1 year 3 years 5 years
......... ... R ............
pH 0.089* 0.083* 0.097*
Organic matter 0.013 0.038 0.008
Nitrogen 0.149** 0.216** 0.143**
CEC 0.020 0.030 0.035
NH40Ac (pH 4.8)-extractable:
Ca 0.217"* 0.175** 0.252
Mg 0.019 0.005 0.029
K 0.047 0.044 0.019
Al 0.257** 0.145** 0.144
Silt+clay 0.347"" 0.225** 0.149*
Available moisture 0.227** 0.095 0.017
Depth of A1 horizon 0.056 0.050 0.032
Depth to limiting horizon 0.281** 0.314"* 0.345**
Drainage class 0.189** 0.237 0.274"*
t Except for depth functions and drainage class, all properties are for the surface 20 cm
of soil.
SSignificant at the 5% level, using the model Y=aX+bX2+c.
Significant at the 1% level.








Table 5. Simple correlation coefficients (r) between selected soil and site properties of 72 field sites.

Soil or site Extractable P NH40Ac Silt + Depth to Drainage
property H20 HCI-H2S04 pH Ca Al clay LH class



pH -0.713"" 0.250" 1.000 -
Organic matter 0.168 -0.097 -0.394** 0.036 0.041 0.360** -0.277 -0.351 *
Nitrogen -0.047 -0.157 -0.293" -0.004 0.207 0.458** -0.289" -0.387*"
CEC 0.101 -0.124 -0.295" 0.263* 0.202 0.494"" -0.207 -0.313**
NH40Ac (pH 4.8)-
extractable:
Ca 0.249* -0.113 -0.033 1.000 -
Mg 0.469" -0.075 -0.337"" 0.727"* 0.092 0.344** -0.168 -0.185
K 0.077 -0.199 0.009 0.535"" 0.377"" 0.639"" 0.067 0.099
Al -0.623" -0.126 0.401** 0.019 1.000 -
Silt+clay -0.424** -0.253* 0.271* 0.274** 0.715** 1.000 -
Available moisture -0.329"" -0.180 0.169 0.215 0.587"* 0.907** -0.030 -0.055
Depth of Al horizon 0.141 0.232* -0.007 -0.216 -0.177 -0.252* 0.122 -0.063
Depth to LHt -0.070 0.292* 0.602"" 0.021 -0.161 -0.049 1.000 -
Drainage class -0.244 0.188 0.697"" 0.012 -0.017 0.077 0.852"" 1.000
S Significant at the 5% level.
Significant at the 1% level.
t Depth to limiting horizon.






is likely that most of the significant relationships shown in Table
4 exist, because such parameters as depth to a limiting horizon
are either related to available soil P levels or in some manner
influence the response of trees to added P fertilizer.
Although certain site or soil parameters provided as reliable
an index of response as extractable soil P, particularly over the
longer growth periods, extreme caution should be used in extra-
polating these results to other sites. Only where relationships are
known to be causal, such as between extractable soil P and re-
sponse to P fertilizers, can they be used with confidence for pre-
diction purposes on sites with soil properties within the range
encountered in the calibration study.

Relationships between soil test values and heights
of unfertilized trees
In order to convert predicted relative height response into an
absolute growth response, which is the criteria needed for eco-
nomic justification of fertilizer additions, a prediction of height
(height growth in the absence of P fertilizer) is required.
Relationships between soil test values and height (Table 6)
showed that only P extracted by HO provided a reasonable pre-
diction of height. Ballard and Pritchett (3) suggested that the

Table 6. Relationships between P extracted from the surface soil and within
the effective soil depth (volume), and height of unfertilized slash
pine after 1, 3, and 5 years of growth.
Soil test Soil Height
method sample 1 year 3 years 5 years
... ... R . .. .. .
H20 0-20B cmt 0.370"* 0.297 0.193*"
0-20 cm 0.369"" 0.324** 0.209 *
Volume 0.258** 0.329** 0.238*
NH40Ac 0-20B cm 0.189** 0.179** 0.086*
0-20 cm 0.193* 0.195"* 0.084*
Volume 0.071" 0.122** 0.062"
HCI-H2S04 0-20B cm 0.024 0.087* 0.072"
0-20 cm 0.012 0.082* 0.063*
Volume 0.000 0.059" 0.055
NH4F-HCI-1 0-20B cm 0.003 0.046 0.042
0-20 cm 0.002 0.049 0.040
Volume 0.006 0.056 0.041
NH4F-HCI-2 0-20B cm 0.015 0.007 0.014
0-20 cm 0.018 0.006 0.010
Volume 0.012 0.024 0.028
t 0-20B represent soil samples collected from the bedded area.
SSignificant at the 5% level, using the model Y=b logX+c.
** Significant at the 1% level.







failure of P extracted by stronger extractants, such as the HC1-
HS04 method and solutions containing fluorides, to provide a
reasonable estimate of height over longer growth periods was
due to some other growth-limiting factors than inadequate avail-
able soil P, such as insufficient soil moisture.
Several other soil and site parameters, including pH, NHOAc-
extractable Ca and Al, available moisture, depth to a limiting
horizon (LH), and drainage class were all significantly related
at the 1% level to tree height at 1 year of age (Table 7). How-
ever, all of these parameters, except depth to LH and drainage
class, were also significantly correlated with HO-extractable P
(Table 5), suggesting that they influenced growth mainly through
their effect on or association with H.O extractable P. The value
of both depth to LH and drainage class, as predictors of height,
increased with increasing growth period. These two parameters
were themselves also closely related (Table 5).
For prediction purposes, depth to LH probably has an advan-
tage over drainage class since its measurement involves a less
subjective assessment than drainage class. The relationship be-

Table 7. Relationships between selected soil and site properties and height
and height of slash pine after 1, 3, and 5 years of growth.
Soil or site Height
property 1 year 3 years 5 years
.. .. .. R ... .. .
pH 0.412"* 0.224** 0.142**
Organic matter 0.083" 0.074 0.096"
Nitrogen 0.029 0.074 0.017
CEC 0.056 0.089* 0.105*
NH40Ac (pH 4.8) extractable:
Ca 0.134** 0.151"* 0.117"
Mg 0.113" 0.086" 0.076
K 0.092" 0.067 0.101"
Al 0.307** 0.296"* 0.148**
Silt+clay 0.232** 0.240** 0.105*
Available moisture 0.213** 0.207** 0.059
Depth of Al horizon 0.008 0.094* 0.154**
Depth to limiting horizon 0.231** 0.323** 0.424**
Drainage class 0.306** 0.497** 0.456**
Significant at the 5% level, using the model Y=aX+bX2+c.
"" Significant at the 1% level.








500 **
E .. *
N .. *




S300 .


/
< 300 *



0 200
/
/
r Y 80.10 + 11.56X 0.09X2 (R2=0.424)


1 0 s1 30 45 60 75 90
DEPTH TO LIMITING HORIZON,cm
Figure 2. Relationship between depth to limiting horizon (X) and height of
slash pine after 5 years of growth.
tween depth to LH and height of slash pine after 5 years of
growth is shown in Figure 2. Although not shown, the relation-
ship between depth to LH (X, cm) and height of slash pine after
3 years of growth (Y, cm) was described by the quadratic equa-
tion.
Y=26.24+6.25X-0.05X2 (R2=0.323)
Barnes and Ralston (5), in an examination of soil factors affect-
ing growth of slash pine in Florida, also found depth to a fine-
textured horizon and depth to mottling to be significantly related
to site quality of slash pine. The form of the relationship reported
by these authors was the same as that shown in Figure 2. Height
increased with increasing depth to a LH up to a maximum, there-
after a further increase in depth was associated with a decline
in height. Barnes and Ralston (5) interpreted this relationship
in terms of the effect of soil moisture and aeration on growth.
The optimum depth of 20 to 30 inches (51 to 76 cm) to a fine-
textured horizon or mottling reported by these authors corres-
ponds closely to that shown in Figure 2. In view of the significant
correlation between depth to LH and P extracted by HCl-H2S0,
(Table 5), the success of depth to LH as a predictor of height
may be attributed to an integrated index of both the moisture
and P supply to the tree.






Relationships between foliar P, tree parameters, and soil test values
Foliar P was more closely related to relative height than soil P
extracted by any of the soil test methods (Figure 3). This is in
agreement with the findings of other workers (13, 21). Since
foliar P is a more direct measurement of the P available to trees,
which integrates all factors of soil P supply including soil depth
and time functions, these results should not be surprising. Foliar
P values corresponding to a relative height of 90% at ages 1, 3,
and 5 years in the range 0.085-0.095%, which corresponds closely
to the critical range proposed by Pritchett (13). Although it is
not the objective of this study to calibrate foliar P levels against
tree parameters, the critical values (range) obtained from the
close relationships shown in Figure 3 can be used to confirm
critical soil test values proposed from relationships between rela-
tive height and soil test values.
Multiple correlation coefficients for the relationships between
foliar P and soil test values showed that the amounts of soil P
removed by the stronger extractants (HC1-HSO0 and the two
NH4F-HC1 methods) were more closely related to foliar P than
amounts removed by the weaker extractants (HO and NH4OAc)
(Table 8). The importance of soil P at rooting depths below the
surface 8 inches (20 cm) was again illustrated by the larger


100


-r-





S /, oY(1)=137.0logX + 231.9 (R2=0.506)
-- 40 OY(3)=150.5logX + 246.2 (R20.5-44)
J 6,Y(5)=130.7logX 228.8 (R2=0.485)
I l


20 c 0.05 0.66 0.67 0.08 0.9 0"0 01
FOLIAR P, %/o


Figure 3. Relationships between P concentrations in foliage (X) of 4-year-
old slash pine and relative height of slash pine 1, 3, and 5 years
(Y1, Y2, Y5) after P fertilization.
13






Table 8. Relationships between P extracted from the surface soil and within
the effective soil depth (volume), and P concentrations in the foliage
of 4-year-old slash pine.
Soil test Soil sample
method 0-20B cmt 0-20 cm Volume


H20 0.159"* 0.183*" 0.357**
NH40Ac 0.273** 0.271** 0.479*"
HCI-H2S04 0.588** 0.644** 0.708""
NH4F-HCI-1 0.602"" 0.618*" 0.627**
NH4F-HCI-2 0.601** 0.617 0.675 *
t 0-20B represents soil samples collected from bedded areas.
"* Significant at the 1% level, using the model,
Y=b logX+c, where X=soil test value.

R2 values obtained by using P extracted from the effective root-
ing depth.
The relationship between foliar P and P extracted by
HC1-HSO is illustrated in Figure 4. The HCI-H2SO, value corres-
ponding to a foliar P concentration of 0.085% was 4.5 ppm, which
is in good agreement with the value of 5 ppm proposed above as
useful for separating responsive and non-responsive sites. From
the equation relating foliar P (Y) and NH4F-HCI-1 extractable
P (X),
Y=0.0189 logX4 0.0684
the NHF-IICl-1 P value corresponding to 0.085% P in the fol-
iage was calculated to be 7.5 ppm, while the corresponding value
for NHF-HCI-2 was calculated to be 9.8 ppm from the following
equation:
Y= 0.0231 logX +0.0620.

Relationships between soil test values and P fertilizer requirements
Multiple correlation coefficients for relationships between soil
test values and the amount of P fertilizer required to achieve
90, 95, and 100% of maximum height growth after 1, 3, and 5
years growth in the field are shown in Table 9.
The effect of increasing growth period on the effectiveness of
the five soil test methods as predictors of fertilizer requirements
was similar to that observed for relative height. The amounts
of P extracted by a weak extractant (NH4OAc) were most close-
ly related to P requirements of 1-year-old trees, while at ages 3
and 5 years, P extracted by the stronger extractants was most
closely related to fertilizer P requirements. While the HC1-H2SO0







method was the most effective predictor of relative height at ages
3 and 5 years, there was a tendency for the NHF-HC1 methods
to be the most effective predictors of fertilizer requirements for
trees of these ages.
For a given soil test method, the effectiveness of extractable P
in predicting the amounts of P fertilizer required to achieve 90%
of maximum height growth was not greatly different from their
effectiveness in predicting for 95% of maximum growth (Table
9). There was a pronounced decline in their effectiveness in pre-
dicting the amount of fertilizer required to achieve 100% of
maximum height growth, particularly at ages 1 and 3 years. This
was probably a function of the method of determining P require-
ments, rather than a true deterioration in the usefulness of soil
P for predicting P-fertilizer requirements. As mentioned in the
Materials and Methods section, where response curves could not
be fitted to data from any site, fertilizer requirements were taken
as the actual field application rate which provided the greatest
height growth. At several sites differences of less than 5% (rela-
tive height > 95%) were observed between the control and high-
est P treatment. These sites were recorded as requiring this
amount of P fertilizer to achieve 100% maximum growth. Many
of these small differences were probably non-significant and un-
related to soil P levels.
0.1C


009



cr


< '/
0.07. / "


0.06.' '. '
0.05 ^--- --- ----- ^ -----g -----^ ----^ ----^-->


2 4 6 b 10 12 14
HCI-H2S04 EXTRACTABLE P, ppm

Figure 4. Relationship between P extracted by HCI-HSO4 (X) and the con-
centration of P in the foliage (Y) of 4-year-old slash pine.








Table 9. Relationships between P extracted from the surface soil and within the effective soil depth (volume), and P fertilizer required
to achieve 90, 95, and 100% of maximum height growth after 1, 3, and 5 years of growth.


1 year


100 90


Fertilizer P requirements
3 years
95 100


................................................ R2 ...........
H20
0.271 0.250** 0.041 0.039 0.000 0.001
0.209"* 0.192** 0.035 0.035 0.000 0.000
0.237** 0.220** 0.034 0.084* 0.006 0.003


NH4OAc
0.359*" 0.364** 0.094** 0.116** 0.034
0.332** 0.334** 0.106** 0.098*" 0023
0.251** 0.239"* 0.071" 0.179"* 0.077*
HCI-H2S04
0.258"" 0.277" 0.085 0.189** 0.118"*
0.181** 0.199" 0.074" 0.173** 0.093**
0.158** 0.172** 0.043 0.256** 0.172""


0-20B cm 0.198*" 0.224** 0.076*
0-20 cm 0.164"* 0.180** 0.070*
Volume 0.199** 0.215** 0.066"


0-208 cm 0.147** 0.170""
0-20 cm 0.103"* 0.120"*
Volume 0.109** 0.120"*


0.048
0.051
0.030


NH4F-HCI-1
0.194"" 0.144**
0.170"* 0.120**
0.245** 0.179**
NH4F-HCI-2
0.192** 0.156"*
0.164** 0.126**
0.257** 0.204"**


0.014
0.012
0.034

0.071
0.070*
0.125"*

0.095**
0.091**
0.117**


0.005
0.005
0.042


0.014
0.013
0.056"

0.052
0.054"
0.128**


0.005
0.003
0.018

0.009
0.004
0.015

0.022
0.015
0.056*


0.056" 0.023
0.047 0.014
0.098"* 0.045


0.002
0.003
0.001

0.001
0.000
0.032

0.044
0.029
0.073"

0.065*
0.050
0.076"


0.111"* 0.070* 0.022 0.069"
0.111"* 0.058* 0.012 0.052
0.146** 0.149** 0.061" 0.092**


t 0-20B represents soil samples collected from bedded areas.
* Significant at the 5% level, using the model Y=b logX-t-c.
" Significant at the 1% level.


Soil
depth


0-20B cmt
0-20 cm
Volume

0-20B cm
0-20 cm
Volume

0-20B cm
0-20 cm
Volume


5 years







The relationships between P extracted by the HC1-H2S0O
method (0-20 cm samples from beds) and the amount of P fer-
tilizer required to achieve 90 and 95% of maximum height growth
are shown in Figure 5. The critical value of 5 ppm of extractable
P, proposed from the relationships with relative height, also pro-
vided a reasonable separation between sites requiring a prac-
tical P fertilizer application ( 20 lb P/acre or 22 kg P/ha)
and those which did not. The prediction curves for ages 1 and 3
years were somewhat similar, but the fertilizer requirements
over the 5-year period were considerably lower for any soil test
value below the 5 ppm. This may be a valid situation resulting
from a reduced requirement for high concentrations of P in the
surface soil as a consequence of roots exploiting larger volumes
of soil as the trees increase in age. At any rate, it appears that
the prediction models for 5 years are not definite for operational
fertilizer requirements. Drainage class was the only parameter
which provided a better prediction than extractable soil P, for
the amount of P fertilizer required to achieve 95% of maximum
height over any growth period (Table 10). Most other para-

Table 10. Relationships between selected soil and site properties and P
fertilizer required to achieve 95% of maximum height after 1, 3,
and 5 years of growth.
Soil or site Relationships for different growth periods
property 1 year 3 years 5 years
............ R' ........
pH 0.073 0.126** 0.046
Organic matter 0.003 0.199** 0.066
Nitrogen 0.083" 0.140"* 0.069
CEC 0.011 0.144" 0.061
NH40Ac (pH 4.8) extractable
Ca 0.069 0.003 0.031
Mg 0.000 0.096" 0.007
K 0.179** 0.079 0.000
AI 0.116* 0.005 0.025
Silt+clay 0.268"* 0.087" 0.051
Available moisture 0.225"* 0.098* 0.064
Depth of A1 horizon 0.015 0.009 0.002
Depth of limiting horizon 0.135"* 0.036 0.062
Drainage class 0.038 0.067 0.109"
Significant at the 5% level, using the model Y=aX+bX2+c.
*" Significant at the level 1% level.








oY(1)=-27.27logX + 3455 ( -0.258)

aW3)=-1993 lo X + 2812 (R20189)


oY(1)=-33.27IogX + 47.33 (R20.277)
oY(3)=-21.541ogX + 41.10 (R2=0.188)
r -- h 3


Si \ \ -.Uiiog + 2/.3(OU 0.022)
SY(5)=- 9.24 ogX + 15.85 (R2=0.052)

Z 4 40
L Z0
20 20





SW
" W
N
IL-


LL

0 2 4 6 1 0 2 46 10
HCI-H2S04 EXTRACTABLE P, ppm HCI-H2SO4 EXTRACTABLE P, ppm

Figure 5. Relationships between P extracted by HCI-H2SO4 (X) and amount of fertilizer P required to achieve 90 or 95% of maxi-
mum height growth of slash pine over periods of 1. 3, and 5 years (Y1, Y3, Y5) following fertilization.






meters discussed above, which were significantly related to fer-
tilizer requirements, were also significantly related to the amount
of extractable P (Table 5).

Summary and Conclusions
Data from the calibration study indicated that, for the purpose
of delineating P-responsive sites and the P-fertilizer require-
ments for the first 3 to 5 years following slash pine establish-
ment, the HC1-H2SO, or either of the NH4F-HC1 methods
were superior to the acid NHOAc method currently used
in Florida. Of these three the HC1-HSO, method is probably the
most suitable for this region, because (a) its prediction value
was at least as good as either of the NH4F-HC1 methods and (b)
the method is currently used on a routine basis by several
Southern states (12), and thus its use in Florida would offer an
opportunity for improved standardization and calibration. The
HCI-H2SO4 method is suited for large-scale routine determina-
tions in soil testing laboratories since the analytical procedure
is rapid and presents no problem from ion interference in the
colorimetric determination of P, and the extract can also be used
for the routine analysis of available cations.
From the results presented above, the following interpretation
of HCI-H,SO, test results is suggested. Soils containing < 5 ppm
of HCl-H2SO-extractable P should generally respond to applica-
tions of 20-40 lb P/acre (22-44 kg/ha) applied in a band 4 feet
(1.2 m) wide down the tree rows at or near the time of planting.
Soils testing below 2.5 ppm P should receive applications of 40-80
lb P/acre (44-88 kg P/ha). If the fertilizer is broadcast over the
entire soil surface rather than banded in the tree row, field ex-
perience has indicated that application rates approximately 50%
greater than those shown above should be used. For soil testing
below 2.5 ppm which have a high P-retention capacity (e.g., soils
containing 160 ppm or more of active Al), an application rate of
about 80 lb P/acre (88 kg P/ha) should be used. However, evi-
dence has suggested that even this rate may be inadequate for
periods longer than 5-10 years after establishment on some of
the most highly P-retentive soils (17).
The above recommendations for the HC1-HSO, method should
be used only in conjunction with a knowledge of the limitations
imposed by both the conditions under which the calibration was
conducted and the shortcomings of the soil test method. These can
summarized as follows:
(a) The fertilizer recommendations are based on the use of





concentrated superphosphate. As discussed by Ballard and
Pritchett (2), this source may be inferior to less soluble sources
such as ground rock phosphates on sites of either excessively low
or very high P-retention capacities.
(b) The recommendations are valid only for slash pine planta-
tions over a 3- to 5-year period following planting on prepared
woodlands unfertilized, acid, sandy soils in the Coastal Plain. For
determining the fertilizer needs of older established stands, or the
need to refertilize stands 5 or more years after fertilization at es-
tablishment, foliar analysis should probably be used.
(c) The recommendations are based on soil-test values for the
surface 8 inches (20 cm) of soil collected from within the bed.
Four years after bedding, when the samples for this study were
collected, there was only a small difference between extractable
P in surface samples collected from the bed and the interbed
area. However, shortly after bedding, these differences may be
substantial due to enhanced mineralization rates. Thus, in order
to apply the above recommendations soil samples should be col-
lected prior to bedding, or from the undisturbed area after bed-
ding. For sites where deeper root-penetratable horizons have
substantially higher extractable P levels than the surface 20 cm,
use of the surface sample may underestimate the P status. Simi-
larly, where the effective rooting depth is relatively large, the
use of surface samples may underestimate the P status of the
site. For instance, the relationship between foliar P (Y) and
HCI-H,SO, extractable P (X) on the 20 sites where depth to LH
was greater than 30 inches (75 cm) was
Y=0.0029X-0.00007X2+ 0.0796 (R2=0.588),
from which the extractable P value corresponding to a foliar P
concentration of 0.085% was calculated to be 2 ppm, this was
considerably less than the value of 5 ppm calculated from the
relationship found for all sites.
(d) In this study, HCl-HSO-extractable P values were cali-
brated against P-response information obtained from sites on
which possible N deficiencies had been corrected by applications
of N fertilizer. Thus, it is possible that on sites where both N
and P are deficient a response to P fertilizer may not be obtained,
even though the soil test indicates a response should result, be-
cause the N deficiency has to be corrected first. This situation will
exist for concurrent deficiencies of P and other growth-limiting
factors.
(e) Data presented by Ballard and Pritchett (4) indicated







that where insoluble basic calcium phosphates occur in soils with
a pH>5, the HCI-H.SO, method will overestimate the P status
of the soil. Thus high HC1-H1SO,-extractable P values from
nearly neutral soils should be treated with caution.

Acknowledgments
The authors wish to acknowledge the cooperators of the CRIFF
program on whose land the field trials were established. The
senior author acknowledges financial assistance from the Na-
tional Research Advisory Council of New Zealand and the CRIFF
program.



Literature Cited

S1. Allison, L. E. 1965. Organic carbon. p. 1346-1366. In C. A. Black
(ed.) Methods of soil analysis. Amer. Soc. Agron. Madison, Wis.
2. Ballard, R., and W. L. Pritchett. 1974. Phosphorus retention in Coastal
Plain forest soils: 11. Significance to forest fertilization. Soil Sci.
Soc. Amer. Proc. 38:363-366.
3. Ballard, R., and W. L. Pritchett. 1975. Evaluation of soil testing
methods for predicting growth and response of Pinus elliottii to
phosphorus fertilization. Soil Sci. Soc. Amer. Proc. 39(1):132-136.
4. Ballard R., and W. L. Pritchett. 1975. Utilization of soil and fertilizer
P compounds by slash pine seedlings. Soil Sci. Soc. Amer. Proc.
39(3):537-540.
5. Barnes, R. L., and C. W. Ralston. 1955. Soil factors related to growth
and yield of slash pine plantations. Fla. Agr. Exp. Sta. Tech. Bull.
559. 23 p.
6. Bauer, G. N. 1959. A soil survey of a slash pine plantation, Barcoon-
gere, New South Wales. Aust. For. 23:78-87.
7. Bouyoucus, C. J. 1951. A recalibration of the hydrometer method for
making mechanical analysis of soils. Agron. J. 43:434-438.
8. Bremner, J. M. 1965. Total nitrogen, p. 1149-1178. In C. A. Black
(ed.) Methods of soil analysis. Amer. Soc. Agron. Madison, Wis.
9. Cate, R. B., and L. A. Nelson. 1965. A rapid method for correlation
of soil test analysis with plant response data. N. C. State Univ.
Agr. Exp. Sta. Int. Soil Testing Series Bull. 1. 24 p.
10. Chapman, H. D. 1965. Cation-exchange capacity. p.891-901. In C. A.
Black (ed.) Methods of soil analysis. Amer. Soc. Agron. Madison,
Wis.
11. Haines, L. W., and W. L. Pritchett. 1964. The effect of site prepara-
tion on the growth of slash pine. Soil abd Crop Sci. Soc. Fla.
Proc. 24:27-34.
12. Page, N. R., G. W. Thomas, H. F. Perkins, and R. D. Rouse. 1965.
Procedures used by state soil-testing laboratories in the southern
region of the United States. Southern Cooperative Series Bull.
102. 49 p.







that where insoluble basic calcium phosphates occur in soils with
a pH>5, the HCI-H.SO, method will overestimate the P status
of the soil. Thus high HC1-H1SO,-extractable P values from
nearly neutral soils should be treated with caution.

Acknowledgments
The authors wish to acknowledge the cooperators of the CRIFF
program on whose land the field trials were established. The
senior author acknowledges financial assistance from the Na-
tional Research Advisory Council of New Zealand and the CRIFF
program.



Literature Cited

S1. Allison, L. E. 1965. Organic carbon. p. 1346-1366. In C. A. Black
(ed.) Methods of soil analysis. Amer. Soc. Agron. Madison, Wis.
2. Ballard, R., and W. L. Pritchett. 1974. Phosphorus retention in Coastal
Plain forest soils: 11. Significance to forest fertilization. Soil Sci.
Soc. Amer. Proc. 38:363-366.
3. Ballard, R., and W. L. Pritchett. 1975. Evaluation of soil testing
methods for predicting growth and response of Pinus elliottii to
phosphorus fertilization. Soil Sci. Soc. Amer. Proc. 39(1):132-136.
4. Ballard R., and W. L. Pritchett. 1975. Utilization of soil and fertilizer
P compounds by slash pine seedlings. Soil Sci. Soc. Amer. Proc.
39(3):537-540.
5. Barnes, R. L., and C. W. Ralston. 1955. Soil factors related to growth
and yield of slash pine plantations. Fla. Agr. Exp. Sta. Tech. Bull.
559. 23 p.
6. Bauer, G. N. 1959. A soil survey of a slash pine plantation, Barcoon-
gere, New South Wales. Aust. For. 23:78-87.
7. Bouyoucus, C. J. 1951. A recalibration of the hydrometer method for
making mechanical analysis of soils. Agron. J. 43:434-438.
8. Bremner, J. M. 1965. Total nitrogen, p. 1149-1178. In C. A. Black
(ed.) Methods of soil analysis. Amer. Soc. Agron. Madison, Wis.
9. Cate, R. B., and L. A. Nelson. 1965. A rapid method for correlation
of soil test analysis with plant response data. N. C. State Univ.
Agr. Exp. Sta. Int. Soil Testing Series Bull. 1. 24 p.
10. Chapman, H. D. 1965. Cation-exchange capacity. p.891-901. In C. A.
Black (ed.) Methods of soil analysis. Amer. Soc. Agron. Madison,
Wis.
11. Haines, L. W., and W. L. Pritchett. 1964. The effect of site prepara-
tion on the growth of slash pine. Soil abd Crop Sci. Soc. Fla.
Proc. 24:27-34.
12. Page, N. R., G. W. Thomas, H. F. Perkins, and R. D. Rouse. 1965.
Procedures used by state soil-testing laboratories in the southern
region of the United States. Southern Cooperative Series Bull.
102. 49 p.







13. Pritchett, W. L. 1968. Progress in the development of techniques and
standards for soil and foliar diagnosis of phosphorus deficiency in
slash pine. p. 81-87. In Forest fertilization theory and practice.
Tennessee Valley Authority, Muscle Shoals, Ala.
14. Pritchett, W. L., and W. H. Smith. 1970. Fertilizing slash pine on the
sands of the Lower Coastal Plain. p. 19-41. In C. T. Youngberg
and C. B. Davey (ed.) Tree growth and forest soils. Oregon State
Univ. Press, Corvallis.
15. Pritchett, W. L., and W. H. Smith. 1972. Fertilizer response in young
pine plantations. Soil Sci. Soc. Amer. Proc. 36:660-663.
16. Pritchett, W. L., and J. L. Gray. 1974. Is forest fertilization feasible?
Forest Farmer. 33 (8): 6-14.
17. Pritchett, W. L., and W. H. Smith. 1974. Management of wet savanna
forest soils for pine production. Univ. Fla. Agr. Exp. Sta. Tech.
Bull. 762. 22 p.
18. Richards, S. J. 1965. Soil suction measurements with tensionmeters.
p. 153-163. In C. A. Black (ed.) Methods of soil analyses. Amer.
Soc. Agron. Madison, Wis.
19. Watanabe, F. S., and S. R. Olsen. 1965. Test of an ascorbic acid
method for determining phosphorus in water and NaHCO, extracts
from soil. Soil Sci. Soc. Amer. Proc. 29:667-678.
20. Wells, C. G., and D. M. Crutchfield. 1969. Foliar analysis for predict-
ing loblolly pine response to phosphorus fertilization on wet sites.
Southeast. For. Exp. Sta., USDA For. Serv. Res. Note SE-128. 4 p.
21. Wells, C. G., D. M. Crutchfield, N. M. Berenyi, and C. B. Davey. 1973.
Soil and foliar guidelines for phosphorus fertilization of loblolly
pine. Southeast. For. Exp. Sta., USDA For. Serv. Res. Paper
SE-110. 15 p.












































RIC

Seming Mknlind
1875 1975


N T




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