• TABLE OF CONTENTS
HIDE
 Front Cover
 Title Page
 Acknowledgement
 Personnel
 Table of Contents
 Introduction
 Amazon Jungle of Peru
 Cerrado of Brazil (joint NCSU/Cornell...
 Intercropping
 Soil characterization
 Soil fertility capability classification...
 Economic interpretation
 Extrapolation activities
 Communications of results






Title: Research program on soils of the tropics, annual report for ...
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Permanent Link: http://ufdc.ufl.edu/UF00053920/00001
 Material Information
Title: Research program on soils of the tropics, annual report for ...
Alternate Title: Agronomic-economic research on soils of the tropics
Research on soils of the tropics
Abbreviated Title: Res. program soils trop., annu. rep.
Physical Description: 1 v. : ill. ; 28 cm.
Language: English
Creator: North Carolina State University -- Soil Science Dept
Publisher: The Dept.
Place of Publication: Raleigh N.C
Publication Date: 1978
Frequency: annual
regular
 Subjects
Subject: Soils -- Tropics -- Periodicals   ( lcsh )
Soils -- Periodicals -- Latin America   ( lcsh )
Agriculture -- Tropics -- Periodicals   ( lcsh )
Agriculture -- Periodicals -- Latin America   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
 Notes
Statement of Responsibility: Soil Science Department, North Carolina State University.
Dates or Sequential Designation: 1976-1977.
Funding: Electronic resources created as part of a prototype UF Institutional Repository and Faculty Papers project by the University of Florida.
 Record Information
Bibliographic ID: UF00053920
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000463846
oclc - 05742689
notis - ACM7672
lccn - 81642504
issn - 0277-5573
 Related Items
Preceded by: Tropical soils research program, annual report
Succeeded by: Agronomic-economic research on soils of the tropics

Table of Contents
    Front Cover
        Front Cover
    Title Page
        Page i
    Acknowledgement
        Page ii
    Personnel
        Page iii
    Table of Contents
        Page iv
        Page v
    Introduction
        Page 1
        Page 2
        Highlights
            Page 3
            Page 4
            Page 5
            Page 6
        Collaborating institutions and individuals
            Page 7
            Page 8
            Page 9
            Page 10
    Amazon Jungle of Peru
        Page 11
        Crop weather
            Page 12
            Page 13
            Page 14
            Page 15
        Continuous cropping experiments
            Page 16
            Page 17
            Page 18
            Page 19
            Page 20
            Page 21
            Page 22
            Page 23
            Page 24
            Page 25
            Page 26
            Page 27
        Fallow with kudzu study
            Page 28
            Page 29
            Page 30
        Varieties and some agronomic factors of corn production
            Page 31
            Page 32
            Page 33
            Page 34
            Page 35
            Page 36
            Page 37
            Page 38
            Page 39
            Page 40
            Page 41
            Page 42
            Page 43
            Page 44
            Page 45
        Phosphorus and sulfur studies
            Page 46
            Page 47
            Page 48
            Page 49
        Micronutrient research
            Page 50
            Page 51
            Page 52
            Page 53
            Page 54
            Page 55
            Page 56
            Page 57
            Page 58
            Page 59
            Page 60
            Page 61
            Page 62
        Integrating cropping systems
            Page 63
            Page 64
            Page 65
            Page 66
    Cerrado of Brazil (joint NCSU/Cornell research)
        Page 67
        Crop weather
            Page 68
        Residual lime effects
            Page 68
            Residual effect of lime on the clayey dark red latosol
                Page 68
                Page 69
                Page 70
                Page 71
                Page 72
                Page 73
                Page 74
                Page 75
                Page 76
                Page 77
                Page 78
                Page 79
                Page 80
            Residual effects of lime rate and incorporation depths
                Page 81
                Page 82
                Page 83
                Page 84
                Page 85
                Page 86
                Page 87
                Page 88
                Page 89
                Page 90
                Page 91
                Page 92
                Page 93
                Page 94
                Page 95
                Page 96
                Page 97
        Movement of Ca and Mg
            Page 98
            Page 99
        Residual P effects
            Page 100
            Residual P effects
                Page 100
                Page 101
                Page 102
                Page 103
                Page 104
            Residual effects of P rate, placement and time of application
                Page 105
                Page 106
                Page 107
                Page 108
                Page 109
                Page 110
                Page 111
                Page 112
        Residual zinc effects
            Page 113
        K and Mg fertilization
            Page 113
            Page 114
        Nitrogen fertilization
            Page 115
        Tolerance to Al toxicity and low available P
            Page 115
            Page 116
            Page 117
            Page 118
            Page 119
            Page 120
            Page 121
            Page 122
            Page 123
            Page 124
            Page 125
            Page 126
            Page 127
            Page 128
            Page 129
            Page 130
            Page 131
            Page 132
            Page 133
            Page 134
            Page 135
            Page 136
            Page 137
        Effects of P, lime and Si on P sorption, ion exchange and rice growth
            Page 138
            Page 139
            Page 140
            Page 141
            Page 142
            Page 143
            Page 144
            Page 145
            Page 146
            Page 147
            Page 148
        Outreach study of properties of Cerrado soils
            Page 149
            Page 150
            Page 151
            Page 152
            Page 153
            Page 154
            Page 155
            Page 156
            Page 157
            Page 158
            Page 159
            Page 160
            Page 161
            Page 162
            Page 163
            Page 164
            Page 165
            Page 166
            Page 167
            Page 168
            Page 169
            Page 170
            Page 171
            Page 172
            Page 173
            Page 174
            Page 175
            Page 176
            Page 177
            Page 178
        Intercropping research in North Carolina
            Page 181
            Page 182
            Page 183
            Page 184
            Page 185
            Page 186
    Intercropping
        Page 179
        Page 180
        Influence of iron oxides on soil color
            Page 203
            Page 204
            Page 205
            Page 206
            Page 207
            Page 208
            Page 209
        Comparing intercrops with monoculture
            Page 187
            Page 188
            Page 189
            Page 190
            Page 191
            Page 192
            Page 193
            Page 194
            Page 195
            Page 196
            Page 197
            Page 198
            Page 199
            Page 200
        Characteristics of some well-drained oxisols and ultisols of the savannas and rainforests of Venezuela
            Page 210
            Page 211
            Page 212
            Page 213
            Page 214
            Page 215
            Page 216
            Page 217
            Page 218
            Page 219
            Page 220
            Page 221
            Page 222
            Page 223
            Page 224
            Page 225
            Page 226
    Soil characterization
        Page 201
        Page 202
    Soil fertility capability classification system
        Page 227
        Page 228
        Modification of "i" modifier
            Page 229
            Page 230
            Page 231
            Page 232
            Page 233
            Page 234
        System assessment in the U. S.
            Page 235
            Page 236
            Page 237
            Page 238
            Page 239
            Page 240
            Page 241
            Page 242
            Page 243
            Page 244
    Economic interpretation
        Page 245
        Page 246
        Economic interpretation
            Page 247
            Page 248
            Page 249
            Page 250
            Page 251
            Page 252
            Page 253
            Page 254
            Page 255
            Page 256
    Extrapolation activities
        Page 257
        Page 258
        Pucallpa
            Page 259
        Other extrapolation sites
            Page 260
    Communications of results
        Page 261
        Page 262
        Publications
            Page 263
        Mailing list
            Page 264
        Conferences and symposia
            Page 265
            Page 266
        Utilization at farmer level
            Page 267
Full Text



AGRONOMIC-ECONOMIC RESEARCH

ON SOILS OF THE TROPICS



Annual Report for 1976-1977


Soil Science Department
North Carolina State University
Raleigh, N.C.


Contract


under
AID ta-C-1236


with the
U.S. Agency for International Development













RESEARCH PROGRAM ON SOILS OF THE TROPICS


ANNUAL REPORT FOR 1976-1977










Soil Science Department
North Carolina State University
Raleigh, North Carolina 27650













supported by


Contract AID/ta-C-1236
with the
U. S. Agency for International Development


November, 1978









ACKNOWLEDGEMENTS

I wish to take this opportunity to give a special word of thanks to Mrs. Dawn Silsbee for her
most excellent typing of the text of this annual report. Thanks are also given to Ms. Bertha
Monar and to Mrs. Ann Matrone for their respective excellent preparation of the tables and fig-
ures. Appreciation is given to the authors for their presentations and to Mr. Hugo Villachica
and Mr. Jot Smyth, without whose help the editing of this report would have been most
difficult.






John J. Nicholaides III, Coordinator
Tropical Soils Research Program








PERSONNEL


Administration
Charles B. McCants, Department Head
Pedro A. Sanchez, Program Coordinator1
John J. Nicholaides III, Program Coordinator2
Bertha I. Monar, Administrative Secretary
Dawn M. Silsbee, Bilingual Secretary
Cathy L. Langley, Research Technician
Lynn F. Dickey, Research Technician
Mary Jo Stephenson, Research Technician


Amazon Jungle of Peru
Dale E. Bandy, Project Leader
J. Hugo Villachica, Research Assistant
Jose R. Benites, Research Assistant
W. Couto, Visiting Assistant Professor
George C. Naderman Jr., Assistant Professor
D. Keith Cassel, Associate Professor
Stanley W. Buol, Professor
Michael K. Wade, Research Assistant
Cesar E. Lopez, Research Assistant


Cerrado of Brazil
K. Dale Ritchey, Project Leader (Cornell)3
Jose G. Salinas, Research Assistant
T. Jot Smyth, Research Assistant
Alfredo S. Lopes, Research Assistant
George C. Naderman Jr., Assistant Professor
Eugene J. Kamprath, Professor
Fred R. Cox, Professor
W. Couto, Visiting Assistant Professor
Enrique Gonzalez-Erico, Research Assistant
Russell S. Yost, Research Assistant


Intercropping Studies
Robert E. McCollum, Project Leader
Clifton K. Hiebsch, Research Assistant
Alvaro Cordero V., Research Assistant
Michael K. Wade, Research Assistant
Cesar E. Lopez, Research Assistant


Soil Characterization and Classification
Stanley W. Buol, Project Leader
W. Couto, Visiting Assistant Professor
Jerry M. Bigham, Research Assistant
Richard Schargel, Research Assistant
Robert A. Pope, Research Assistant


Economic Interpretation
Robert B. Cate Jr., Project Leader
Arthur J. Coutu, Professor (Economics)


Extrapolation
W. Couto, Project Leader
Stanley W. Buol, Professor


1Through 1976.
21977 present.

3Cornell University staff member working on cooperative project.









TABLE OF CONTENTS


Page

1 INTRODUCTION
1.1 Highlights ....................................................... 3
1.2 Collaborating institutions and individuals ............................... 7
2 AMAZON JUNGLE OF PERU
2.1 Crop weather..................................................... 12
2.2 Continuous cropping experiments..................................... 16
2.3 Fallow with kudzu study............................................ 28
2.4 Varieties and some agronomic factors of corn production. ................... 31
2.5 Phosphorus and sulfur studies........................................ 46
2.6 M icronutrient research ............................................. 50
2.7 Integrating cropping systems.......................................... 63
3 CERRADO OF BRAZIL (JOINT NCSU/CORNELL RESEARCH)
3.1 Crop weather .................. .................................. 68
3.2 Residual lime effects
A. Residual effects of lime on the clayey dark red latosol ................... 68
B. Residual effects of lime rate and incorporation depths ................... 81
3.3 Movem ent of Ca and Mg ............................................ 98
3.4 Residual P effects
A.Residual effects of lime and P on the loamy red-yellow latosol ............. 100
B. Residual effects of P rate, placement and time of application .............. 105
3.5 Residual zinc effects ............................................... 113
3.6 K and M g fertilization .............................................. 113
3.7 Nitrogen fertilization............................................... 115
3.8 Tolerance to Al toxicity and low available P ............................. 115
3.9 Effects of P, lime and Si on P sorption, ion exchange and rice growth ......... 138
3.10 Outreach study of properties of Cerrado soils ............................ 149
4 INTERCROPPING
4.1 Intercropping research in North Carolina ............................... 181
4.2 Comparing intercrops with monoculture ................................ 187
5 SOIL CHARACTERIZATION
5.1 Influence of iron oxides on soil color .................................. 203
5.2 Characteristics of some well-drained Oxisols and Ultisols of the savannas
and rainforests of Venezuela ......................................... 210







TABLE OF CONTENTS (Continued)


Page

6 SOIL FERTILITY CAPABILITY CLASSIFICATION SYSTEM
6.1 Modification of "i" modifier.................. ...................... 229
6.2 System assessment in the U. S.................. ..................... 235
7 ECONOMIC INTERPRETATION
7.1 Economic interpretation ............................................ 247
8 EXTRAPOLATION ACTIVITIES
8.1 Pucallpa......................................................... 259
8.2 Other extrapolation sites................. ......................... 260
9 COMMUNICATION OF RESULTS
9.1 Publications...................................................... 263
9.2 Mailing list ................ .................................... 264
9.3 Conferences and symposia............................................ 265
9.4 Utilization at farmer level .......................................... 267













INTRODUCTION


From the time the small farmer prepares his soil for planting, he is as interested in and affec-
ted by the economic return on his investment as he is the agronomic yield he will realize.










This is the sixth annual report of the Soil
Science Department's Research Program on
Soils of the Tropics and covers the period from
1976 through early 1977. Hence, this report
departs from precedent in that it will be called
Annual Report for 1976-1977. The bulk of the
1977 data will be included in the forthcoming
report, Annual Report for 1977-1978.
This research program has been supported by
the U. S. Agency for International Develop-
ment under Contract AID/ta-C-1236 which
runs for a three-year period from July 1, 1975
through June 30, 1978.
The overall objectives of the program have
been focused into developing economically-
sound soil-crop management systems for
1) acid tropical savannas and 2) acid tropical
rainforests. The field research activities, to
achieve these objectives, continue to be based
in Brasilia, Brazil for the savannas and in Yuri-
maguas, Peru for the jungle areas.
The final objective of the contract is to
gather additional information needed for estab-
lishing a sound basis for extrapolating the re-
search results to other tropical areas of the
world with similar soil management situations.
The three supporting activities to achieve this
objective are as follows: 1) Soil characteriza-
tion studies are used with basic laboratory and
greenhouse studies to determine the soil prop-
erties of little-known tropical areas in order to
better comprehend certain basic concepts not
fully understood at present; 2) the soil fertility
capability classification system (FCC) is uti-
lized as a practical means for grouping soils


with similar fertility limitations and thus
bridges the gap between the subdisciplines of
soil survey and soil fertility; 3) the data are
economically interpreted to evaluate the pro-
fitability of the proposed soil-crop manage-
ment systems and also to provide physical co-
efficients for economic planning means such as
linear programming and sector analysis. The
format for this report follows that established
by the 1975 Annual Report in that the staff re-
sponsible for each research project are identi-
fied to give more direct credit to the individ-
uals involved.


HIGHLIGHTS
Amazon Jungle
A new fertilization strategy in the contin-
uous cropping experiment successfully reversed
the severe crop yield decline which had oc-
curred in 1975. The main causes of the decline
were fertility-related. When the lime, N, P and
K rates were increased along with inclusion of
Mg, B, Cu and Mo fertilizers, yields of rice,
corn, soybeans and peanuts increased mark-
edly. Inference drawn from these findings is
that abandoned or soon-to-be-abandoned
chacras can be recovered and farmed contin-
uously and economically.
For example, using a rice/corn/soybean rota-
tion and no fertilizer or lime, a farmer in the
Yurimaguas area would realize a new profit of
$128/ha/yr on a plot of land that he would
normally abandon after two croppings. Uti-
lizing the 1974-1975 fertilizer strategy of
1000-240-79-240 kg/ha/hr of lime-N-P-K, the









farmer could realize a net profit of $579/ha/yr
on the same parcel of land. Employing the
same rotation on the same land area with the
improved 1976-1977 fertilization strategy of
1000-350-211-333 kg/ha/yr of lime N-P-K, the
farmer could obtain a new profit of $1539/
ha/yr. This $1539/ha/yr net profit represents
a 1202% increase over no fertilizer or lime and
a 266% increase over the lower fertilizer rates
of 1974 and 1975.
Viewed another way, the $ profit/$ invested
in fertilizer and lime was $2.66 for the 1976-
1977 strategy and $1.72 for the 1974-1975
strategy.
Utilizing the 1976-1977 fertilization strat-
egy, soybean and peanut yields increased to 2.5
and 4.5 tons/ha, respectively, while rice and
corn yields approached 3.5 and 4.0 tons/ha,
respectively.
As was noted in the 1975 Annual Report,
although the response to lime is great, the
residual effect of Ca(OH)2 is rather short-lived.
For instance, 1 ton Ca(OH)2/ha had a residual
effect of only 10 months. Corn yield response
to Ca(OH)2 applied 10 months earlier was
linear with yields increasing from 0 to 5.2
tons/ha as lime increased from 0-4 tons/ha. The
suggested application rates of 3-4 tons/ha/3-4
years appear agronomically feasible. By reduc-
ing Al saturation in the soil from 48 to 24%,
rice yields were increased to 3.5 tons/ha.
Preliminary research found that Mg and sev-
eral micronutrients became limiting after a
newly-cleared field had been twice cropped. A


micronutrient shotgun spray of Cu, Fe, Mn and
Zn sulfates and B, Mo, lime increased corn
yields from 1.2 to 5.2 tons/ha. Soybean yields
were increased less dramatically by this spray.
Each of the micronutrients were then eval-
uated in several crops. In a newly cleared and
burned chacra, soybean yields were increased
from 1.5 to 2.1 tons/ha with the 2 kg Cu/ha
and from 2.1 to 2.6 tons/ha with 0.5 kg B/ha.
Soybean yields decreased to 2.1 tons/ha when
B rates exceeded 0.5 kg/ha. Soybeans did not
respond to Mo, Mn or Zn. Also on newly
cleared and burned land, peanut yields were in-
creased from 3.0 to 4.5 tons/ha with applica-
tion of 0.5 kg B/ha and from 3.8 to 4.5 tons/ha
with 1.5 g Mo/kg seed.
When chacras are continuously cropped, one
would expect response to B, Mo and Cu appli-
cations. No soybean or peanut response to Zn
or Mn was obtained. However, the question re-
mains as to how this response or lack of re-
sponse to micronutrients will change as plants
utilize the native micronutrients in the soil.
Present data indicate the need to apply 0.5 and
1.0 kg/ha of B and Cu, respectively per crop of
soybeans and peanuts and 1.5 g Mo/kg peanut
seed.
An additional research emphasis was begun
to look at integrated cropping systems using
lower inputs and relay cropping. Preliminary
results have indicated no substantial negative
effect of the lower fertilizer and lime rates on
yields of relay-cropped rice, cowpeas, soy-
beans, peanuts, cassava and sugarcane.










A six-year kudzu fallow study was initiated
to determine whether it is possible to shorten
the traditional 20-year fallow period of the
slash-and-burn system for recycling of nutrients
to regenerate an exhausted soil. Should it be
possible to reduce the fallow period to 4 years,
a small farmer could permanently farm 5 hect-
ares by rotating a 1-ha cropping area/yr with
4 hectares in different stages of fallow.
The evaluation of adaptation of corn vari-
eties to the Yurimaguas environment found
that the relatively short, lodging resistant and
early maturing Amarillo Planta Baja outyielded
all other varieties tested under both adequate
and low lime and fertilizer levels. Corn grain
yields of this variety at the two fertility condi-
tions were 3.86 and 2.09 tons/ha, respectively.
Yields of all 10 varieties planted in September
exceeded those planted in April by 43%, due
primarily to improved rainfall distribution
during the latter growing season.
The establishment of a meteorological sta-
tion at the Yurimaguas Experiment Station has
allowed for the first detailed views of the cli-
matic pattern of the area. These detailed data
will allow for improved interpretation of the
agronomic research results.
Sava n nas
The long-term experiments on the residual
effects of liming and fertilizer applications on
Oxisols of the Cerrado of Brazil continued for
the fourth year. The original application of
8 tons lime/ha incorporated deep (0-30 cm)
continued to provide the maximum corn yield
although shallow incorporation was only


slightly inferior. Chemical soil analysis and
depth of rooting measurements indicated that
downward movement of Ca and Mg in the deep
and shallow lime incorporation treatments has
diminished the differences in subsoil acidity
between incorporation methods and the in-
creased rooting depth has improved water re-
serves for plants during dry spells. A corn expe-
riment with roots extending to a 120 cm depth
yielded 6 tons of grain/ha despite a 40-day dry
spell of which 19 days occurred after 50%
tasseling.
After six consecutive corn crops, two strate-
gies for obtaining desirable soil P levels were
evidenced. An initial broadcast application of
141 kg P/ha with maintenance applications of
35 kg P/ha before each crop provided yields
which were 80% of the treatment receiving an
initial broadcast application of 560 kg P/ha. A
cumulative yield of 72% of the maximum was
obtained with an application of 35 kg P/ha
broadcast and 35 kg P/ha banded before each
crop. Yearly differences in input/output cost
may dictate a given strategy. Based on October,
1976 prices it was economically feasible to
apply as much as 440 kg P/ha.
The satellite experiment on the loamy Red
Yellow Latosol continued to stress the impor-
tance of fully understanding the factors limit-
ing the utilization of Cerrado Oxisols. The high
available water content, lower P fixation and
decreasing Al saturation with depth in this soil
resulted in sustained high yields with lower
inputs of lime and P fertilizer.










A new experiment was installed to evaluate
response to K and Mg. Of special interest is the
application of 62 kg K/ha which almost
doubled corn grain yields providing a return
equivalent to 9.3 times the cost of the K fer-
tilizer.
For the fourth consecutive year corn grain
production was near 4 tons/ha in the absence
of applied N. Maximum yields were obtained
with the application of 200 kg N/ha, but 82%
of the maximum was produced with 80 kg
N/ha.
Studies on varietal tolerance to Al toxicity
and low available P were continued in both
greenhouse and field experiments. Among the
species and varieties studied the most tolerant
cultivars to P and Al stress were Taylor Evans
Y-101, Pratao Precoce, Agroceres-259 and
Carioca-1030 for sorghum, rice, corn and
beans, respectively. These studies indicate that
the most satisfactory method of crop manage-
ment on savanna Oxisols involves this use of
varieties tolerant to high Al saturation and low
available P combined with low levels of surface
applied lime.
Additional information on the properties of
Cerrado soils were obtained by on-campus
studies. Investigations on P sorption indicated
that previous P applications were more effec-
tive than liming materials in reducing addi-
tional P sorption, but the liming effects were
sufficient to cause overestimations in soil P re-
quirements for field conditions when P sorp-
tion measurements were performed on unlimed
soils. The increases in net negative soil charge
through the combined effects of P and lime


applications should have significant effects on
the ion retention properties of these Oxisols.
Large texture variations were observed
among 44 representative surface samples of
Cerrado soils. The chemical composition, ion
exchange and P sorption characteristics of
these samples varied according to surface tex-
ture. Water release characteristics resembled
those of sand irrespective of soil texture.
Intercropping
Field experiments in North Carolina have
compared the N response and productivity of
several intercropping combinations relative to
monocultures of the same crops. Land equiv-
alency ratios indicated that productivity was
increased when corn competed interspecifically
with soybeans or snapbeans. The proper selec-
tion of intercropping combinations was exem-
plified by the apparent nutritional incompati-
bility between intercropped corn and sweet
potatoes.
Considerations on some of the methods cur-
rently used in intercropping studies have re-
vealed that time is an important factor in com-
parisons of crops in mixture and monoculture.
The area-time equivalency ratio (ATER) is pro-
posed as a feasible method of accounting for
time in such comparisons.
Extrapolation
The mineralogy of iron compounds in chem-
ically similar pairs of red and yellow colored
soils indicated hematite and goethite were the
major iron components in the clay sized frac-
tions. Redness of the soils was associated with
increasing amounts of hematite relative to
goethite.










The "i" modifier in the FCC system, which
characterizes soils fixing considerable P by iron
compounds was evaluated over a broad range
of Oxisols, Ultisols and Alfisols. Results sug-
gested that a useful criterion is both a ratio of
iron oxides to percent clay greater than 0.15
and more than 35% clay in the plow layer.
Assessment of the FCC system was per-
formed using soybean experiments from 184
sites in southeastern United States. High yields
were obtained on a variety of soil conditions
using the appropriate management. Although
the required management depended largely on
soil properties the influence of these properties
on yield varied between years.
Characterization studies were continued in
the savanna and rainforest regions of Vene-
zuela. Soils from southern Venezuela were
more intensively weathered and had lower
effective CECs than soils of the northern
region. The Ultisols and Alfisols were con-
sidered intergrades to Oxisols when this cri-
terion was applicable.
Initial economic analysis of data produced
by the Yurimaguas program has focused on de-
fining factors necessary to produce near max-
imum yields. Various alternatives for producing
the different crops have been quantified.
Results from this phase of the analysis have de-
lineated specific areas where additional agro-
nomic research is necessary.


COLLABORATING INSTITUTIONS AND
INDIVIDUALS
The research reported is conducted in coop-
eration with several national and international


institutions and involves a high degree of
collaboration.
In the Amazon Jungle of Peru, field research
is conducted at the Yurimaguas Experiment
Station which is part of the Centro Regional de
Investigaciones Agropecuarias III ( CRIA III)
of the Ministerio de Alimentaci6n. Supporting
laboratory work is conducted at the La Molina
Experiment Station. The Direcci6n General de
Investigaciones of the Ministerio de Alimenta-
ci6n has assigned Dr. Carlos Valverde as project
leader, representing Peru. Dr. Valverde has
been very effective in expediting administrative
matters with the Peruvian Government. The
International Potato Center (CIP) plays a major
role in providing administrative and logistical
support. In turn, the program grows its potato
trials at Yurimaguas as the lowland tropical
station for adapting potatoes to the region. The
Peruvian meteorological network, SENAMHI,
established a meteological station at Yurima-
guas in 1976, which has allowed for the first
detailed looks at the climatic pattern of this
area.
In the Cerrado of Brazil, this project is con-
ducted jointly with Cornell University and the
Empresa Brasileira de Pesquisa Agropecuaria
(EMBRAPA) at the Centro de Pesquisa Agro-
pecuaria dos Cerrados, located about 40 km
north of Brasilia. The USAID Mission in
Brasilia and the Interamerican Institute of Agri-
cultural Sciences provided valuable logistical
support. EMBRAPA has assigned Mr. Edson
Lobato as project leader, representing Brazil.
Cornell and N. C. State staff stationed at the
Cerrado Center form an integral part of the
Center's research staff.










Several extrapolation studies are also col-
laborative in nature. Soil characterization stud-
ies have been conducted with partial financial
support in the form of scholarships for grad-
uate students from the USAID Mission to
Colombia, the Ministerio de Obras Publicas of
Venezuela, The Fundo de Amparo a Pesquisa
do Estado de Sao Paulo, Brazil. Data for eval-
uating the Fertility-Capability Soil Classifica-
tion System has been provided by EMBRAPA,
the Instituto Colombiano Agropecuario, Insti-
tuto Geografico Agustin Codazzi in Colombia.
The extrapolation work at Pucallpa, Peru is in
cooperation with the Instituto Veterinario de
Investigaciones Tropicales y de Altura (IV ITA).
Dr. Jos6 Toledo, as the individual in charge of
the Tropical Pasture Production and Evaluation
Research Line, is directing all extrapolation-
related activities at Pucallpa.
The following individuals from the dif-
ferent cooperating institutions provided sub-
stantial administrative support or are coauthors
of some of the research projects. We wish to
acknowledge and recognize their assistance at
this time.
PERU
Mariano Segura B., Director General de Investi-
gaciones Agrarias, Lima.
Carlos Valverde S., Project Coordinator for the
Ministry of Food and Director of the
Centro Regional de Investigaciones I-La
Molina.
Manuel Llaveria, Director del Centro Regional
de Investigaciones Agrarias IIl-Tarapoto.


Jos6 del Carmen Muro, Director de Investiga-
ciones, Ministerio de Agricultura, DGIA,
Lima.
Ruben Mesia P., Head, Yurimaguas Experiment
Station.
Mario Cano, Soils Department, La Molina
Experiment Station.
Humberto Mendoza, Plant Breeder, Interna-
tional Potato Center.
Richard L. Sawyer, Director General, Interna-
tional Potato Center.
Carlos Bohl P., Executive Director, Interna-
tional Potato Center.
William Hamann, Assistant Executive Director,
International Potato Center.
Oscar Gil, Controller, International Potato
Center.
Veronica de Franciosi, Assistant to Executive
Officer, International Potato Center.
Leonard Yaeger, Director, USAID/Peru
Ricardo Villalobos, Deputy Director, USAID/
Peru
John O'Donnell, Agricultural Officer, USAID/
Peru.
Milton Lau, former Food and Agriculture
Officer, USA ID/Peru.
Rollo Ehrich, former Deputy Food and Agri-
culture Officer, USAID/Peru.
BRAZIL
Jos6 Ireneu Cabral, President of EMBRAPA
Almiro Blumenschein, Director of EMBRAPA
Elemar Wagner, Director, CPAC, EMIBRAPA
Wenceslau G. Goedert, Associate Director,
CPAC, EMBRAPA.










Edson Lobato, EMBRAPA Project Coordinator
Gilberto Paez, Head of the Data Processing
Department, EMBRAPA.
Wilson V. Soares, former Associate Director,
Cerrado Center.
Jose M. Barcellos, former Head of the Brasilia
Experiment Station.
Frank Campbell, Chief, USAID Affairs Office-
Brazil.
William Rodgers, former Agriculture and Rural
Development Officer, USAID/Brazil.
William Gelabert, former Acting Director,
USAID/Brazil.
John Young, USAID/Brazil.
Matthew Drosdoff, Professor of Tropical Soils,
Cornell University.
David R. Bouldin, Professor of Soil Science,
Cornell University.


Robert B. Musgrave, Professor of Agronomy,
Cornell University.
Elcios Martins, Research Technician, Cornell-
NCSU Project.
Clibas Vieira, Professor, Universidade de
Vicosa.
Robert Schaffert, Brazilian National Sorghum
Program.
Ady Raul da Silva, Brazilian National Wheat
Program-CPAC.
Knut Mikaelson, Centro de Energia Nuclear na
Agriculture.
COLOMBIA
Servio T. Benavides, Instituto Geografico
Agustin Codazzi, Bogota.
Luis Alfredo Leon, Instituto Colombiano Agro-
pecuario, Palmira.
James M. Spain, Soil Scientist, CIAT, Palmira.










11







AMAZON JUNGLE OF PERU


-,
e ~*-,- a 1


-


Aerial view of Yurimaguas Agricultural Experiment Station.










Research at the Yurimaguas Experiment Sta-
tion in the Amazon Jungle of Peru in 1976-1977
continued to gather information for developing
agronomically and economically sound soil man-
agement practices for continuous cultivation in
jungle areas where population pressures dictate
an alternative to shifting cultivation. The expe-
rimental strategy followed continued to be that
of 1) determining the factors responsible for the
marked decline in crop yields following clearing,
typical of shifting cultivation in acid soils, and
2) the development of corrective measures to en-
able continuous cultivation in small farming
units with emphasis on low energy technology
options.
The research has dictated higher fertilization
levels in the central experiment of continuous
cropping, which now also includes micronu-
trients. The phosphorus and potassium studies,
as designed in earlier experiments, have contin-
ued. New experiments in 1976 and 1977 at the
Yurimaguas Experiment Station included
1) corn varietal response to various agronomic
practices, 2) lime, K, Mg and micronutrient
studies with rice, corn, peanuts and soybeans,
3) substituting kudzu fallow for forest regenera-
tion, and 4) integrating cropping systems. With
the new meteorological station established at the
Yurimaguas Experiment Station, the detailed cli-
matic pattern for this area was observed for the
first time.
As in the previous years, all experiments were
conducted on the Yurimaguas soil series Ultisol,
classified as Typic Paleudult, fine loamy, sili-
ceous, isohyperthermic, which is considered to
be representative of the region. Soil analyses re-
ported in the previous annual reports show the


soil to be deep, well drained, quite acid, low in
organic matter, and deficient in N, P, K, Ca, Mg
and, in some cases, S, B, and Mo. As earlier re-
ported also, the sandy topsoil texture contri-
butes to the susceptibility of this Ultisol to soil
compaction and at the same time, prevents any
serious phosphorus fixation problems.


2.1 CROP WEATHER
D. E. Bandy
In 1976 a meteorological station was estab-
lished at the Yurimaguas Experiment Station in
cooperation with SENAMHI, the Peruvian mete-
orological network, which has its area head-
quarters in Tarapoto. Most of the results presen-
ted in this report were taken at the Experiment
Station. Other results were provided by the
Yurimaguas Airport, which is 6 km from the
station.
For the first time, the detailed climatic pat-
tern for the Experiment Station can be observed
(Table 2.1:1). The greatest surprise is perhaps
that it is not as hot as one might expect, al-
though this does not mean that one does not
feel uncomfortable living there due to the high
relative humidity and low amounts of wind.
In terms of plant growth, the temperatures
are not too high during the day (absolute max.
35.80C or 960F) or night (avg. 22.50C or 710F)
to adversely affect plant growth or yield. On the
contrary, the temperatures are quite favorable
for such crops as maize, sugar cane, rice, cassava,
peanuts, and soybeans. A max-min temperature
reading system does not show the duration of
any temperature reading; thus, it is possible that
night temperatures are too high for most of the
night, falling very rapidly just prior to daybreak.








Table 2.1:1. Climatic data for the experimental station at Yurimaquas, Peru,


TEMPERATURE, C
RELATIVE SOLAR
MONTH Maximum Minimum Average PRECIPITATION WIND HUMIDITY RADIATION


30.8
31.5
31.0
30.5
30.6
30.6
30.1
31.2
32.6
32.1
31.7
31.1

31.2

35.8


22.0
22.2
22.3
21.9
22.5
21.9
17.9
19.9
19.6
21.1
21.1
21.2

21.1

11.2


Sept. 17 July 23


26.4
26.9
26.7
26.2
26.6
26.3
24.0
25.6
26.1
26.6
26.4
26.2

26.2


(mm)
396
67
222
245
167
93
62
126
129
402
230
219

2359


(m/sec)
0.86
1.14
0.92
0.53
0.53
0.42
0.67
0.55
0.55
0.61
1.17
0.88

0.74


(%)
84.8
80.5
82.5
89.7
87.4
86.5
76.8
77.1
77.5
81.2
81.1
82.6

82.3


(Cal/cm /day)
337
357
355
332
340
320
371
407
416
397
408
387


609

Oct. 23


Oct. 20


January
February
March
April
May
June
July
August
September
October
November
December


Year


Absolute
Daily
Reading
(Date)


1976.









If this is the case, high rates of dark respiration
could be occurring. This, rather than photores-
piration as was previously thought, may account
for some of the low yields of previous crops,
since daytime temperatures are not that high.
In addition, Table 2.1:1 shows that solar
radiation is not high enough to cause significant
photorespiration losses. On the contrary, low
solar radiation could be an important factor in
limiting yield potential during the rainy season.
Wind speeds do not seem to be too high, but
a seasonal effect is noted. The rainy season
shows more windiness than the cooler, drier
months. However, the monthly data results may
be misleading, since strong gusts of wind appear
in the drier season for short periods of time,
usually before a storm. These strong wind gusts
can cause serious yield reductions of some crops
due to plant lodging.
Yurimaguas is similar to many other places
in the tropics in that rainfall distribution may be
a serious problem even though the yearly or
monthly results show sufficient rainfall to grow
most crops the year around (Table 2.1:1).
If one studies the rainfall data shown in the
Annual Reports of 1974 and 1975, it can be
seen by the large 20% variability curves that
monthly rainfall distribution, especially during
the rainy season, varies greatly. The large varia-
tion in rainfall is not serious in terms of causing
plant water stress during the rainy season, but
excessive rainfall can be a problem. For ex-
ample, the daily rainfall distribution for January
1976 is shown in Fig. 2.1:1, where about
400 mm of precipitation was recorded. It rained
19 days out of 31 days in January. Even though


these are deep, well drained soils, such high
amounts and frequencies of rainfall make it ex-
tremely difficult for a farmer to plant and har-
vest his crops and to control weeds, diseases, and
insects. Crop growth and yields are also nega-
tively affected by low solar radiation and pro-
longed periods of water saturated soils.
Conversely, plant water deficit may also re-
duce yields even in the humid environment of
Yurimaguas due to poor rainfall distribution.
The 21-year rainfall records for the Yurimaguas
area show an average of 100 mm during the
driest months of June, July, and August (Annual
Reports 1974, 1975), but this can be extremely
misleading. For example, Fig. 2.1:1 shows that
most cf the rain falls during one thunderstorm.
Of the 93 mm of rain that fell in June 1976,
57.3 mm fell in one 24-hour period, and 78% of
the monthly total fell during the same 3-day
rainy period.
July was even worse than June. Severe water
stress was observed on all crops. Benites and
Naderman have shown (Sec. 2.4) that water
stress was probably one of the main factors con-
tributing to lower corn yields in the April plant-
ing compared to the September planting.
In conclusion, it can be stated that the cli-
mate at Yurimaguas and in other humid tropical
areas of the Amazon jungle basin, is, in general,
quite favorable to crop production. However,
the climate can also cause serious yield reduc-
tions if proper agronomic practices are not fol-
lowed. The climate strongly mandates the pest
control program required at Yurimaguas. For
example, fungus diseases start becoming a seri-
ous problem about three months into the rainy
















June, 1976


S2 4 6 8 10 1214 16 18 20 22 24262830
DAYS


Figure 2.1:1.


Rainfall distribution for January, June and July
1976, at Yurimaguas, Peru.


60

40

20


July, 1976





.1 I


i I I


40-









season and prohibit the planting of cowpea and
some soybean varieties. Toward the end of the
rainy season and the start of the drier season
(April through July) insects and birds become
the major pest problem. Weed control is also
closely related to the climatic pattern. At least
four cultivations are needed for adequate weed
control in crops grown during the rainy season,
whereas one, or at most two, weedings are
needed during the drier part of the year.


22 CONTINUOUS CROPPING EXPERIMENTS
J. H. Villachica and P. A. Sanchez
According to the plan of work outlined for
1976, rice was planted in early February 1976 in
crop sequence 1 (continuous upland rice) and
crop sequence 3 (rice-corn-soybean) in all
three chacras. The only exception was contin-
uous rice in Chacra 3, which was planted by
December 1975. The treatments and the level of
nutrients applied were the same as those de-
scribed in the 1975 Annual Report. By the mid-
dle of March 1976, some results on soil and
plant analyses were obtained. Results on the sat-
ellite experiments with lime, K, Mg, and micro-
nutrients were also available. All this data aided
a better understanding of what occurred in the
plots of continuous crops during the last 6-8
months of 1975.
It was evident that new fertility levels had to
be developed for continuous cropping in all the
chacras. The results of three years of research in
continuous cropping in Yurimaguas were show-
ing that the model that we had been using was
good only for no more than two years and that
our fertilization strategies, which were adequate


and economically sound in 1974, were found to
be inadequate in 1975 (Annual Report 1975).
Minor changes made in these fertilizer strategies
during 1975, i.e., raising the amount of N ap-
plied to the soil from 80 to 100 kg/ha, did not
significantly improve yields. These minor
changes were reported in the 1975 Annual
Report.
With these results, it was obvious that a
change in the research strategy for continuous
cropping was needed. We were studying mod-
erate to low fertilizer rates, even dropping some
of them, to lower the costs. However, yields ob-
tained during 1975 were also moderate to low.
By March 1976, the decision was made to
change our fertilization strategy to levels that
would ensure better yields. Satellite experiments
with S, Mg, K, lime and micro-elements were
very helpful for establishing these new levels.
The missing nutrient strategy was changed to
one of having a complete as a treatment and
then adding other elements to form the addi-
tional treatments (Table 2.2:1). Since contin-
uous upland rice had already achieved the goals
for which it was designed, it was changed for a
crop sequence with better agronomic and eco-
nomic possibilities. Thus, rice-soybean-peanut
was begun in the plots formerly used for contin-
uous rice. In March 1976, rice was growing very
poorly in all chacras and crop sequences, so it
was harvested and straw dry matter production
measured. At that time, it was too late in the
season to plant rice again, so the next crop in
each sequence (soybeans in new sequence 1,
corn in sequence 3) was sown. The results ob-
tained with each crop will be discussed later.







Table 2.2:1.


Description of the new treatments for the Rice-Soybean-Peanut and the Rice-Corn-Soybean systems
used after April 1976.


Treatment Amounts Applied (kg/ha)/


Former New
No. Identification Identification For Corn For Soybean

1 Check Check None None

2 Tilled check Complete plus mulch Same as treatment 5, plus Same as for corn,
standard mulch except with only 30 N

3 Complete, Complete plus kudzu Same as treatment 5, plus Same as for corn,
P residual and mulch standard kudzu and mulch except with only 30 N

4 Maintenance Lime, kudzu, and mulch Lime, standard amounts of Same as for corn
kudzu and guinea grass

5 Complete Complete Lime, 160 N, 70 P, 125 K, Same as for corn,
30 Mg, 124 S, 3 Zn, 3 Cu, except with only 30 N
1 B, 0.1 Mo

6 Complete, Complete plus kudzu, Same as treatment 3, except Same as for corn,
K residual mulch and SCU as N that SCU was used as N source, except that no N
source instead of common urea was applied

7 Half complete High complete 1.5 times the amount of NPK Same as for corn,
applied in 5, and twice the except with only 30 N
standard amounts of kudzu
and mulch


-/The amounts of lime applied were equivalent to 1.5 times the exchangeable acidity in each replication tested
individually; this varied from 1/4 to 2 tons/ha. Standard amounts of kudzu incorporated refer to 1 kg fresh
kudzu/m2 (30% dry matter) and mulch refers to 1 kg of fresh guinea grass (26% dry matter)/m2.










Changes in treatments and the amounts of
fertilizer and amendments applied are presented
in Table 2.2:1. The non-tilled check was main-
tained, and the tilled check was fertilized and
mulched (treatment 2). The complete fertilizer
level was higher than the previous complete and
also included Mg, Zn, Cu, B, and Mo, at opti-
mum rates as determined by the 1975 results.
Since soil analysis results cannot be obtained as
rapidly as desirable, there is a time lag for cor-
recting soil fertility changes. For this reason, a
high complete treatment was designed to be
used (treatment 7). Should there be a deficiency
of any element being applied, this treatment
should so indicate, giving higher yields than the
complete.
Lime and kudzu were incorporated to
10-12 cm depth when applied. Lime, as
Ca(OH)2, was applied 10-15 days before plant-
ing. Kudzu was incorporated the day before
planting. Mulch was applied the day following
planting. All the fertilizer P, K, Mg, Zn, Cu, and
B were broadcast at planting time and mixed
with the soil and the kudzu. Nitrogen applica-
tions were equally split at 18 days and 45 days
after planting. When SCU was used, it was ap-
plied at planting time. Molybdenum was applied
as a coating to the seeds. The fertilizer sources
used were urea (or SCU in treatment 6), simple
superphosphate, potassium chloride, magnesium
sulfate, zinc sulfate, copper sulfate, borax, and
ammonium molybdate. A foliar application of a
commercial formulation of micronutrients was
made at 15 and 50 days after planting for soy-
beans and 15 and 40 days after planting corn.


The rice-guinea grass system was continued
as described in the 1975 Annual Report. Thus, a
six-week interval cut was given to each plot, and
320-50-320 kg/ha/year of NPK were applied to
the complete plot. The N and K were split in
equal amounts after each cut, while P was ap-
plied once a year. Maintenance treatment con-
tinued receiving 120-20-90 kg/ha of NPK. Fer-
tilization strategies for all other treatments con-
tinued as before.
R ice-Soybean-Peanuts Sequence
As previously mentioned, rice growth during
early 1976 followed the same pattern described
for 1975 (1975 Annual Report). Thus, it was
not doing very well. For this reason, and for
time considerations, it was harvested at 60 days
of planting. After rice was cut, in April 1976,
soybeans (cv. National) were planted in the same
plots, but using the new treatments.
The results of soybean grain yield in Chacras
1, 2, and 3, obtained during 1976, are presented
in Table 2.2:2. Yields of soybeans ranged from
0.3 to 2.5 tons/ha. Highest yield was 2,725
kg/ha (41 bu/acre), excellent even by North
Carolina standards. When the former main-
tenance plots received lime, incorporated kudzu,
and guinea grass mulch, soybean yields increased
to about 1,500 kg/ha (treatment 4). When lime
and all the nutrients were added, with and with-
out kudzu incorporated or guinea grass mulch,
soybean yields were between 2,000 to 2,500
kg/ha (tmts. 3, 5 and 6). The yield of the high
complete treatment (number 7) was about equal
to that of the complete (treatment 5). This indi-
cated that the levels of fertilizers used with the
complete were sufficient.










Table 2.2:2. Soybean grain yields in Chacras 1, 2, and 3 for cropping sequence
1, as affected by soil treatments. Yurimaguas 1976. Average of
4 replications.



Treatment-/ Soybean grain yield (kg/ha)

No. Identification Chacra 1 Chacra 2 Chacra 3 Average

1 Check: 1 564 466 334

2 Complete plus mulch 1,985 2,081 2,572 2,213

3 Complete plus kudzu 2,386 2,089 2,179 2,218
and mulch

4 Lime, kudzu, and 1,287 1,554 1,554 1,455
mulch

5 Complete 2,703 2,208 2,725 2,546

6 Complete as 3 but N 1,761 2,319 2,695 2,258
as SCU

7 High Complete 2,368 1,939 2,542 2,283

Average per chacra 1,784 1,822 2,100

LSD.05 for chacras 320

LSD.05 for treatments 241

LSD 05 for treatment x chacra 417



-/Treatments as defined in Table 2.2:1









It is worth mentioning that the yield differ-
ences usually observed during 1974 and 1975
among Chacras 1, 2, and 3 were no longer pre-
sent with soybeans in cropping sequence 1 and
with corn in cropping sequence 3 (to be shown
later). This means that the differences in soil fer-
tility between the complete treatment in all
three chacras, so clearly present during the past
years, were overcome by the application of mod-
erately high rates of lime and fertilizers, with
very good yield responses. The main implica-
tions of this result are twofold. Firstly, yields
will be higher regardless of the age or use of the
chacra. Secondly, it suggests that all abandoned
or to-be-abandoned chacras with similar soils can
be recovered using this new fertilizer strategy,
with a high probability of obtaining very good
yields. Soybean yields in Chacras 1 and 2 as
compared with rice yields in the same plots are
shown in Fig. 2.2:1. Yield patterns on Chacra 3
are not shown, but they are similar to those of
Chacras 1 and 2. It can be observed that the de-
creasing slope of the response curves has been re-
versed. Soybean yields with the new complete
treatment in Chacra 1 were higher than any of
the last four crops of rice with the former com-
plete, even though soybeans do not have as high
grain yield potential as rice. Yields were also
higher than those obtained with soybean crop-
ping sequence 3, rice-corn-soybeans, in the
same chacras during 1975 (1975 Annual Re-
port). All these data indicate the successful rec-
lamations of these plots.
Peanuts, the next crop in the sequence, were
harvested at the moment of writing this report.


Preliminary evaluation of the data indicate that
the complete plots have yields between 4,000 to
6,000 kg/ha. These results also indicate that
good yields are still being obtained with the new
complete treatments.
A preliminary economic evaluation of the
cost of the new fertilizers and their profitability
is presented at the end of this Section 2.2.
R ice-Corn-Soybean Sequence
Results on corn yield planted in April 1976
are presented in Table 2.2:3. Results of rice dry
matter harvested before corn was planted are
not presented here. Table 2.2:3 shows that yield
of the check treatment was 0.4 tons/ha; when
the former maintenance plots were limed and
kudzu and guinea grass mulch were applied,
yields improved somewhat but were still low
(treatment 4). When the new complete treat-
ment (number 5) was used, yields increased
sharply up to 3.6 tons/ha. These yields are con-
sidered very good for the zone and for the grow-
ing period-110 days from planting to harvesting
time. Statistical analysis shows that the response
to the treatments was different between chacras,
except in treatment 7. The lower yield in
treatment 3 in Chacra 3 was due to a high per-
centage of lodged plants. In general, yields were
expected to be higher, but heavy winds at the
grain filling period produced a high number of
lodging plants which, it is believed, reduced the
yields. When these yields are compared to those
obtained in previous years, some interesting data
are obtained. The decreasing trends in yields in
all three chacras were reversed in 1976 (Fig.
2.2:2). From Table 2.2:3 one also notes that








Chacra I


4

3-


2
-o
0. -0

A


Oct.
72
1


Apr
73
2


Oct.
73
3


I R


Apr. Sep. Mar.
74 74 75
4 5 6


ICE


Sep.
75
7


Feb. Apr.
76 76
89
SSOYBEAN


Chacra 2


S- -
0- --o--So.


C, I I I I I I


Apr. Sep. Feb. Aug.
74 74 75 75
2 3 4 5


Feb.
76
6


RICE
Check
Complete
Maintenance

SOYBEAN
Check
Complete
Lime + Kudzu
+ Mulch


Apr.
76
7


I RICE SOYBEAN


PLANTING


DATE


Figure 2.2:1.


Rice and soybean yields in the new rice-soybean-peanut
sequence as a function of time. Mean of four replica-
tions. Yurimaguas, 1972-1976.


4


3

2


Oct.
73
I









Table 2.2:3.


Corn grain yields in Chacras 1, 2, and 3, cropping sequence 3, as
affected by soil treatments. Yurimaguas 1976. Average of 4 rep-
lications.


Treatment/ Corn grain yields (kg/ha)

No. Identification Chacra 1 Chacra 2 Chacra 3 Average


1 Check 1 243 846 363

2 Complete plus mulch 3,204 2,894 2,798 2,965

3 Complete plus kudzu 3,944 3,802 2,618 3,454
plus mulch

4 Lime, kudzu and mulch 493 679 1,392 855

5 Complete 4,054 2,971 3,805 3,610

6 Complete as 3, but N 4,321 3,524 4,019 3,955
as SCU

7 High complete 3,193 3,287 2,809 3,097

Average per chacra 2,744 2,486 2,612

LSD 05 for chacras 566

LSD 05 for treatment 376

LSD.05 for treatment by chacra 651


l/Treatments as defined in Table 2.2:1










o Check
* Complete
a Maintenance
(Lime+ Kudzu+
Mulch in
April,' 76,d


Oct.
1972
R


Apr. Jun. Nov. Apr. Aug. Nov. Apr. Aug.
--1973-1 --1974--1 H9754
C S S C S R C S


Chacra 2


Oct. Apr. Aug. Nov. Apr. Augt Apr.
1973 1974-1 1-1975- 11976
R C S R CS R C


Oct. Feb. AugTApr.
1974 11975--11976
R C SRC


PLANTING DATE, CROP AND
CROP SEQUENCE


Figure 2.2:2.


Grain yields of the rice(R)-corn(C)-soybean(s) cropping
system as a function of time after clearing. Mean of
four replications. Yurimaguas, 1972-1976.


Apr.
1976
C



acra 3


Ch










1976 corn yields for the complete fertilization
plots were higher than those obtained with corn
from 1972 to 1975.
Table 2.2:3 shows that best yields were ob-
tained with treatment 6, which had the same
levels of fertilization and soil amendments as
treatment 3, except that sulfur-coated urea
(SCU) was used as the N source instead of com-
mon urea. Average difference in yield was 501
kg/ha (14.5% more than treatment 3), indicating
the possibility that better N management could
still improve yields. As previously mentioned,
common urea was split into two applications for
corn, while N as SCU was applied only once.
Some N leaching loss can still be expected on
this sandy soil under the high rainfall conditions
of Yurimaguas.
The complete plus mulch treatment and the
high complete (treatments 2 and 7) did not yield
as well as the other treatments, even though
they were around the 3.0 t/ha yield level. The
failure of the high complete treatment to give
higher yields than the complete most likely indi-
cates that the complete treatment contained suf-
ficient nutrients.
Table 2.2:4 shows some of the chemical
properties on these plots sampled in December
1975. Main differences in chemical properties
among plots were due to pH and extractable Ca
and Al. These differences were corrected by in-
dividually liming each plot, according to its ex-
changeable Al. There were also differences in the
levels of available P and K, but all plots were low
in these nutrients, regardless of length of crop-
ping of the chacra.
Soybeans following corn were harvested at
the moment of writing this report. Preliminary


evaluation of the data indicate that soybean
yields were very low in the check plots, as was
expected. Soybean yields over 2,600 kg/ha were
observed with the complete treatments. These
results will be discussed in the next annual
report.
Rice-Guinea Grass Sequences
Results of the total amount of guinea grass
dry matter produced during seven consecutive
cuts in all three chacras are given in Table 2.2:5.
In general, yields were low, producing around
12 tons dry matter/7 cuts/ha in the complete
treatments in all three chacras. Differences with-
in the treatments were observed. The complete
and the complete with residual P yielded an
average of over 12 tons dry matter/ha/year,
which was twice the amount produced by the
checks and the complete, residual K. However,
this "high yield" was not comparable to those
obtained during 1973 for Chacra 1 (18 tons/ha)
and Chacra 2 (20 tons/ha). As was pointed out
in the 1975 Annual Report, these low yields
were, in part, due to changing the cutting fre-
quency from 8 to 6 weeks, which was recom-
mended by pasture specialists. Table 2.2:6
shows that soil exchangeable Ca and available P
in the complete treatment in Chacras 1 and 3
were about adequate and Al toxicity was not a
problem in October 1975. However, according
to the critical levels established at La Molina, the
amount of available K was low in Chacra 3
and medium in Chacra 1. It is also probable that
by October 1976 (a year after the sample was
taken), the amount of organic matter present in
Chacra 3 was lower and N availability was re-
duced. Soil samples are being analyzed to test
the hypothesis that N, Mg and K were also limit-
ing guinea grass yields during 1976.












Table 2.2:4. Topsoil (0-10 cm) chemical properties in the rice-corn-soybean plots in Chacras 1, 2, and 3, sampled in
December 1975. Analyzed at La Molina Experiment Station. (Mean of four replications)

Modif. 6N H2S04 Exchangeable
Treatment/ pH Olsen P K K Ca Mg Al Al Sat.
No. Identification C2 C2 C3 C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3 C1 C2 C3


1 Check

2 Complete plus mulch

3 Complete plus kudzu
and mulch

4 Lime, kudzu and
mulch

5 Complete

6 Complete plus kudzu,
mulch and SCU as N
source

7 High Complete


4.1

4.2

4.9


4.5

4.4

4.9


4.4 4.1 4.1


5.0 4.4 4.7

5.2 4.6 5.0



4.7 4.4 4.7


---ppm--

-- 1 3

-- 1 3

-- 2 7


---ppm---

25 39 50

28 39 44

57 104 75


-- 5 6 44 76 55


-- 6 9

-- 4 11


81 69

33 42


-- 4 6 38 60 51


----------------------

.13 .15 .15 .65 1.90

.13 .13 .14 .70 1.40

.19 .28 .18 4.95 5.00


me/1OOg -------------------

2.50 .4 .6 .7 2.70 2.20 1.75

1.80 .4 .5 .8 2.70 2.30 1.70

3.95 .6 .5 .8 .40 .40 .90


.16 .24 .15 1.40 2.40 2.80 .4 .5 .8 2.60 2.10 1.50


.17 .28 .15

.14 .14 .13


4.05 4.30

4.80 5.00


3.60

4.35


.5 .5 .8

.5 .5 .8


.60 .90 1.00

.65 .60 1.00


.14 .20 .15 3.10 3.10 3.05 .4 .6 .8 1.40 .90 2.05


I/Treatments as defined in Table 2.2:1


--- %

70 45

69 53

7 6


----

34

38

15 1


57 40 29


11 15

11 10


27 18 34









Table 2.2:5. Annual dry matter production of Panicum maximum in the rice-guinea
grass cropping system (sum of 7 cuts during 1976).


Treatmentl/ Chacra 1 Chacra 2 Chacra 3
17th to 23rd 13th to 19th 8th to 14th
No. Identification cuts cuts cuts Average

------------------ kg dry matter/ha -------------------

1 Untilled, unfertilized 3,300 4,358 7,975 5,211

2 Tilled, unfertilized 3,305 4,611 7,111 5,009

3 Maintenance 8,512 8,622 10,317 9,150

4 Complete 11,986 11,590 12,550 12,042

5 Complete, residual P 11,994 12,138 12,999 12,377

6 Complete, residual K 4,626 5,819 9,684 6,709

7 Half complete 9,357 10,443 10,455 10,085

Average per chacra 7,583 8,226 10,156

LSD.05 for chacras 1,170

LSD.05 for treatments 1,355

LSD.05 for treatments by chacras 2,346


-/Treatments are the same as those employed in 1975 (1975 Annual Report)










Table 2.2:6. Some soil chemical properties in the rice-guinea grass plots
sampled in October 1975. Analyzed at La Molina Experiment
Station. Average of 4 replications.


Chacra 1 Chacra 3

Tmt. 1 Tmt. 5 Tmt. 1 Tmt. 5
Soil Property Check Complete Check Complete


pH (1:2.5 in water) 4.0 4.9 3.8 5.1

P (0.5M NaHCO3 at pH 8.5), 6 33 3 11
ppm
K (6N H2S04), ppm 65 143 39 91

O.M. (Walkley and Black), % 2.3 2.3 3.2 4.6

Extr. Al (N KC1), me/1OOg 2.3 0.4 1.5 0.3

Exchangeable bases

Ca (N KC1), me/100g 1.4 4.0 2.4 5.8

Mg (N KC1), me/100g 0.6 0.4 0.4 0.4

K (N NH40AC), me/100g 0.09 0.12 0.08 0.22

Na (N KC1), me/lOOg 0.08 0.08 0.02 0.24

Al saturation, % 51 4 34 4










Calculations on nutrient uptake by guinea
grass during 1973 or 1974 showed that an in-
crease in the amount of nutrients added to the
soil was needed. Results of the last cuttings dur-
ing 1976 also indicated the need for this action,
i.e., Fig. 2.2:3 shows that the difference be-
tween the complete and the maintenance treat-
ments is, either minimal or non-existent. New
fertility levels and lime applications were started
in January 1977.
Some Economical Yield Data
Some draft calculations for fertilizer profita-
bility with the 1976 complete as compared with
1975 complete are given in Table 2.2:7. Yields
of 1975 complete were taken from the 1975
Annual Report, using the best averages in all
three chacras. Thus, the cropping sequence was
calculated to yield 1,500, 1,200, and 1,600 kg
of rice-corn-soybeans, respectively. Yields of
the non-fertilized checks were taken in average
from the three chacras. Rice yields for the 1976
complete were taken from the lime-K-Mg
microelement satellite experiment carried out in
a soil with initial similar chemical properties as
the check plots in Chacra 1. Soybean and corn
grain yields in the 1976 complete were taken
from the 1976 complete treatment data pre-
sented in Tables 2.2:2 and 2.2:3.
The data presented in Table 2.2:7 do not in-
clude inputs such as seeds, weeding, and insecti-
cides, which are considered to be equal for all
treatments. A higher hand labor requirement is
recognized to be needed at harvesting time, as
the yields increase, but is not taken into ac-
count. The table was made using the 1976 sub-
sidized prices for fertilizers. Results clearly


demonstrated the profitability of the new 1976
complete treatment. The profitability could be
even higher if dolomitic lime is used as the Mg
source.
All of this data can be used to fit the eco-
nomic models that are presently being developed
by Drs. Cate and Coutu, so a more integrated ap-
proach will be given in the near future.


2.3 FALLOW WITH KUDZU STUDY
D. E. Bandy
The traditional slash-and-burn system needs
a 20-year fallow for the recycling of nutrients to
regenerate an exhausted soil of the Amazon
jungle basin near Yurimaguas, Peru. This ex-
tended time period makes it impossible for any
type of a permanent agriculture system to be-
come established. If, for example, the fallow
period could be reduced to three or four years, a
small farmer could permanently farm a
five-hectare piece of land, rotating a one-hectare
cropping area per year with four hectares in dif-
ferent stages of fallow.
To investigate the possibilities of using a
shorter fallow period, a 5-year experiment was
initiated in 1975 at Yurimaguas using kudzu in-
stead of forest for the soil regenerator. Each
year a piece of previously farmed land, approxi-
mately 1200 M2, is placed into kudzu fallow so
that at the end of five years we will have a
chacra which has been in kudzu fallow for 4, 3,
2, and 1 years.
At the start of the fifth year, the kudzu will
be prepared for soil incorporation via several
methods as compared to a 20-year old forest
fallow parcel of land. The ultimate objective









CHACRA I


6-- Complete P
o--o Maintenance
*--- Check


S D F AJunA N D M M J J S O D J M A M JulA S
4973--- 1974 1975 b- 1976---
W-Cut every 8 weeks Ic- Cut every 6 weeks---


CHACRA 2


JunA S N J M MJunA S 0 D J F A MJul A S
1---1974 -- 1975 1976--- 1
KCut every 8 weeks' W,--Cut every 6 weeks-- ~


CHACRA 3




weeks


A J J AON D F M MJ J SO
e--r1975y6 1* --1976.-I
----Cut every 6 weeks---


Figure 2.2:3. Production of guinea grass cuts in the rice-guinea grass
system in Chacras 1, 2, and 3. Average of four replica-
tions. Yurimaguas, 1976.









Table 2.2:7.


Economic analysis of new fertilization strategy developed
in 1976 applied to the rice-corn-soybean rotation. Costs
in 1976 soles at Yurimaguas converted to US$ at the rate
of S/.45 per dollar.


Unfertilized 1974 strategy 1976 strategy


N-P-K
Mg-Cu-B-Zn-Mo
Extra lime (tons/ha)



Rice
Corn
Soybean


Fertilization (kg/ha/yr):

None 240-79-240
None None
None 1

Grain Yields (tons/ha):

0.5 1.5
0.3 1.2
0.4 1.6

Value of Crops (US$/ha/yr):


350-211-333
81-3-3-3-0.3
1



3.6
3.6
2.6


Rice
Corn
Soybean
Total Income


Expenditures (US$/ha/yr):


N, P, K fertilizers
Mg + micronutrients
Lime
Total fertilization
Cultural practices
Harvesting, threshing
Crop transport to market
Total costs



Net Profit (US$/ha/yr)
$ Profit/$ invested in
fertilizers and lime


128
61
157
346


383
245
629
1257


920
736
1023
2679


0
0
170
34
14
218


111
336
170
120
52
678


371
96
111
578
170
274
118
1140


Profit


579

1.72


1539

2.66










is to learn whether kudzu fallow can replace a
20-year old forest fallow, and if so, how many
years of kudzu fallow are needed.
Another kudzu fallow system was initiated in
1976 where a newly cleared chacra was inten-
sively farmed for one year, using very low rates
of fertilization, then placed one year in kudzu
fallow. After one year of kudzu fallow, the area
would again be intensively farmed for one year
using the same low rates of fertilization. This
experiment is expected to last for at least six
years, which would allow sufficient time to
study the changes in the physical and chemical
properties of the soil after three years of farm-
ing interspaced with three years of kudzu fallow.


2.4 VARIETIES AND SOME AGRONOMIC
FACTORS OF CORN PRODUCTION STUDIES
J. R. Benites and G. C. Naderman
Prior to the initiation of the intercropping-N
experiment, it was necessary to obtain consis-
tent information on the corn crop, since at the
early stage of the research in Yurimaguas corn
was identified as a problem crop. After evaluat-
ing corn yield data obtained in the different
experiments conducted from 1972 through
1975, it was decided to try those corn varieties
and hybrids obtained by the Corn Program of
the National Agrarian University (UNA) and
CIMMYT for tropical areas. Together with the
study of genetic material (considered to be the
first limitation) an attempt was made to learn
about the response of these varieties to fertiliza-
tion, plant population and other agronomic
factors.


Summary of Previous Corn Yields (1972-1975)
During 1973-1975, corn yields were ex-
tremely low. In 1973, the local variety "Cuban
Yellow," planted in a continuous cropping
experiment, only yielded an average of 0.5
tons/ha. Severe attacks of pests and diseases as
well as low levels of S, B, and Mo in the soil
were observed.
In 1974 the average yield was 1.94 tons/ha.
The corn variety Carimagua planted in the con-
tinuous cropping experiment, yielded an average
of 1.7 tons/ha and a maximum yield of 3.1
tons/ha using the following fertilizer rates:
80-44-66 kg/ha of N, P, K plus 0.5 kg/ha of B
and Mo, and 3.5 tons/ha of lime. These medi-
ocre yields were attributed to the low genetic
potential of the variety utilized and to pest and
disease problems. In 1974, the best average yield
was obtained with the variety Amarillo Planta
Baja (3.2 tons/ha), planted in the N x spacing
experiment, and a maximum yield of 4.0
tons/ha was obtained with the following fertil-
izer rates: 180-51-120 kg/ha of N, P, K plus
10 kg/ha of S, 0.5 kg/ha of B, 0.53 kg/ha of Mo,
and 0.9 tons/ha of lime.
In 1975 the mean yield was 2.0 tons/ha. The
variety PD (MS)6 planted in continuous crop-
ping experiment, yielded an average of 0.7
tons/ha and a maximum of 1.9 tons/ha. The
climatic conditions during this planting season
were not favorable, and the availability of soil
nutrients was low. A yield of 5.8 tons/ha was
obtained during 1975 with the hybrid PM-211
in the macro- and micronutrients experiment.









But the same hybrid planted in the same season
in the P-S interaction experiment, only reached
a mean yield of 0.7 tons/ha, and a maximum of
1.5 tons/ha obtained with the formula
120-53-100 kg/ha of N, P, K plus 60 kg/ha of S
and 1.4 tons/ha of lime.
In summary, all possible factors that could
have influenced corn yields during 1973-1975
did. These were genetic, agronomic, climatic,
and pests.
Corn Varietal Response to Liming and
Fertilization
Objectives and design. In earlier experiments
maximum yields generally have been associated
with the high fertility levels but there was no
certainty that genetic material with the highest
yield potential was used. This experiment con-
sisted of a test of 22 tropical varieties and
hybrids from the germplasm bank of the corn
program of the National Agrarian University.
Before treatment the first 15 cm of soil con-
tained 2.24 me and 3.03 me of Al and Ca + Mg,
respectively, per 100g of soil and 43% Al satura-
tion. Each variety was planted at two fertility
levels (indicated as lime-N-P-K in kg/ha):
1. 500-0-0-0
2.1500-180-66-83
Lime and P were applied during soil prepara-
tion 15 days before planting. The N was banded
beside the plants and was split into three equal
portions at 15, 30 and 45 days after planting.
Applications of K and Mg were made at 15 days
after planting. Atrazine was applied at 2 kg/ha
for weed control. The crop was planted April 21
and harvested after 102-114 days.


Results. Table 2.4:1 presents yields of the
varieties that reached more than 1.5 tons/ha, in-
cluding the local variety for comparison. Yields
of all varieties increased with fertilization and
liming; the varieties Amarillo Planta Baja,
PM-211, 1268 x 1273 (C11 x C16), and
Tuxpe6o Braquitico Blanco responded most to
fertilization and liming with yield increases of
46%, 56%, 55%, and 56%, respectively. The local
variety gave only a 17% yield response to liming
and fertilization.
The highest yield at both fertility levels was
obtained with the variety Amarillo Planta Baja.
This variety also gave one of the highest re-
sponses to liming and fertilization with a 46%
yield response. By comparing the yields of im-
proved varieties with the local variety in the
higher fertility treatment, it can be observed
that Amarillo Planta Baja, 1268 x 1273, PM-211
and PMS-264 were superior producing respective
yield increases of 113%, 88%, 74% and 70%.
During the experiment a strong insect, disease
and bird attack occurred and it was observed
(Table 2.4:2) that the highest proportion of
damage occurred in low-lime plots, although in
both cases the proportion was high. Table 2.4:3
shows some growth variables, such as plant
height, precocity and susceptibility to lodging.
The tallest plants were PMS-264 (2.83 m) and
the local variety Cuban Yellow (2.87 m). The
medium-height varieties were PM-211 (2.64 m),
and Hibrido Tropical (2.67 m). The shorter vari-
eties were Amarillo Planta Baja and Tuxpeno
Braquitico Blanco with 2.33 m and 2.18 m,
respectively. The hybrid PM-211 showed lodging










Table 2.4:1. Yield response of 10 corn varieties to lime and
Yurimaguas, 1976.


fertilization,


Corn grain yield

Low Lime Only Lime + Fert.


Yield re-
sponse to
lime and
fertiliza-
tion

%


---------- tons/ha--------


Comparison
with local
variety (both
rec'd fertil.)

% increase


POB II

PMS-264

Amarillo Planta Baja

PD(MS)6

PM-211

PMC-747

Hibrido Tropical

Tuxpeno Braquitico Blanco

1268 x 1273 (C11 x C16)

Cuban Yellow (local variety)


LSD.05

LSD.05

CV: 38%


1.73

1.85

2.09

1.79

1.39

2.03

1.51

1.01

1.52

1.51


2.60

3.07

3.86

2.48

3.14

2.88

2.59

2.32

3.40

1.81


Between varieties at the same fertility level:

For one variety at different fertility levels:


Variety


1.08

1.62


..___







Table 2.4:2.


Relationship between fertilization and corn ear
damage.


Ear Damage Low Lime Only Lime & Fert. Plots

Healthy ears (%) 38 46

Insect and disease damage (%) 36 33

Bird damage (%) 26 21


Drs. George Naderman (center) and Dale Bandy (right) confer with Ing.
Jose Benites regarding his experiment with N fertilization of corn, pea-
nuts and rice. Yurimaguas, Peru. March, 1977.









Table 2.4:3. Some phenotypic variables of corn in the variety x fertil-
ization experiment (mean of all plots).


Total Cumulative,
Plant lodged at heat units
Variety Height silking at silking
m %

POB II 2.55 1.53

PMS-264 2.83 5.31 1631

Amarillo Planta Baja 2.33 0.00 1521

PD (MS)6 2.47 3.04 1439

PM-211 2.64 8.71 1631

PMC-747 2.52 0.39

Hibrido Tropical 2.67 1.90

Tuxpeho Braquitico Blanco 2.18 0.00 1742

1268 x 1273 (C11 x C16) 2.81 2.66

Cuban Yellow (local variety) 2.87 3.03 1687


Cumulative heat units at silking stage were calculated according to the
formula of Gilmore and Rogers, (Max. temp OF + Min. temp OF -50 'F)

correction for temperature above 86 F was made.









susceptibility with 9% of the plants lodged at 73
days after planting and 50% at harvest time. In
contrast were the varieties Amarillo Planta Baja
and Tuxpeio Braquitico Blanco, which showed
zero lodging both at 73 days and at harvest time.
Finally, the earliest maturing varieties were
PD (MS)6 and Amarillo Planta Baja and the
latest maturing varieties were Cuban Yellow and
Tuxpefio Braquitico Blanco as determined by
cumulative heat units at silking.
Varieties and Plant Population Studies with
Corn
Objectives and design. The experiment on
varieties and plant population conducted in
1975 showed that as plant population was in-
creased from 55,000 to 66,000 per hectare,
yields tended to diminish, both in the fertilized
+ limed and low limed treatments. For this
reason in 1976, an experiment was installed,
which had 44,000 and 53,000 plants per hectare
as population treatments. Both populations were
planted at the same fertilization level
(160-66-125 kg/ha of N-P-K plus 18 kg/ha of
Mg and 2 tons/ha of lime). The most promising
corn varieties from the variety and fertilization
experiment were utilized, including the local
variety Cuban Yellow as check. Corn was
planted in September in Chacra IV.
The population of 44,000 was obtained by
planting rows of 0.90 with 0.25 m between
plants. The 53,000 population was obtained
with rows at 0.75 cm and 0.25 cm between
plants. Half of the N was applied 10 days after
planting with the balance at 30 days. Lime and P
were applied during land preparation prior to
planting. All K and Mg were applied together


with the first half of N. Harvest was 126 days
after planting.
Results. Table 2.4:4 shows that yields of all
varieties but one increased as the population in-
creased from 44,000 to 53,000 plants per
hectare. The varieties PMS-264, PD (MS)6 and
PMC-747 significantly responded to the higher
population with yield increases at 35%, 27%,
and 25%, respectively. However, the yield of
Tuxpeno Braquitico Blanco decreased by 69% as
plant population increased.
With respect to variety effect, Hibrido Tro-
pical had an exceptionally high yield of 6.49
tons/ha which greatly exceeded yields of the
other varieties. However, Hibrido Tropical and
other corn hybrids were badly affected during
the dry season, especially at the low fertility
level. Due to this consideration, for further
studies we preferred the composite variety
Amarillo Planta Baja which exhibited a tolerance
to dry season and wet seasons in low and high
fertility levels.
Planting Date Effect on Corn Grain Yield
The influence of planting date and associated
environmental factors is apparent by comparison
of the yields of two experiments previously re-
ported. The variety x fertilization study was
planted in April, and the variety x plant popula-
tion study was planted in September 1976.
Results of this comparison are presented in
Fig. 2.4:1. Yields of corn planted in September
were 43% greater than those of corn planted in
April. Varieties having the greater yield increases
from September planting were Hibrido Tropical,
PD (MS)6, PMC-747, POB-11 and PMS-264.










Table 2.4:4. Plant population effect on grain yield of 10 corn varieties
planted in September 1976. Yurimaguas.


Plant population, plants/ha


Variety


POB II

PMS-264

Amarillo Planta Baja

PD (MS)6

PM 211

PMC-747

Hibrido Tropical

Tuxpeno Braquitico
Blanco

1268 x 1273 (C11 x C16)

Cuban Yellow (local
variety)


40,000
Yield
compared
with
Grain local
yield variety

tons/ha % change

4.24 8.7

3.51 -10.0

4.14 6.2

3.74 4.1

4.57 17.2

4.17 6.9

5.94 52.3

5.34 36.9


4.07

3.90


4.4


Mean 4.30

LSD.05 Plant population: 1.34 tons/ha

LSD.05 Varieties: 0.95 ton/ha

CV: 15%


50,000
Yield
compared
with
Grain local
yield variety

tons/ha % change

4.81 20.3

5.42 35.5

4.72 18.0

5.09 27.3

5.02 25.5

5.52 38.0

6.49 62.3

3.16 -21.0


4.81

4.00


4.91


20.3


Yield
response
to
high
population

% change

11.9

35.2

12.5

26.5

9.0

24.5

8.5

-69.0


15.4

2.5












Planting Date
C-3 22 Apr.
mMI 20 Sep.


..... I II-II I -iI i L l -Iilil n -iln l |B ile J l Ilia It


oo0
azoo -

Z O0 O_
0 N
D -Z
X )


Figure 2.4:1.


The effect of planting date and associated environmental
factors on corn yields in Yurimaguas, 1976.


7.0


LSD.05


6.0


5.0-


c
a

C




(.
4-


4.0


3.0


2.0-


I.OF


-J
0<
or

II-


-i-i
zJ


i0
zj










Table 2.4:5 shows some of the average re-
sults of various climatic observations during the
growth of both crops. In September, the precipi-
tation more than doubled that of the April
planting; furthermore, between June and July,
51 cumulative days and more than 10 consecu-
tive days without rain were reported. It appears
that this dry period during the first planting
favored the increase of corn pests (Table 2.4:6),
especially during the flowering and maturation
process, which affected yields adversely. On the
other hand, during the September planting there
was sufficient precipitation with normal distri-
bution patterns.
Cumulative solar radiation was higher in
the September than in the April planting. This
factor may have influenced the yield-producing
potential per hectare in September because this
period received more solar radiation available for
photosynthesis.
All these data demonstrated that the planting
date had a large influence on corn yield. Good
varieties with an adequate level of fertilization
may fail if planted during the wrong planting
season.
Planting System, Row Spacing and Hilling
Objectives and design. The objective of this
experiment was to determine if the utilization of
hilling and a better distribution of plants in the
land could increase the efficiency of fertiliza-
tion, as well as to determine if they could reduce
plant lodging.
This experiment was installed in Chacra III.
The varieties Amarillo Planta Baja and the
hybrid PM-211 were utilized. The treatments for
each variety were row spacings of 0.90 or


0.75 m, planting systems of "drilling hill" (one
plant each 0.25 m) or "dropped hill" (three
plants each 0.75 m), and no, one or two hillings.
The combination of these factors gave 12 treat-
ments for each variety. For all treatments, the
following fertilization formula was utilized:
160-66-83 kg/ha of N-P-K plus 18 kg/ha of
Mg and 2 tons/ha of lime. Planting was accord-
ing to treatment. First and second hillings were
15 and 30 days after planting. Nitrogen was split
into two equal applications, and in each case be-
fore the hilling process. Harvest was 120 days
after planting.
Results. Table 2.4:7 shows the yields ob-
tained with the variety Amarillo Planta Baja. It
can be noted that the hilling practice increased
the yields from 4.90 tons/ha (without hilling) to
6.60 tons/ha (with one hilling), utilizing a row
spacing of 0.75 m. With a row spacing of 0.90 m
there were no differences in yields between one-
hilling and no-hilling, but with two-hillings there
was a significant increase in yields. There were
no differences found between planting systems
and row spacings.
The hybrid PM-211 had a mean yield lower
than that of Amarillo Planta Baja. None of the
factors being studied significantly affected the
yields of this hybrid and thus, the results ob-
tained with this hybrid are not presented in this
report.
Stalk-Doubled Over Effect on Corn Grain Yields
Objectives and design. During the drier season,
there is a high incidence of bird and insect dam-
age to corn. In the rainier season, damage is
caused by disease. In both cases, yields can be
reduced up to 50%. A common practice utilized










Table 2.4:5. Some climatic observations at the two growing periods.


Growing Period Growing Period
April 20 to September 20
Growing Parameter August 12 to January 24


Cumulative precipitation (mm) 489.1 1043.7

Cumulative solar radiation kCal/grl/cm-2 39.9 49.8

Average temperature- (OC) 25.2 26.5

Average maximum temperature (oC) 30.5 32.2

Average minimum temperature (oC) 20.9 20.5
1/
Average relative humidity- (%) 83.3 78.8

Average standard P.A.N. evaporation (mm) 3.4 2.5


the daily


-/Average temperature and average relative humidity are based on
averages from readings taken 07:00, 13:00 and 19:00 hours.








41


Table 2.4:6. Insect and disease damaged corn ears at two planting dates


Healthy Insect and disease Bird damaged
Planting date ears damaged ears ears

------------------------- % -------------------------

April 20 42 34.5 23.5

September 20 67 28.0 5.2


Mr. Jose Benites takes notes regarding his N fertilization experiment with corn, peanuts and rice.









Table 2.4:7. Planting system, row spacing and hilling effects on corn
grain yield of Amarillo Planta Baja. September, 1976.
Yurimaguas.


Planting system Mean
Row Hilling Row
Spacing Dropped Drilling Practice Spacing


cm


------ ton/ha


75








90







Mean
Row Spacing


No hilling

One hilling

Two hilling


5.54

6.60

5.18


4.25

6.60

6.16


4.90

6.60

5.67


Mean 5.77 5.67 5.72


No hilling 4.74 3.85 4.30

One hilling 6.37 3.64 5.01

Two hilling 5.99 5.84 5.92

Mean 5.70 4.44 5.08


No hilling 5.14 4.05 4.60

One chilling 6.49 5.12 5.81

Two chilling 5.59 6.00 5.80

Mean 5.74 5.06 5.40


LSD.05 Hilling Practice: 1.99

Method of planting and row spacing were not significant.

CV: 21%










by small farmers of the tropics in order to avoid
these problems is "stalk doubling." The objec-
tive of this experiment was to determine if this
is an agronomically sound practice and to deter-
mine which is the best time to perform it. The
stalks were doubled at four weekly intervals,
with the first beginning 20 days after silking.
This experiment was installed with a Cuban
Yellow seed planted in June. The plot received
only 50 kg/ha of N and 500 kg/ha of lime. The
stalk doubling was made below the principal ear.
Harvest was 41 days after silking.
Results. In Table 2.4:8 it can be noted that
stalk doubling did not affect the yields even
though stalks were doubled beginning 20 days
after the beginning of the silking stage. The
humidity percentage was 60.1% at the time of
the first stalk doubling, and 23% at harvest. It is
possible that the early utilization of this practice
could help corn avoid the consequences of ad-
verse climatic conditions which may favor pest
and disease infestation and also may reduce the
negative effect on shorter plants (rice, peanuts,
soybeans) that may grow intercropped with
corn. However, this supposition must be further
tested before a conclusive statement can be
made.
Tropical Corn Varieties and Hybrid Trials from
CIMMYT
Objectives and design. In August 1976 corn
seeds were received from CIMMYT which were
planted in September in Chacra IV, with the
purpose of expanding the information on
genetic material adapted to the tropics.
This experiment was fertilized with
160-44-83-18 kg/ha of N-P-K-Mg. The soil


was not limed since 1.5 tons/ha of lime had been
applied at the previous planting. Planting was at
a population of 50,000 plants per hectare
(0.90 m between rows and 0.60 m/3 plants).
Results.The varieties Mezcla Tropical Blanca,
(Ver. 181-Ant. Gpo. 2) 02, and La Posta were
the only ones that significantly out-yielded the
check variety Cuban Yellow (Table 2.4:9). The
varieties Tuxpe6o 1, Braquitico, Yellow H.E.02
and Tuxpeio Caribe-1 yielded less, but not signi-
ficantly than the local variety.
General Conclusions. Genetic material has a
great influence on corn yield. However, good
varieties with adequate fertilization may fail if
planted during the wrong planting season.
The corn variety Amarillo Planta Baja had
the best overall yields in the various trials. It
ranked first in the fertilizer and liming treat-
ments (3.86 tons/ha), as well as in the treatment
without fertilizer and low-levels of liming (2.09
tons/ha). Yields obtained in the dry season
(April planting) and the rainy season (September
planting) were favorable compared to those of
hybrids and other varieties which were badly af-
fected during the dry season. In addition, the
relative shortness of this variety (2.3 m) makes it
resistant to lodging. On the other hand, Amarillo
Planta Baja is an early variety, which silks in
50 to 58 days, and matures in 90 to 100 days,
making it possible to harvest with a 20-25%
grain humidity. Due to its earliness, this variety
can be planted up to three times a year, with a
potential grain yield of more than 10 tons/ha/
year.










Table 2.4:8. Effect of stalk doubling on corn grain yield of the Cuban
Yellow variety. 1976. Yurimaguas.


Date of
Doubling Days after silking Grain Humidity Grain Yield

% tons/ha

September 4 20 60.1 1.49

September 11 27 48.0 1.57

September 18 34 26.4 1.55

September 25 (harvest) 41 23.0 1.66


LSD.05:

CV: 30%


1.08









Table 2.4:9. Yield parameters of 22 CIMMYT tropical corn varieties. Sept-
ember, 1976. Yurimaguas.

Grain
Stover
Varieties Grain Stover Dry Matter Ratio
---------------- tons/ha -------------------


Tuxpeio-1 2.74 3.53 6.27 0.75
Mezcla Tropical Blanca 4.84 5.28 10.13 0.94
Blanco Cristalino-1 4.33 3.84 8.17 1.23
(Ver. 181 x Ant. Gpo. 2) Ven. 102 4.04 5.26 9.30 0.77
(Mix. 1 Col. Gpo. 1) Eto 3.65 5.99 9.63 0.62
Mezcla Amarilla 3.69 5.25 8.94 0.81
Amarillo Cristalino-1 4.01 6.50 10.52 0.62
Amarillo Dentado-2 4.17 4.55 8.73 0.92
Tuxpeho Caribe-2 4.82 5.46 10.28 0.91
Amarillo Dentado-1 4.54 5.71 10.24 0.83
Braquitico 2.75 5.61 8.36 0.48
Tuxpefo Caribe-l 3.03 4.14 7.17 0.99
Cogollero 3.67 4.46 8.13 0.84
Tuxpeno 02 3.71 5.48 9.19 0.69
(Ver. 181-Ant. Gpo. 2) 02 4.97 7.07 12.05 0.71
Yellow H.E. 02 3.30 5.02 8.05 0.66
White H.E. 02 3.17 3.54 6.71 0.89
La Posta 4.88 7.31 12.18 0.66
Eto Blanco 4.24 4.72 8.96 0.91
Ant. x Rep. Dominicana 3.92 2.95 6.87 1.39
Eto x Tuxpeno 4.51 5.16 9.67 0.88
Cuban Yellow Local 3.32 4.82 8.13 0.59

Mean 3.92 5.08 8.98 0.82
LSD.05 1.52 1.89 2.89 0.44
CV (%) 22.8 22.0 18.9 31.3









2.5 PHOSPHORUS AND SULFUR STUDIES
J. H. Villachica and P. A. Sanchez
Objectives and design. The basic idea for per-
forming this research was outlined in the 1975
Annual Report. First crop yields (corn) were re-
ported at that time. The same plots were used to
study residual effects of the lime, P, and S ini-
tially applied. Rice was used as the test crop,
and following its harvest, new rates of super-
phosphate and rock phosphate were applied
prior to soybean planting. Table 2.5:1 shows the
distribution of rice treatments. Treatments 1
through 15 were used to test the residual effect
of P, employing three and two rates of rock
phosphate (RP) and triple superphosphate
(TSP), respectively. Treatments 16 and 17 were
used to determine whether the S contained in
the superphosphate (SSP) would provide the S
needed by the plants. Treatment 18 was a check.
Treatments 19 and 20 were used to test if RP
applications prior to those of SSP would com-
pensate for the use of lime in this very acid soil.
All treatments were applied prior to corn plant-
ing, as reported in the 1975 Annual Report.
After corn was harvested, rice (cv. IR-4-2) was
planted on November 29, 1975, with no addi-
tional P, S, or lime. Following the rice harvest
of April 14, 1976, new levels of RP, TSP, SSP,
and lime were applied on April 25, as described
in Table 2.5:1. Soybeans (cv. XLM) were
planted on May 11, 1976. A basal application of
120 kg N/ha and 100 kg K/ha was applied for
rice. Soybeans received only 30 kg N/ha and
100 kg K/ha. Soybeans were harvested on
August 30.


Results. Table 2.5:1 also presents yields of
rice and soybeans harvested during 1976. Rice
yields with the first nine treatments, fertilized
with RP, but no lime, were very low. In all of
the first nine treatments except those of 7 and
9, yields were 0.5 ton grain/ha or less. Data pre-
sented in Table 2.5:2, with soil samples taken
before planting, indicate that these very low
yields were limited by the high amounts of ex-
changeable Al and the high percentage of Al sat-
uration in the soil. In fact, Al toxicity symptoms
were easily identified on rice plants growing on
these plots. These high Al contents were ex-
plained by the lack of lime application to the
soil and by the history of the field. All three rep-
lications were former bulldozed plots which re-
ceived no lime initially, neither from ash nor
from liming material. Data presented in Table
2.5:1 indicated that even though a high available
P content (Olsen method) was built up in the
soil, such as in treatments 7, 8, and 9, rice would
not grow adequately unless Al toxicity was neu-
tralized. As it will be discussed later, this was
noted also for soybeans.
Figure 2.5:1 shows the difference between
rice yields as determined by residual effects of
RP and those of TSP plus 1.4 tons lime/ha.
Yields of rice averaged over 1.3 tons/ha in the
treatments where residual effect of the two
levels of TSP was noted. Differences due to the
residual effect of S were not significant.
Rice yields on residual SSP plots (treatments
16 and 17) were similar to those on all residual
TSP plots, both with and without S. Thus, a re-
sponse to residual S was not evident in the rice










Table 2.5:1. Corn, rice, and soybean yields as affected by P sources and rates.
Average of three replications. Yurimaguas, 1975-1976.

Rate Prior to Rate Prior to
Corn Planting Soybean Planting Grain Yields.-
P P S Lime P Lime Corn Rice Soybean
Tmt Source -----kg/ha----- t/ha kg/ha t/ha -------kg/ha---------


26
26
26
52
52
52
208
208
208
26
26
26
52
52
52
26
52
0
26SSP+26RP
26SS+183RP


0
0
0
0
0
0
0
0
0
1.4
1.4
1.4
1.4
1.4
1.4
1.4
1.4
0
0
0


218
218
218
327
327
327
436
436
436
26
26
26
52
52
52
26
52
52
26SS+436RP
52SS+436RP


461 709


358


-Planting dates for corn, rice, and soybean were July 1975, November 1975,
and May 1976, respectively.


RP
RP
RP
RP
RP
RP
RP
RP
RP
TSP
TSP
TSP
TSP
TSP
TSP
SSP
SSP
NONE
SS+RP
SS+RP


0
0
0
0
0
0
0
0
0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
2.0
0
0


48
10
130
330
95
14
1,280
911
624
1,068
1,300
531
1,055
1,330
1,540
1,324
1,430
0
210
1,203


237
302
449
215
121
167
956
309
556
1,229
1,793
1,538
1,567
1,538
1,751
1,583
1,542
349
609
709


240
308
352
299
419
417
793
480
841
1,262
1,255
1,037
1,258
1,202
1,262
1,085
1,217
857
551
629


LSD.05










Table 2.5:2. Some soil chemical properties on P and S plots sam-
pled in November 1975. (Average of two replications)



Mod.
Olsen 6N H S04 1N KC1 extract. Al
Tmt P K pH 0.M. Al Ca Sat.


ppm


ppm


4.0
4.3
4.0
4.0
4.0
3.9
4.4
4.2
4.3
4.7
4.7
4.4
4.7
4.4
4.7
4.6
4.7
4.1
4.1
4.2


----me/100g----


2.5
2.2
2.5
2.4
2.6
2.1
2.5
2.8
2.5
2.7
2.4
2.2
2.0
2.3
2.8
2.5
2.3
2.4
2.5
2.6


2.1
3.0
2.9
2.6
2.9
3.1
3.1
2.2
1.7
1.0
0.7
2.5
2.1
2.3
0.5
1.3
0.9
2.2
2.4
1.4


0.7
1.8
0.9
1.3
1.0
0.8
1.2
1.4
1.8
3.0
2.9
2.3
2.5
2.7
3.3
3.1
3.2
1.5
1.6
1.5












2.0


0 30


60


INITIAL S APPLICATIONS
(6 months residual for rice)
(kg/ ha)


Figure 2.5:1. Effect of residual P and S on rice yields in Yurimaguas,
1976. Average of 3 replications. Triple superphosphate=
TSP; rock phosphate = RP.


P
(kg/ha)
as:

S120 TSP


-------'. 0. 60OTSP
//









480 RP
60 RP


0120 RP


1.6
(







0.8



0.4










yields. Neither did the following crop of soy-
beans show a response to the residual S of SSP.
Considering the low rice yields obtained
with the RP treatments, higher levels of RP were
used (Table 2.5:1) to determine if Al toxicity
problems could be alleviated in this way. Fifteen
days prior to soybean planting, RP or TSP plus
1 ton lime/ha were applied. No further additions
of S were made except where SSP was applied
with lime or with RP (treatments 16-20).
Soybean grain yields follow a similar pattern
to that described for rice (Table 2.5:1). Thus,
yields on the plots that received lime plus either
TSP or SSP were higher than those that received
only RP. However, soybean yields on plots 7
and 9, where a total of 644 kg P/ha as RP were
applied during the entire study, were not too
different from those of the plots that received
TSP or SSP, i.e., treatments 12 or 16.
Lack of difference between treatments 16
and 17 (those that received SSP) and treatments
10-15 (those that received TSP) indicated that S
was not limiting yields at this time. It should be
pointed out that in addition to Al, other limiting
problems in this experiment were believed to be
Mg deficiency and the low amount of N applied
for rice. Magnesium deficiency was proved to be
a limiting factor on soils of the area at the time
soybeans were planted, but it could not be cor-
rected because the only two available Mg fertil-
izers were Mg sulfate and K-Mg sulfate, both of
which are also sources of S.


2.6 MICRONUTRIENT RESEARCH
J. H. Villachica and P. A. Sanchez
Experiment 1. Responses to Lime, K, Mg and
Micronutrients.
Objectives and design. Preliminary results on
secondary and micronutrient studies reported in
the 1975 Annual Report showed a strong re-
sponse of corn and soybeans to lime and mag-
nesium and a good response of soybeans to
foliarly-applied micronutrients. Both studies
were continued to determine the residual effect
of lime and Mg and the effect of new applica-
tions of K and micronutrients. Both crop se-
quences (soybeans-rice-corn and corn-rice-
soybeans) were planted with rice (cv. IR-4-2) on
November 24, 1975, and harvested on April 7,
1976. Corn (cv. PM-211) and soybeans (cv.
National) were planted on April 23, 1976, after
rice was harvested. Soybeans were lost due to
herbicide residual effect. Corn was harvested on
August 23, 1976. Before each sowing of rice or
corn, K was applied in the amounts shown in
Table 2.6:1. A basal application of 150, 70, and
22 kg N, P, S/ha, respectively, was made in all
plots. Micronutrients were twice sprayed on the
leaves: at 45 and 67 days for rice, and at 20 and
40 days for corn. Residual effects of lime (ap-
plied May 23, 1975) and Mg (applied June 25,
1975) were studied. A composite rotable design
of treatments as presented in Table 2.6:1 was
used.









Table 2.6:1. Rice and corn yields as affected by the application of K,
microelements, and the residual effect of lime and Mg.
Yurimaguas, 19761/.

Treatment-/ Grain Yields

Micro- Corn-Rice-Soybean Soybean-Rice-Corn
nutrient Sequence Sequence
No. Lime K Mg Level3- Rice Rice Corn


t/ha --kg/ha--


83
83
166
166
83
83
166
166
83
83
166
166
83
83
166
166
0
125
125
125
41
208
125
125
125
125


----------------- kg/ha --------------


3112
3538
3224
4190
4117
4880
2731
3187
3336
4060
2964
4638
3603
3496
3244
4544
802
3670
3236
3726
3100
3384
3562
3502
3974
3586


2644
2882
1516
3462
822
2536
2940
3530
3094
4262
2948
4322
2552
4328
2912
2986
380
3662
2162
3796
2814
3804
2910
2787
2678
3270


1656
5239
148
3529
3224
4056
2075
4309
428
3926
148
3650
1524
4890
1192
2779
1
3281
138
5273
3529
3592
1617
3658
1278
5301


-Basal rate of 150 kg N/ha, 70 kg P/ha, and 22 kg S/ha was applied.
2-/Lime and Mg were applied on May 23 and June 25, 1975; K was applied be-
fore each planting. Micronutrients were applied two times as spray
during the growing period.
3/Micronutrient level 1 was: two sprays of a solution of 22 g zinc sul-
fate, 21 g manganese sulfate, 25 g iron sulfate, 7 g copper sulfate,
11 g borax, 1 g ammonium molybdate, and 43 g lime, all for 11 liters of
water, applied at a rate of 600 liters/ha. Levels 2, 3, and 4 of micro-
nutrients were 2, 3, and 4 times level 1, respectively.









Results. Yield response of rice to the dif-
ferent treatments and in both crop sequences is
shown in Fig. 2.6:1. A response to the residual
lime can be observed in the experiment where
rice was planted after soybeans. The response
was lower in the companion experiment. From
the data of Fig. 2.6:1, it seems that lime and K
were the most limiting factors for rice produc-
tion in this soil.
Table 2.6:2 presents some soil chemical
properties in soil samples taken before rice was
planted (corn-rice-soybeans sequence). It can
be observed that pH was 4.3 in the unlimed
plot, 4.6 where 2 tons lime/ha were applied five
months earlier, and 5.6 where 4 tons lime/ha
were applied also five months earlier. Similarly,
Al saturation decreased from 48% to 24% and
9%, respectively. This evidence indicated that
even though pH was low in the plots that re-
ceived 2 tons lime/ha initially, Al saturation was
not sufficiently high to cause problems for rice.
Yields of rice on the fertilized plots that were
limed initially with 2 tons lime/ha or more
averaged 3.5 tons grain/ha. This yield was con-
sidered excellent for upland rice growing in this
old abandoned soil with very low native soil fer-
tility.
Response to K of rice following corn exhib-
ited the same pattern as did the previous crop.
Thus, the maximum response was to 83 kg K/ha.
When rice was planted after soybeans, the
highest yield was observed with 125 kg K/ha. No
clear response to the residual effect of Mg was
found. Rice growing after soybeans (SAM ex-
periment) showed only small yield response to
residual Mg. Rice planted after maize (MAS ex-
periment) did not show response to residual Mg.


Rice yield response to micronutrients was
found only on those plots that had a previous
crop of soybeans. In these cases, the yield dif-
ference between the treatment that received
micronutrient level 2 and that not receiving
micronutrients was 984 kg/ha.
To continue studying the residual effect of
lime and magnesium, corn was planted next in
the sequence soybeans-rice-corn. Potassium
was applied before planting and micronutrients
were applied foliarly at 15 and 35 days at rates
given in Table 2.6:1. Corn (cv. PM-211) was
used.
Corn yields as influenced by treatment are
given in Table 2.6:1 and Fig. 2.6:2. A very dra-
matic response of corn to the residual effect of
lime can be observed in Fig. 2.6:2. Corn yields
were almost nil in the unlimed plots but fol-
lowed a linear response to the residual effect of
the lime initially applied. No yield plateau was
reached. The initially-applied 1 ton lime/ha level
which gave those good soybean yields eight
months earlier no longer provided adequate soil
conditions for corn growth. Yields over 4 tons
grain/ha were obtained only with the residual ef-
fect of 3 or 4 tons lime/ha applied at the begin-
ning of the experiment. The experiment was
limed on May 23, 1975, and then soybeans and
rice were grown successfully up to April 1976.
Thus, the residual effect of 1 ton lime/ha lasted
only about ten months. The residual effect of
2 tons lime/ha was noticeable, but reduced. This
fast depreciation of the residual effect of lime
can be explained by the high leaching conditions
in Yurimaguas which moved Ca into the subsoil
(Villachica, Ph.D. Dissertation, 1978) and on the
lime source used. Lime source used was calcium












I.-l


0 I 2 3 4
LIME APPLICATION (tons/ho)


I I
83 125


166
166


208
208


K APPLICATIONS (kg/ha)


9 18 27 36 I 2 3 4


Mg APPLICATION


(kg/ha)


LEVEL OF MICRONUTRIENT
SPRAY


Figure 2.6:1. Rice grain yields following soybeans (o--o SAM experiment)
or maize (o-o MAS experiment), as affected by the applica-
tion of K and micronutrients and the residual effects of lime
and Mg. Yurimaguas, 1976.










Table 2.6:2. Some soil chemical properties on the secondary and micro-
nutrient experiment with the corn-rice-soybean sequence.
Yurimaguas, October 1975.

1/ 21
Amounts Applied-/ Available-2 Exchangeable

Micro.
Tmt. Lime K Mg spray P K pH K Ca Al


T/ha


--kg/ha--


83
83
166
166
83
83
166
166
83
83
166
166
83
83
166
166
0
125
125
125
41
208
125
125
125
125


--ppm---


65
65
137
156
91
65
72
78
59
78
78
98
65
65
91

65
56
78
78
65
98
130
98
65
65


----me/0Og-------


4.4
4.7
4.8
5.2
4.7
5.3
4.4
4.8
4.8
5.0
4.6
5.2
4.6
4.8
4.6

4.4
4.8
4.3
5.6
5.0
5.0
5.1
4.9
4.9
4.6


.11
.11
.30
.30
.20
.12
.16
.16
.13
.14
.19
.22
.14
.13
.17

.16
.14
.14
.14
.15
.28
.35
.18
.11
.14


2.2
2.8
2.2
2.8
2.6
4.0
2.6
3.8
2.0
3.2
2.0
2.6
2.0
3.3
2.0

1.6
2.0
1.4
4.2
3.0
3.0
2.8
2.6
2.2
2.4


Amounts of amendments applied in June 1975. Micronutrients
foliar spray of micronutrients as explained in Table 2.6:1.


.70
1.20
.90
.20
.60
.20
1.10
1.00
.50
1.30
.40
.50
1.00
.90
.40

1.50
.90
2.00
.50
.50
.60
.40
.70
1.00
1.00


refers to


2/P was extracted with 0.5M NaHC03; K by 6N H2S04; exchangeable K by
IN NH4OAc at pH 7.0, and Ca and Al with IN KC1.





















0 I 2 3 4 41 83 125 166 208


LIME APPLIED


INITIALLY
( t/ha )


K APPLIED


9 18 27 36

Mg APPLIED INITIALLY
(kg / ha)


Figure 2.6:2.


2 3 4


LEVEL OF MICRONUTRIENT
SPRAY


Corn grain yields when planted after soybeans and rice,
as affected by K and micronutrient applications and the
residual effect of lime and Mg. Yurimaguas, 1976.


(kg / ha)










hydroxide of which 100% passed through a
2 mm sieve. Calcium hydroxide is known to be
very reactive in the soil and to have a short re-
sidual effect.
The next most limiting factor for corn grain
yield was micronutrients. Fig. 2.6:2 shows that
when micronutrients were not applied, corn
grain yields were slightly over 1 ton/ha, and with
the application of two foliar micronutrient
sprays, increased up to 5 tons/ha. That corn re-
sponded more dramatically to micronutrients
than did soybeans could be due to differential
crop species response and to a decrease in the
amounts of micronutrients originally present in
the soil. Thus, it is expected that when the soil is
under continuous cropping, micronutrient re-
sponses or deficiencies will be bigger after sev-
eral crops have been harvested.
No corn response was observed between 42
to 208 kg K/ha. This result, when compared
with those obtained in the first crops, suggested
that K was not a limiting element in this range
of application, although it was found in very low
levels in the soil (0.15 me K/100 ml). Magne-
sium residual effects were more limiting than K.
Yields of corn increased up to 3.1 tons grain/ha
with the residual effect of 18 kg Mg/ha. Soils
and plants have been sampled, and chemical
analyses are being performed. These data will
help to explain some of the responses observed.
A very important conclusion drawn from
these experiments is that 1 ton lime/ha did not
last more than ten months; 2 tons lime had a
little higher residual effect, but yields were
lower than those obtained with 3 tons lime/ha.
The best yield results for all crops were obtained


with 4 tons/ha lime as Ca(OH)2. For practical
considerations and for a 13-month cropping se-
quence of soybeans-rice-corn or any combina-
tion thereof, an initial application of 3 to 4 tons
lime should be considered. Since the residual ef-
fect of lime is lost so quickly, soil acidity should
be checked at least once a year in order to con-
sider application of additional lime. It was also
pointed out that Mg and micronutrients became
more limiting after two crops had been removed
from the field. These data partially explained
the rapid yield decline in the continuous crop-
ping experiments. It also was suggested that
yields in the continuous cropping experiments
would not have been improved as well this year
if only the new levels of lime and NPK were ap-
plied. Magnesium and micronutrients were
needed also. The need for the study of new lim-
ing materials that carry Mg and will have higher
residual effects is emphasized.
Experiment 2. Soybean Responses to Lime, Mn,
B and Mo.
Objectives and design. Soybean response to
micronutrients was observed in the experiments
conducted during 1975 and early 1976 in an old
abandoned field (1975 Annual Report). How-
ever, all micronutrients were applied as a foliar
spray. There was no information on which of
the elements was or were responsible for the in-
crease in yields. Soybeans growing during 1975
in Chacra 3 showed symptoms that resembled
Mn deficiency. Foliar analysis of soybean sam-
ples taken from this field indicated low levels of
Mn, B, Fe, Mg, and Ca in the leaves. For this rea-
son, a portion of Chacra 3 that was burned in
1974 and then abandoned again was cleared and










planted with soybeans (cv. XLM) in July 1976.
Five levels of lime, Mn, B, and Mo were studied.
The amounts of nutrients studied are presented
in Table 2.6:3.
Results. Table 2.6:3 and Fig. 2.6:3 present
soybean grain yield as affected by the applica-
tion of the different treatments. There was a re-
sponse to 1 ton lime/ha as soybean yields in-
creased from 1.5 ton/ha to 2.5 tons/ha (Fig.
2.6:3). No further response was found to addi-
tional lime applications up to 4 tons lime/ha.
This result differed somewhat from that re-
ported last year in the secondary and micronu-
trients study, where soybeans were reported to
respond up to 2 tons lime/ha. This could be ex-
plained by the low Al saturation of the soil in
Chacra 3, possibly due to some liming effect
from the ash (1974 Annual Report).
No positive response was observed to either
foliar Mn applications or Mo seed treatment, in-
dicating that both elements were present in ade-
quate amounts in the soil or that some other
factor was more limiting to yields. With respect
to B, soybean grain yields increased about 0.5
ton/ha when the first 0.5 kg B/ha were applied.
However, when additional 0.5 kg B/ha rates
were applied, soybean yields dropped to those
of the zero B level. Research in Georgia on sim-
ilar soils has indicated B toxicity to soybeans at
rates greater than 1 kg/ha.
Additional treatments of soil-applied Zn and
foliar applications of Fe were used to test the re-
sponse of soybeans to these elements. Table
2.6:3 shows that there was no response to either
one of these treatments (treatments 27 and 28).
However, when Cu was not applied as basal


(treatment 17), soybean yield was only 1.5
ton/ha, even though all other micronutrients
were applied. This result agreed with that found
in greenhouse experiments and reported in the
1974 Annual Report that Cu is limiting crop
yields in soils of Yurimaguas.
In summary, the evidence indicated that in a
newly cleared and burned chacra that has not
been cropped, Mo, Mn, Zn, and Fe were ade-
quately supplied to the plant. Boron seemed to
be needed in low amounts (0.5 kg B/ha), and ap-
plications of 2 kg Cu/ha were also necessary.
Experiment 3. Peanut Response to Cu, Mn, B
and Mo.
Objectives and design. Secondary and micro-
nutrient studies reported in 1975 showed a soy-
bean response to foliar applications of microele-
ments. The soil in which soybeans were grown
was a very low fertility soil from an old aban-
doned pasture. No beneficial effect of ash was
expected here. As previously emphasized, the
experiments with foliar micronutrients were de-
signed only to detect whether there was re-
sponse to microelements. No information was
obtained at that time with respect to which
micronutrient was deficient and what should be
the amount to be applied to the soil.
Peanuts were incorporated into the crop se-
quences being studied in continuous cropping
experiment, since they have a high cash value
and are very promising in the area. However, in
almost all of the experiments in which peanuts
were studied, plants were characterized by a
high number of empty pods at harvesting time.
Empty pods are known to be one of the symp-
toms of B deficiency. Chemical analysis indi-









Table 2.6:3.


Soybean grain yields as affected by lime, Mn, B and Mo
applicationsl.


Amounts Applied
Soybean
Tmt. Lime Mn B Mo Remarks2/ Yield


T/ha kg/1000 1/ha


0.5
0.5
1.5
1.5
0.5
0.5
1.5
1.5
0.5
0.5
1.5
1.5
0.5
0.5
1.5
1.5
1.0
1.0
1.0
1.0
0
2.0
1.0
1.0
1.0
1.0
1.0
1.0


kg/ha g/kg
seed


0.5
0.5
0.5
0.5
1.5
1.5
1.5
1.5
0.5
0.5
0.5
0.5
1.5
1.5
1.5
1.5
1.0
1.0
1.0
1.0
1.0
1.0
0
2.0
1.0
1.0
1.0
1.0


1.5
4.5
4.5
1.5
4.5
1.5
1.5
4.5
4.5
1.5
1.5
4.5
1.5
4.5
4.5
1.5
3.0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
0
6.0
3.0
3.0


Minus Cu








Plus Zn
Plus Fe


kg/ha


2333
1845
2591
2493
2602
2426
2941
2131
2808
2283
2823
2720
2051
1767
2230
2567
1587
2190
1535
2758
2420
1545
2182
2233
2257
2667
1965
2000


/A basal application of 70 kg P/ha, 102 kg K/ha, 30 kg Mg/ha, and 2 kg
Cu/ha was made.
-/Four kg Zn/ha and 0.5 kg Fe/1000 1/ha were applied in treatments 27
and 28, respectively. Iron was sprayed together with Mn at 30, 45,
and 55 days after planting.






















2 3 4


SOIL APPLIED LIME (t/ha)


0.5 1.0


FOLIAR APPLIEr


1.5 2.0

) Mn


(kg /1000 I /ha)


1 -


I I I I
0 0.5 1.0 1.5 2.0
SOIL APPLIED B (kg/ha)


0 No Cu


1.5 3.0 4.5 5.0
Mo SEED TREATMENT


(g / kg seed)


Figure 2.6:3.


Soybean yields as affected by lime, Mn, B, Mo applications.
Yurimaguas, 1976.










cated that B content in the soils of the Yuri-
maguas Experimental Station is very low and
not measurable in most of the cases.
For these reasons, it was necessary to deter-
mine the effect of five levels of Cu, Mn, B, and
Mo on soybeans (cv. National) and peanuts
(cv. Blanco Tarapoto) growing simultaneously
on two different experiments. Both crops were
planted in a field adjacent to the one where
secondary and micronutrient studies were con-
ducted. Thus, the soil was acid (pH 4.2), had
2.3 me AI/100 g soil, and was low in N, P, and
K. A central composite rotatable design was
used on both experiments. Peanuts were planted
on August 3, 1976, and harvested on November
18. Soybeans were planted also on August 3,
1976, but seedlings did not emerge well, due to
low seed quality. A new planting was on
September 3 and was harvested at the time that
this report was being written. Only results on
peanuts will be presented at this time. Treat-
ments and nutrient levels applied are presented
in Table 2.6:4.
Results. Results of peanut yields are pre-
sented in Table 2.6:4. It can be observed that
yields were generally over 4,000 kg/ha, which is
excellent for the zone. As indicated in Table
2.6:4, no N was applied to the plots. The idea
was to test peanut response to Mo in the pre-
sence of only the native soil N. Yields were re-
markably good, indicating that peanuts can be
grown with only the native soil N where the
proper Rhizobia inoculum is used. Fig. 2.6:4 in-
dicates that there was no response of peanuts to
copper applied to the soil or to manganese ap-
plied to the leaves. However, a high response to


boron was observed. As in the case of soybeans
described earlier, the biggest response was to the
first 0.5 kg B/ha. An additional response was ob-
served with the last 0.5 kg B/ha increment. This
last yield increment is difficult to interpret.
A response to Mo applied to the seeds was
also observed. The results indicated that when
1.5 g Mo/kg of seeds were applied as a slurry,
yields of peanuts increased from 3.8 tons/ha to
4.5 tons/ha, with no further increments with ad-
ditional Mo dosages. However, the high yield
with the check (3.8 tons/ha) also indicated a
good N fixation when Mo was not applied. A
survey of the roots of the peanuts showed that
nodulation in all plots was very good with most
of the nodules pink in color.
Additional treatments showed that when
none of the microelements (Cu, Mn, B, and Mo)
was applied, peanuts yielded only 3.0 tons/ha
(treatment 17). This was the same amount ob-
tained in the zero B plots. No peanut yield re-
sponse to the application of 4 kg Zn/ha was
noted. It will be remembered that corn also
failed to respond to Zn applied to the same soil
(1974 Annual Report).
From the last two microelement experi-
ments, it can be indicated that B, Mo, and Cu
deficiencies can be expected in Yurimaguas
Paleudults when they are continuously cropped.
No response to Zn or Mn was found with soy-
beans or peanuts. Initially reported low levels of
Mn in soybean leaves are thought to be related
to other nutrient deficiencies. The question re-
mains on how this response or lack of responses
will change after plants use the native micronu-
trients in the soil. Thus, the need for long-term










Table 2.6:4.


Peanut yields as affected by Cu, Mn, B, and Mo applica-
tions.


Amounts Applied


Tmt.


Cu Mn B Mo Remarks/


kg/ha


kg/1000
1/ha

0.5
0.5
1.5
1.5
0.5
0.5
1.5
1.5
0.5
0.5
1.5
1.5
0.5
0.5
1.5
1.5
0
1.0
1.0
1.0
0
2.0
1.0
1.0
1.0
1.0
1.0
1.0


kg/ha


0.5
0.5
0.5
0.5
1.5
1.5
1.5
1.5
0.5
0.5
0.5
0.5
1.5
1.5
1.5
1.5
0
1.0
1.0
1.0
1.0
1.0
0
2.0
1.0
1.0
1.0
1.0


g/kg
seed


1.5
4.5
4.5
1.5
4.5
1.5
1.5
4.5
4.5
1.5
1.5
4.5
1.5
4.5
4.5
1.5
0
3.0
3.0
3.0
3.0
3.0
3.0
3.0
0
6.0
3.0
3.0


Check








Plus Zn
Plus Fe


Peanut
Yield


kg/ha


4707
4375
5208
4083
4041
4333
4833
3875
3625
4750
4916
4250
3875
3625
4541
4333
3041
4381
4291
4416
4374
4458
3401
5291
3791
4458
4124
4042


-1A basal application of 2 tons lime/ha, 70 kg
30 kg Mg/ha was made. No N was applied.


P/ha, 102 kg K/ha, and


2/Four kg Zn/ha and 1 kg Fe/1000 1/ha were applied in each treatment.
Iron was sprayed together with Mn at 25, 36, and 50 days after
planting.




















I I
2 3


0.5 1.0


SOIL APPLIED


Cu (kg/ha)


FOLIAR APPLIED


(kg/1000 I/ha)


0 0.5


I I I I I I I
1.0 1.5 20 1.5 30 4.5 5.0


SOIL APPLIED B (kg/ha)


Mo SEED TREATMENT


(g / kg seed)


Figure 2.6:4.


Peanut yields as affected by Cu, Mn, B and Mo applications.
Yurimaguas, 1976.


1.5 2.0


Mn


3t


5F


~-o~o










micronutrient studies is evident. The data indi-
cate that in order to continue obtaining good
yields in the continuous cropping experiments,
the next micronutrients should be applied in the
following amounts per crop: 0.5 kg B/ha (as
Borax), 1.5 g Mo/kg seed (as ammonium molyb-
date), and 1 kg Cu/ha (as copper sulfate).


2.7 INTEGRATED CROPPING SYSTEMS
D. E. Bandy
In December 1976 an experiment was ini-
tiated in a new chacra (Chacra 5) that was re-
cently prepared for planting by the traditional
slash-and-burn method. The experiment is de-
signed to confirm or integrate results that have
been previously shown at the station.
The experiment used low levels of fertilizer
and lime since previous Annual Reports (1973
and 1974) have documented well that newly
cleared land has only enough nutrients in the
ash from the burn to produce fairly decent
yields for one or two crops, but not enough for
a whole year of intensive cropping. With the
proper selection of crop species and agronomic
practices it is possible to grow three crops a year
with very low levels of technical inputs and still
gain respectable yields. The Annual Reports of
1974 and 1975 have shown that a certain type
of intercropping, i.e., relay cropping, is best
suited for this area. Fertilizer rates were NPK at
0-35-66 kg/ha, Mg at 18 kg/ha, and the micro-
nutrients Cu, Zn, B and Mo at 3, 3, 1, and 0.1
kg/ha, respectively. In addition, lime at 650
kg/ha (CaCO3 equivalent) was applied. All soil
amendments were applied as basal applications
at the beginning of the experiment.


No nitrogen was applied since, from previous
experience, the ash should supply enough N for
the first crop. Succeeding crops were legumes or
non-nitrogen responsive crops (Fig. 2.7:1). Mag-
nesium was applied since it has been shown
(Annual Report 1975) that Mg deficiency was
probably one of the main reasons for the declin-
ing yields in the rotation experiment of Chacras
1, 2, and 3. Micronutrients were applied as insur-
ance since it was still not known for sure if one
year of cropping will use up all the micronu-
trients from the ash. It has been shown in
Annual Reports 1974-1975 that micronutrient
deficiencies of Mo and possibly Cu have ap-
peared after an area has been intensively
cropped for two to three years.
Lime was necessary to apply since these
Ultisols of the Yurimaguas soil series, are too
acidic and too Al saturated (Annual Report
1973) for most crops to produce any reasonable
yield unless the exchangeable Al has been neu-
tralized to a minimum of 30-40% Al saturation,
depending on crop tolerance to Al.
Preliminary results showed no negative ef-
fects of the low fertilizer and lime rates for rice,
cowpeas, soybeans, peanuts, sugar cane or
cassava. Corn did show nitrogen deficiency
symptoms. Complete yield data will be reported
in the 1977-1978 Annual Report.









CLEARING


CROP 1976
SYSTEM Dec.


Jan. Feb.


Mar. ADril


May June


1977
July


Aua SeDt.


Oct.


1978---
Nov. Dec. Jan. Feb.
I I I I I I I I I


I RICE
CASSAVA I KUDZU
S PEANUT I

CORN I


I PEANUT I


CASSAVA


I KUDZU 1


3 1 SOYBEAN


I PEANUT


CASSAVA


IKUDZU I


Figure 2.7:1. Schematic diagram of the integrated cropping experiment with low inputs begun in December, 1976.


SUGAR CANE IKUDZU
COWPEA COWPEA I


I_


_ _ __ __ __ __


--


I <


I



































Aerial view of small farms in area surrounding Yurimaguas, Peru.


Rice, peanut and corn fertilization study at the Yurimaguas Agricultural Experiment Station.










CERRADO OF BRAZIL
(Joint NCSU/Cornell Research)


Sr. Luis Souza-Lima (with moustache),a farmer in the Cerrado, talks with Dr. Elmar Wagner,
Director of CPAC, about current developments in the agronomic research developed by the
cooperative CPAC/Cornell/NCSU program at Brasilia. Una', Minas Gerais. March, 1977.










This report covers agronomic research con-
ducted cooperatively by scientists from Brazil's
Centro de Pesquisa Agropecuaria dos Cerrados
(CPAC), Cornell and North Carolina State
Universities. It includes field work conducted
from October 1975 through September 1976,
encompassing a full agricultural year with the
1975-1976 rainy season and the 1976 dry
season. Research conducted independently of
seasons is also reported.
This report will center on studies which
evaluated effects on crops of residual lime, Ca
and Mg downward movement, residual P,
residual Zn, K and Mg fertilization, and N fer-
tilization. Also discussed are crop species and
varietal tolerances to Al toxicity and low
available P, effects of P, lime and Si on soil
properties and plant growth, and an outreach
study of Cerrado soil properties.
Unless otherwise specified, all field experi-
ments were conducted on a clayey Dark Red
Latosol (Typic Haplustox, fine, kaolinitic,
isohyperthermic) located on a second erosion
surface at CPAC near Brasilia. Properties of
this soil were described in previous Annual
Reports and are typical of acid Oxisols of
tropical savannas. Generally speaking, these
soils are well-drained, relatively deep, acid, low
in organic matter, P, K, Ca, Mg, with a rela-
tively high P retention capacity. These Oxisols
are not as susceptible to soil compaction as are
the sandier Ultisols of the Amazon Jungle.


3.1 CROP WEATHER
W. Espinosa and M. Jarreta Junior
Meterological data for the 1975-1976
agricultural year at CPAC are given in Table
3.1:1. Average values for 35 years at nearby
Formosa are presented in Table 3.1:2.
The temperature the morning of July 7,
1975, at CPAC was unusually low (40C) as a
consequence of a cold wave which covered the
southern part of Brazil, causing great agricul-
tural losses, particularly in the state of Parana.
Precipitation during this year (1243 mm)
was considerably lower than the average of
1580 mm, due to reduced rainfall in the
months of December, January, March and
April. Four dry spells (veranicos) occurred as
shown in Fig. 3.1:1.
Fig. 3.1:2 shows the 1975-1976 meteoro-
logical water balance for CPAC using Class A
pan evaporation. For comparison, the water
balance based on solar radiation calculated
according to Hargreaves method and using
35 years of data collected at Formosa is pre-
sented in Fig. 3.1:3.


3.2 RESIDUAL LIME EFFECTS
A. RESIDUAL EFFECTS OF LIME ON
THE CLAYEY DARK RED LATOSOL
E. Gonzalez, E. Lobato and W. Shares
The effect of liming acid soils is usually
expected to last for several years. It is also
expected that this effect will be shorter in the










This report covers agronomic research con-
ducted cooperatively by scientists from Brazil's
Centro de Pesquisa Agropecuaria dos Cerrados
(CPAC), Cornell and North Carolina State
Universities. It includes field work conducted
from October 1975 through September 1976,
encompassing a full agricultural year with the
1975-1976 rainy season and the 1976 dry
season. Research conducted independently of
seasons is also reported.
This report will center on studies which
evaluated effects on crops of residual lime, Ca
and Mg downward movement, residual P,
residual Zn, K and Mg fertilization, and N fer-
tilization. Also discussed are crop species and
varietal tolerances to Al toxicity and low
available P, effects of P, lime and Si on soil
properties and plant growth, and an outreach
study of Cerrado soil properties.
Unless otherwise specified, all field experi-
ments were conducted on a clayey Dark Red
Latosol (Typic Haplustox, fine, kaolinitic,
isohyperthermic) located on a second erosion
surface at CPAC near Brasilia. Properties of
this soil were described in previous Annual
Reports and are typical of acid Oxisols of
tropical savannas. Generally speaking, these
soils are well-drained, relatively deep, acid, low
in organic matter, P, K, Ca, Mg, with a rela-
tively high P retention capacity. These Oxisols
are not as susceptible to soil compaction as are
the sandier Ultisols of the Amazon Jungle.


3.1 CROP WEATHER
W. Espinosa and M. Jarreta Junior
Meterological data for the 1975-1976
agricultural year at CPAC are given in Table
3.1:1. Average values for 35 years at nearby
Formosa are presented in Table 3.1:2.
The temperature the morning of July 7,
1975, at CPAC was unusually low (40C) as a
consequence of a cold wave which covered the
southern part of Brazil, causing great agricul-
tural losses, particularly in the state of Parana.
Precipitation during this year (1243 mm)
was considerably lower than the average of
1580 mm, due to reduced rainfall in the
months of December, January, March and
April. Four dry spells (veranicos) occurred as
shown in Fig. 3.1:1.
Fig. 3.1:2 shows the 1975-1976 meteoro-
logical water balance for CPAC using Class A
pan evaporation. For comparison, the water
balance based on solar radiation calculated
according to Hargreaves method and using
35 years of data collected at Formosa is pre-
sented in Fig. 3.1:3.


3.2 RESIDUAL LIME EFFECTS
A. RESIDUAL EFFECTS OF LIME ON
THE CLAYEY DARK RED LATOSOL
E. Gonzalez, E. Lobato and W. Shares
The effect of liming acid soils is usually
expected to last for several years. It is also
expected that this effect will be shorter in the










This report covers agronomic research con-
ducted cooperatively by scientists from Brazil's
Centro de Pesquisa Agropecuaria dos Cerrados
(CPAC), Cornell and North Carolina State
Universities. It includes field work conducted
from October 1975 through September 1976,
encompassing a full agricultural year with the
1975-1976 rainy season and the 1976 dry
season. Research conducted independently of
seasons is also reported.
This report will center on studies which
evaluated effects on crops of residual lime, Ca
and Mg downward movement, residual P,
residual Zn, K and Mg fertilization, and N fer-
tilization. Also discussed are crop species and
varietal tolerances to Al toxicity and low
available P, effects of P, lime and Si on soil
properties and plant growth, and an outreach
study of Cerrado soil properties.
Unless otherwise specified, all field experi-
ments were conducted on a clayey Dark Red
Latosol (Typic Haplustox, fine, kaolinitic,
isohyperthermic) located on a second erosion
surface at CPAC near Brasilia. Properties of
this soil were described in previous Annual
Reports and are typical of acid Oxisols of
tropical savannas. Generally speaking, these
soils are well-drained, relatively deep, acid, low
in organic matter, P, K, Ca, Mg, with a rela-
tively high P retention capacity. These Oxisols
are not as susceptible to soil compaction as are
the sandier Ultisols of the Amazon Jungle.


3.1 CROP WEATHER
W. Espinosa and M. Jarreta Junior
Meterological data for the 1975-1976
agricultural year at CPAC are given in Table
3.1:1. Average values for 35 years at nearby
Formosa are presented in Table 3.1:2.
The temperature the morning of July 7,
1975, at CPAC was unusually low (40C) as a
consequence of a cold wave which covered the
southern part of Brazil, causing great agricul-
tural losses, particularly in the state of Parana.
Precipitation during this year (1243 mm)
was considerably lower than the average of
1580 mm, due to reduced rainfall in the
months of December, January, March and
April. Four dry spells (veranicos) occurred as
shown in Fig. 3.1:1.
Fig. 3.1:2 shows the 1975-1976 meteoro-
logical water balance for CPAC using Class A
pan evaporation. For comparison, the water
balance based on solar radiation calculated
according to Hargreaves method and using
35 years of data collected at Formosa is pre-
sented in Fig. 3.1:3.


3.2 RESIDUAL LIME EFFECTS
A. RESIDUAL EFFECTS OF LIME ON
THE CLAYEY DARK RED LATOSOL
E. Gonzalez, E. Lobato and W. Shares
The effect of liming acid soils is usually
expected to last for several years. It is also
expected that this effect will be shorter in the










Table 3.1:1


. Meteorological data for the agricultural year 1975/1976,CPAC,
(150 36'S, 470 42'W, altitude 1010 meters).


Temperature (oC)
Precip- Evapor- Relative Solar
Month Max. Min. Avg. itation ation Wind Humidity Radiation


(m/s)

1.3

1.1

1.1

0.8

0.8

0.6


(%)

66.5

56.0

55.5

58.4

64.7

60.2

59.2

63.1

61.3

57.2

58.7

51.0


(cal/cm /day)

412.9

480.7



416.3

421.6

468.0

484.0

419.4


Te'cnico Anual, CPAC, 1976, Brasilia D. F.


July

August

September

October

November

December

January

February

March

April

May

June


23.7

27.2

28.5

28.3

26.4

27.0

27.8

26.6

27.4

27.9

26.7

26.7


12.5

14.8

16.6

17.3

17.6

16.8

16.7

17.8

17.7

16.9

15.3

13.6


(mm)

8.2

0

3.0

104.3

254.3

156.3

146.9

311.8

186.2

12.2

59.4

0


18.4

21.0

22.6

22.8

22.0

21.9

22.2

22.2

22.6

22.4

21.0

20.1


(mm)

170.5

213.6

242.2

169.9

141.2

166.5

167.8

132.7

146.3

155.8

134.6

166.9


Source: Relatorio






Table 3.1:2. Average of 35 years of meteorological data for Formosa,
tude 912 m).


GO (150 32'S, 47 18'W, alti-


Maximum
Average precipi-
Atmos- monthly station
pheric Avg. Min. Max. Relative precipi- in 24
Month pressure Temp. Temp. Temp. Humidity Cloudiness station hours Evaporation Insolation

(mm) (0C) (0C) (0C) (%) (1-10) (mm) (mm) (mm) (hrs)

Jan 909.5 22.0 17.8 27.4 80.2 7.7 271.9 100.7 73.2 180.5

Feb 909.6 22.1 18.0 27.8 80.8 7.7 204.2 85.0 63.7 159.3

Mar 909.8 21.9 17.9 27.6 81.5 7.5 220.6 92.5 67.1 186.8

Apr 910.9 21.5 17.0 27.6 77.3 6.2 42.7 77.8 75.3 222.2

May 912.2 20.1 14.8 27.0 71.4 4.8 17.0 41.8 97.8 270.3

June 913.6 19.0 13.1 26.4 66.0 3.8 3.2 18.0 113.0 279.9

July 914.1 18.9 12.6 26.3 59.4 3.4 5.5 25.2 141.3 278.0

Aug 913.2 20.7 13.7 28.4 49.6 2.7 2.5 45.8 188.3 303.2

Sept 911.5 22.8 16.2 30.1 51.7 4.0 30.0 63.6 189.2 236.2

Oct 910.1 22.9 17.8 29.2 66.0 6.7 127.1 103.4 138.1 200.7

Nov 908.8 21.6 18.0 27.4 79.3 8.3 255.3 107.5 75.2 142.7

Dec 908.8 21.9 18.1 26.6 83.0 8.5 342.5 124.9 60.8 125.1


Year 911 21.3 16.2 27.6 70.6 5.9 1,572.5 1,283.0 2,614.9


Source: Relatorio Tecnico Anual, CPAC,


1976. Brasilia D.F.













601


40


20





60


40F


5 15
I Jan.


Drought
I--- I


.l lI I,


5 15
-- Oct.


1 ..


I S


'25'
1975--


2"5 5' 1'5 25 5 1 '5
1975 I Nov.-I--- Dec.


Drought
I'---- I


.1. I


Drought
'- --*4


Drought
I-- -I


. 111


-_ I_ -__ I__ 'I_ -_ a S___ -_ S__ -


' II 1 1' 1 15 1 1 I '
25 5 15 25 5 15 25
1976 I ---- Feb. 1976 Mar. 1976--I


Figure 3.1:1. Daily rainfall at CPAC during the wet season 1975-1976.


20












0-0 Rainfall
o--0 Evaporation (Class A
pan)


600


Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May June


Figure 3.1:2.


Meteorological water balance for agri-
cultural year 1975-1976 for CPAC based
on class A pan evaporation.


Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May June

Figure 3.1:3. Meteorological water balance for 35 years
of data collected at nearby Formosa, GO,
based on solar radiation (according to
Hargreaves).










tropical region than in the temperate region be-
cause of more intensive climatic conditions of
high rainfall and high temperature. In the
humid tropical areas, leaching of basic cations
becomes important because it not only reduces
the residual effect of lime but affects the depth
below the zone of lime incorporation. This is
particularly important where subsoil acidity is
a problem for root development.
The first part of this discussion deals with a
soybean experiment conducted at the station
to test the residual effect of various lime levels.
The second part treats the movement and im-
plications of base movement in the profile
from plots limed & fertilized in different years.
Soybean Growth Under Various Residual
Levels of Lime
This residual study of lime was conducted
in the wet season 1973-1974 on an acid soil
where lime had been applied in November
1970 and Stylosanthes was planted during that
time. Soil samples taken before the application
of lime indicated that the soil was very acid
(pH around 4.6) with a high Al saturation in
the topsoil and subsoil (80 to 90 percent). The
amount of exchangeable Al was around 1.5
me/100 cc with the exchangeable Ca + Mg
around 0.2 me/100 in the top 30 cm of soil.
Different levels of calcitic limestone were in-
corporated to a depth of about 20 cm. These
levels of lime were effective in increasing Stylo-
santhes growth. The highest dry matter produc-
tion was obtained with 4, 6, and 8 tons of lime
[no statistical lime (1 ton)].Two harvests were


made before the residual study was established.
Tops were removed from the fields at each har-
vest. Grain yields of two varieties of soybeans
planted on these 3-year old plots are presented
in Table 3.2:1. As with the Stylosanthes, there
was a significant increase in yields of both vari-
eties with the first increment of lime. With
rates greater than 1 ton there were further in-
creases in yields, but this benefit was only
significant at the 6 ton level with the Viqosa
variety. The other variety, IAC-2, did not re-
spond as well at the highest level of lime. Over-
all, yields obtained in this study may be con-
sidered somewhat low for experimental condi-
tions. Both varieties showed an impressive vege-
tative and reproductive growth at all levels of
lime. Grain yields, however, were not as mark-
edly increased because of a long rainy period
which delayed harvest and reduced yields by
damaging some of the pods.
There are important features of the effect
of the various residual lime levels on soybean
yields. The increase in yields obtained with the
first increment of lime was considerable, in the
order of 800 kg/ha for both varieties. The in-
teresting point is that this increase occurred
when the soil was still very acid (Table 3.2:2).
The second soil sampling which was made after
the harvest of the soybean crop showed that Al
saturation was around 50 percent at the 0-15
cm depth and 63 percent at the 15-30 cm. This
indicated that these two varieties were rela-
tively tolerant to Al and responded well to
small additionsof lime.










Table 3.2:1.


Residual effect of various levels of
lime on grain yields (14% moisture)
of two soybean varieties in the LE
soill.


Previous
Lime rates

ton/ha

0

1

2

4

6

8


LSD05

LSD.5


Variety
Vigosa IAC-2

------- kg/ha --------

1095 1059

1902 1868

2137 1919

2139 2294

2695 2405

2729 2259


Lime = 545

Var. = 467


IValues are mean of 4 replications.










Table 3.2:2.


The residual effect of liming in the Dark Red Latosol
as measured by soil analysis. The first sampling was
done on December 1970, one month after lime applica-
tion. The second one in March 1974, after harvesting
the soybean.


Exchangeable
Lime Depth of
Levels Sampling pH Al Ca+Mg Al satur.


---me/1OOcc ---

First Sampling


0-20
20-40

0-20
20-40

0-20
20-40

0-20
20-40

0-20
20-40

0-20
20-40


4.2
4.1

4.5
4.3

4.5
4.4

4.7
4.4

5.1
4.7

5.3
4.6


1.76
1.37

1.22
1.32

1.22
1.25

0.82
1.17

0.32
1.10

0.10
1.05


0.32
0.27

0.77
0.29

0.95
0.37

1.57
0.37

2.85
0.63

3.60
0.72


Second Sampling


0-15
15-30

0-15
15-30

0-15
15-30

0-15
15-30

0-15
15-30

0-15
15-30


4.7
4.8

4.8
4.8

5.0
4.8

5.1
4.9

5.4
5.1

5.6
5.1


1.34
1.32

1.25
1.23

0.95
1.12

0.56
0.92

0.21
0.52

0.15
0.51


0.57
0.51

1.29
0.73

2.36
1.00

2.23
0.99

2.91
1.91

3.70
1.90


ton/ha










Another important aspect is that a further
response was obtained with the 6 tons of lime
after a plateau was reached at the 2 and 4
ton/ha level. The Al saturation at the 6 ton
level was less than 10 percent in the 0-15 cm
depth and around 20 percent in the 15-30 cm.
This is more in agreement with the results of
Soares et al., in 1974 on two Dark Red Lato-
sols where soybean yields increased sharply
with 5 tons/ha of lime, which had reduced Al
saturation to 10 percent. They, however, did
not have any rates less than 5 tons/ha. Spain
et al., also in 1974 found that soybeans respon-
ded to lime applications up to 6 tons/ha on an
acid Colombian Oxisol, but most of the re-
sponse occurred with an application of 2
tons/ha. The Vigosa and IAC-2 varieties yielded
an additional 800 and 550 kg/ha, respectively,
as lime rates were increased from 1 to 6
tons/ha. There was no further increase at the
8 ton level and with the IAC-2 there was a
slight reduction in yield. This increase in yields
with the 6 ton/ha rate represented a response
to a diminished Al saturation (about 10 per-
cent) or may have been due to greater availa-
bility of Mo. No Mo was applied with the soy-
beans, and the only Mo that had been applied
previously was before planting the Stylosan-
thes. Nutrient concentration of the trifoliates
of the two varieties (Table 3.2:3) showed Ca to
be in the sufficiency range of 0.36-2.00 percent
even in the check treatment. The concentration
of Ca increased with increasing levels of lime
but all were within the above range. The con-
centration of Mg may also be considered ade-


quate. Nitrogen concentration was increased
with the higher lime rates suggesting that nodu-
lation was more effective when soil acidity was
reduced further.
After three years of cropping there was a
considerable residual effect of liming in this
soil. Soil analysis showed that most of the Al
was still neutralized at the end of three years
where 6 tons of lime/ha were initially applied.
Results of the first sampling suggested that
lime was still reacting with the soil one month
after application.
Even though 1 ton of lime increased yields
considerably, it still was not sufficient for max-
imum growth and for efficient nitrogen utiliza-
tion. It was necessary to reduce Al saturation
to less than 10 percent to obtain the highest
yields in this experiment. This corresponded to
a soil pH of about 5.4 and is also the pH at
which Al was reduced to minimal levels in the
LE soil.
Cation Movement from Limed Plots
Natural downward movement of Ca and Mg
was studied on certain plots of the Dark Red
Latosol. These plots had been limed with cal-
citic limestone in different years and received
different fertilization practices. Results from
the oldest limed plots sampled for this partic-
ular study are reported in Table 3.2:4. This was
an experiment established in 1967, with Stylo-
santhes under different rates of lime and P. The
lowest level of P (33 kg/ha as triple superphos-
phate) applied in that year with no additional P
in subsequent years was selected in order to
avoid other sources of Ca besides the lime










Table 3.2:3. Nutrient concentrations of the uppermost trifoliate
in the late blooming stage of two soybean varieties
grown under various residual levels of lime in the
Dark Red Latosol. Wet season, 1973-74.


Lime
added Variety N P K Ca Mg Mn Zn


ton/ha

0

1

2

4

6

8



0

1

2

4

6


--)Jg/CC---


Vigosa

Vigosa

Vicosa

Vicosa

Vigosa

Vicosa



IAC-2

IAC-2

IAC-2

IAC-2

IAC-2


3.77

4.04

3.93

4.39

4.19

4.46



3.79

3.83

3.31

4.00

4.22


.19

.20

.19

.21

.21

.21



.19

.19

.16

.20

.20


1.9

1.9

1.7

1.8

1.7

1.6



1.9

1.9

1.8

1.8

1.7


.67

.95

1.01

1.17

1.19

1.27



.59

.63

.89

1.19

1.28


.27

.27

.27

.32

.28

.29



.23

.24

.24

.30

.28


121

87

76

71

70

57



134

103

95

93

66


177

116

95

94

96

87



178

133

124

87

57


4.04 .21 1.8 1.42 .32


------------ %


75 88


8 IAC-2










Table 3.2:4.


Soil analysis of limed plots (1967) in the LE soil
that were planted to Stylosanthes. Samples were
taken at 7.5 cm increments in April 1974.'


Exchangeable
Lime added Depth of
in 1967 sampling pH Al Ca Mg Al satur.


ton/ha

0









5


cm

0.0- 7.5
7.5-15.0
15.0-22.5
22.5-30.0
30.0-37.5
37.5-45.0
45.0-52.5
52.5-60.0
60.0-67.5
67.5-75.0

0.0- 7.5
7.5-15.0
15.0-22.5
22.5-30.0
30.0-37.5
37.5-45.0
45.0-52.5
52.5-60.0
60.0-67.5
67.5-75.0

0.0- 7.5
7.5-15.0
15.0-22.5
22.5-30.0
30.0-37.5
37.5-45.0
45.0-52.5
52.5-60.0
60.0-67.5
67.5-75.0


--- me/lOOcc ---


4.67
4.60
4.80
4.80
4.90
5.00
5.00
5.10
5.10
5.10

6.20
5.45
4.90
4.90
4.93
4.95
4.97
4.95
5.10
5.10

6.45
6.65
5.70
5.06
5.04
5.07
5.09
5.10
5.10
5.10


1.04
1.18
1.12
0.96
0.81
0.61
0.51
0.44
0.45
0.46

0.06
0.33
0.86
0.84
0.88
0.72
0.59
0.57
0.50
0.28

0.05
0.04
0.04
0.57
0.56
0.47
0.51
0.39
0.51
0.31


0.25
0.24
0.25
0.25
0.28
0.29
0.25
0.25
0.30
0.35

5.98
2.50
0.65
0.35
0.25
0.25
0.28
0.25
0.30
0.25

6.32
5.91
3.88
0.72
0.53
0.47
0.38
0.38
0.45
0.40


0.05
0.05
0.05
0.05
0.03
0.02
0.03
0.03
0.03
0.03

0.17
0.07
0.05
0.04
0.04
0.04
0.02
0.02
0.02
0.03

0.21
0.15
0.07
0.05
0.03
0.03
0.03
0.03
0.03
0.02


Values are mean of 2 plots. Each plot sample was a composite of
3 subsamples.










material. Thus, it is estimated that lime was the
only source of Ca since the triple superphos-
phate would have provided very little but a
uniform basal amount of Ca to the soil. The
only source of Mg was 200 kg MgSO4/ha also
applied in 1967 with no further application in
later years.
Not much movement of cations occurred
below the zone of lime incorporation with the
5 ton level. It is assumed that lime was not
physically incorporated below 15 cm depth. A
small rotovator was used to incorporate this lime
and good mixing with the soil was accomplished.
Some Ca seems to have moved into the 15.0-
22.5 cm depth, but insignificant amounts of Ca
moved below 22.5 cm. With the 10 ton level a
considerable amount of Ca moved into the
15.0-22.5 cm, a much lower quantity moved
below that zone into the 22.5-45.0 cm depth,
and insignificant amounts below 45.0 cm. For
all practical purposes, the effective depth of
movement was limited to 22.5 cm where most
of the Al was neutralized. Below that depth, Al
saturation was still high, being around 50 per-
cent, which may be toxic for many crops. The
data also showed that essentially all the Mg
applied as MgSO4 was lost, most probably by
plant uptake (there were 6 cuttings of the
Stylosanthes). Only a small portion was retained
in the limed zone by pH-dependent charges.
In a more recent experiment (Zn II experi-
ment) where high rates of lime were incor-
porated to about 20-25 cm in November 1972
and the soil sampled in April 1974, there was


marked downward movement of Ca to about
15 cm below the depth of incorporations
(Table 3.2:5). This caused the decrease of Al
saturation in the 30-45 cm zone from 70-75%
initially to about 50% or less within 11/ years
after liming.
Since no MgSO4 was applied, there was little
Mg in the profile. The Mg in the top cm came
mostly from the calcitic limestone. This was the
same material as that applied in the depth of
liming experiment.
In the Zn II experiment, several anions were
incorporated along with the limestone. These
included chlorides (from KCI), nitrates (from
nitrification of NH3 of the urea) and some sul-
fate (from ZnSO4). These anions may have en-
hanced Ca movement acting as the accompany-
ing ion in the leaching process. Work in South
Africa by Reeve and Sumner in 1972 reported
that heavy fertilization and high rates of lime
increased the rate of cation movement, but the
Ca had little effect on exchangeable Ca and Al
below a depth of 45 cm in a typical Natal Oxisol
after 14 years. Dolomitic limestone was applied
in the top 15 cm.
In the Stylosanthes study there was no source
of anions as in the Zn II experiment, and very
little Ca actually moved from the zone of appli-
cation. Besides the need of anions for cation
movement in the soil, a high rate of lime is also
important. The literature on this subject indi-
cates that movement occurred only at high rates
of lime, and this rate has been related to the
texture of the soil.









Table 3.2:5.


Soil analysis of limed plots (1972) in the LE soil
(Zn II experiment). Samples were taken at 7.5 cm
increments in April 1974.1


Exchangeable
Lime added Depth of
in 1972 sampling pH Al Ca Mg Al satur.


--- me/lOOcc ---


0.0- 7.5
7.5-15.0
15.0-22.5
22.5-30.0
30.0-37.5
37.5-45.0
45.0-52.5
52.5-60.0
60.0-67.5
67.5-75.0

0.0- 7.5
7.5-15.0
15.0-22.5
22.5-30.0
30.0-37.5
37.5-45.0
45.0-52.5
52.5-60.0
60.0-67.5
67.5-75.0

0.0- 7.5
7.5-15.0
15.0-22.5
22.5-30.0
30.0-37.5
37.5-45.0
45.0-52.5
52.5-60.0
60.0-67.5
67.5-75.0


7.68
7.65
7.44
5.62
4.98
4.83
4.73
4.54
4.46
4.41

7.02
7.35
7.15
6.12
5.07
4.97
4.80
4.75
4.52
4.50

7.15
7.30
7.35
6.60
5.10
5.10
4.75
4.60
4.55
4.35


tr.
tr.
tr.
0.06
0.62
0.67
0.63
0.65
0.63
0.65

tr.
tr.
tr.
tr.
0.67
0.68
0.63
0.61
0.63
0.90

tr.
tr.
tr.
tr.
0.64
0.67
0.70
0.74
0.76
0.74


8.13
7.45
6.88
4.38
1.38
0.59
0.38
0.35
0.30
0.25

6.95
7.50
7.25
3.70
1.21
0.76
0.45
0.43
0.35
0.30

6.02
6.13
6.35
4.73
1.09
0.94
0.39
0.30
0.30
0.25


0.12
0.08
0.07
0.07
0.05
0.02
0.03
0.04
0.04
0.03

0.13
0.13
0.08
0.07
0.03
0.03
0.03
0.02
0.03
0.03

0.18
0.14
0.10
0.08
0.07
0.04
0.03
0.02
0.03
0.02


Each rep-


ton/ha


Values are mean of 3 replications at each lime level.
location is a composite of 4 subsamples.










B. RESIDUAL EFFECTS OF LIME RATE
AND INCORPORATION DEPTHS
J. G. Salinas, E. Gonzalez, E. J. Kamprath and
P. A. Sanchez
A fifth crop of corn was grown during the
1975-1976 rainy season in order to continue
evaluating the residual effects of lime applica-
tions and changes in soil properties. The experi-
mental design and methodology has been
reported in previous annual reports. Besides
the evaluation of annual, cumulative and
residual effects of liming on the grain produc-
tion as well as its effects on the soil properties
to the depth of lime incorporation, a decision
was made to study the soil properties in terms
of downward movement of basic cations and
root development as deep root proliferation.
The N, P and K applications continued this
season with a broadcast application of
124 kg K/ha as KCI, a banded application of
44 kg P/ha as triple superphosphate (TSP) and
20 kg N /ha as urea followed by three side-
dressed applications totaling 200 kg N/ha as
urea. As in earlier experiments, the same corn
variety Cargill-111 was planted in 80 cm rows
at an approximate population of 50,000
plants/ha. The experiment was planted on
October 31, 1975, and harvested on
March 20, 1976.
Yields
Results of the fifth corn crop are shown
in Fig. 3.2:1. As in previous crops, significant
yield increases were produced by the residual
effect of only 1 ton lime/ha incorporated to


either depth. The yields from rates of 2 and
4 tons/ha at either depth were not significantly
different from the same depth at 1 ton/ha.
At 8 tons/ha, however, both depths of this lime
rate yielded significantly more than all lower
rates. This yield increase could be explained by
the very low Al saturation maintained over time
on the surface and subsurface. On the other
hand, the non-significant difference between
shallow and deep application at this highest rate
essentially was due to the fact that in the sub-
surface (15-30 cm) at the shallow application,
the Al saturation was quite low (less than 20%
Al saturation) which indicated no toxic effect
on root growth.
Effects on Soil Properties
The Table 3.2:6 shows the change in soil pH,
exchangeable Al and percent Al saturation in
samples taken after each crop harvest from May
1973 to April 1976. Soil pH at two depths for
all lime rates after each of five crops is shown in
Fig. 3.2:2. In general, the pH gradually de-
creased in both shallow and deep incorporations.
With time the pH values for both shallow and
deep placement of 1, 2 and 4 tons lime/ha de-
creased to similar values. Although there was a
decline in pH at the rate of 8 tons/ha incor-
porated to 30 cm depth, this high rate of lime
still maintained substantial residual effect after
five years. In addition, the pH values at
15-30 cm depth in shallow treatments showed
increases with time even though no lime was
applied at this depth.











(0-30


15cm)


ILSD05=0.67 tons / ha


2 4 8


IN 1972 (tons/ha)


Figure 3.2:1.


Corn yields of the fifth crop (1976) as
affected by lime applied in 1972. Brasilia.


0 I
LIME


APPLIED









Table 3.2:6.


Soil pH, exchangeable Al, and percent Al saturation of the five crops as affected by depth and rate
of lime applications in 1972.


Soil pH Exchangeable Al Al Saturation
Depth
of lime Lime Soil May Nov May Mar Apr May Nov May Mar Apr May Nov May Mar Apr
incorp. rate depth 1973 1973 1974 1975 1976 1973 1973 1974 1975 1976 1973 1973 1974 1975 1976

--cm-- ton/ha -cm-- --------- 1:1 H20 ---------- --------- me/100cc---------- ------------ % -------------

No Lime 0 0-15 4.7 4.6 4.5 4.4 4.2 1.10 1.03 1.14 1.41 1.48 71 72 68 78 78
15-30 4.7 4.5 4.4 4.3 4.1 1.16 1.01 1.18 1.25 1.25 68 68 73 81 71

Shallow 1 0-15 5.0 4.9 4.9 4.9 4.4 0.85 0.55 0.62 0.66 0.89 43 28 30 41 44
15-30 4.8 4.7 4.6 4.6 4.4 0.98 1.00 0.99 0.97 0.90 61 69 60 62 51
2 0-15 5.1 5.3 5.2 5.0 4.8 0.52 0.16 0.35 0.56 0.64 22 7 15 24 25
15-30 4.8 4.8 4.6 4.7 4.6 0.97 0.97 1.08 0.99 0.80 65 61 63 57 44
4 0-15 5.6 5.7 5.6 5.2 4.9 0.18 0.08 0.08 0.33 0.36 6 2 3 12 13
15-30 4.8 4.8 4.8 4.8 4.7 0.92 0.79 0.92 0.93 0.69 61 45 50 50 33 o
8 0-15 6.4 6.4 6.5 6.1 5.7 0.07 0.03 0.07 0.08 0.02 2 1 1 1 1
15-30 4.9 4.9 4.9 5.3 4.9 0.74 0.76 0.68 0.55 0.36 47 35 20 27 15

Deep 1 0-15 5.1 4.9 4.9 4.7 4.4 0.79 0.66 0.89 0.99 1.25 39 35 48 32 63
(0-30) 15-30 5.0 4.9 4.8 4.6 4.4 0.88 0.86 1.03 1.04 1.07 46 58 58 66 62
2 0-15 5.4 5.2 5.4 5.1 4.6 0.25 0.28 0.33 0.50 0.73 11 12 12 23 31
15-30 5.2 5.1 4.9 4.8 4.6 0.66 0.40 0.73 0.78 0.66 31 20 40 51 33
4 0-15 5.9 5.4 5.5 5.4 5.2 0.17 0.17 0.21 0.26 0.18 4 6 9 10 6
15-30 5.4 5.1 5.1 5.0 4.8 0.34 0.33 0.51 0.66 0.43 13 16 25 35 19
8 0-15 6.5 6.1 5.9 5.9 5.7 0.06 0.07 0.06 0.07 0.05 1 1 1 1 1
15-30 5.9 5.5 5.2 5.3 5.2 0.16 0.11 0.14 0.13 0.15 5 3 5 5 5







Shallow Placement
(0 15 cm)
0-15 cm Soil Depth

lime rate
(tons/ha)

8


Deep Placement
(0-30 cm)


- 0-15 cm Soil


Depth

lime rate
(tons/ha)


I I I I I


0 2 3 4 5


(1973)


(1976)


6 15-30cm Soil Depth



5- 8


4-


1 2345


(1973)


(1976)


-15-30cm Soil Depth


I I I I I
0 1 2 345


(1973)


(1976)


I I I I I I
I 2 3 4 5


(1973)


(1976)


CROP SEQUENCE


Figure 3.2:2. Residual effects of lime rates and depth of
incorporation on the soil pH at two depths
after each of five crops. Brasilia, 1972-
1976.


I I I I I


I
0.

(0










Perhaps a better picture of these differences
is given by consideration of change of percent Al
saturation. Fig. 3.2:3 shows a progressive de-
crease in percent Al saturation in the 15-30 cm
layer of shallow applications which was asso-
ciated with downward movement of basic
cations. Thus, five years after lime applications
in the Dark Red Latosol, the additional benefit
of deep incorporation of lime which was ob-
tained during the first three crops started to
decrease in the fourth crop and was almost
negligible after the fifth crop. However, from
the economical point of view, the superior
performance of deep application is still evident
since deep lime placement produced the same
yield with half the rate of lime as did shallow
application. It is important to remark that the
fifth crop was planted on the date in which the
probability was high to escape from a severe
"veranico" during the grain formation stage.
In addition, a severe veranico did not occur
during this wet season. The only slight drought
period within the 1975-1976 rainy season
occurred for 8 days at the beginning of January
1976, 65 days after planting this experiment and
which did not cause serious plant water stress
due to cloudiness and high humidity.
Cumulative and Residual Effects of Liming
The seasonal and cumulative yields of the
five crops are presented in Table 3.2:7.
Although there was no difference between
shallow and deep applications in the fifth crop,
the overall trend still showed that deep lime
application had a positive effect after five years.


From observation of the cumulative yields, one
notes equal yields from one-half as much lime
when incorporated to 30 cm as compared with
incorporation to 15 cm.
The residual effects of the original lime treat-
ments applied in 1972 are shown in Fig. 3.2:4.
These effects are expressed as percent of max-
imum yield relative to the highest absolute
yield which was always produced by 8 tons/ha
of lime incorporated to 30 cm. After five years,
1, 2 and 4 tons/ha lime at shallow and deep
incorporations produced similar yields.
However, the lack of differences between
shallow and deep placement might be atttribu-
table, in part, to the lack of natural drought
period in this wet season. The shallow incorpora-
tion of 8 tons lime/ha produced 90% of the
maximum yield and its residual effect was still
considerable. This experiment will be continued
by CPAC staff members in order to fully eval-
uate the residual effects.
Yields of the five crops expressed as percent
of the maximum yield (8 tons lime/ha incor-
porated to 30 cm) as a function of the soil pH
are given in Fig. 3.2:5. In general, after each
crop the curves representing shallow and deep
applications shifted to the left indicating a de-
crease of pH values at all lime rates. Thus, the
residual effect of lime diminished with cropping.
Significant differences occurred between shallow
and deep incorporations of lime with the first
three crops in which the differences in pH values
at 15-30 cm soil layers were large. With time,
these differences became smaller and practically









Shallow Incorporation

80 -15 cm Soil Depth
0


60


40


20


0


Deep Incorporation

S0- 15 cm Soil Depth


I I I I I
1 2345


.15-30cm Soil Depth


1 2 3 4 5


CROP SEQUENCE


Figure 3.2:3.


Residual effects of lime rates and depth incor-
poration on the Al saturation after five crops.
Brasilia, 1972-1976.


80 r


60 F


40


20 -










Table 3.2:7.


Seasonal and cumulative gran yields of five crops (4 for
corn and 1 for sorghum*) as affected by shallow and deep
lime applications.


Seasonal Grain Yields
Lime
Depth rates 1 2 3 4 5 Cumu-
of lime applied Rainy Dry Rainy Rainy Rainy lative Maximum
incorp. in 1972 72-73 73 73-74 74-75 75-76 yield yields

cm ton/ha ------------ tons/ha --------------------- -- % --

No Lime 0 2.11 4.57 0.88 1.48 2.36 11.40 41


Shallow 1 3.42 5.28 1.47 3.52 4.28 17.97 64
(0-15)
2 3.53 5.69 1.86 5.58 4.32 20.98 75

4 4.00 5.90 2.27 6.23 4.62 23.02 82

8 3.72 5.96 2.05 6.88 5.41 24.02 85


Deep 1 4.02 5.88 2.09 4.57 4.43 20.99 75
(0-30)
2 4.34 5.68 2.59 5.86 4.60 23.07 82

4 4.80 5.86 3.06 6.42 4.81 24.95 89

8 4.80 6.68 3.60 7.06 5.97 28.11 100

LSD 05 0.57 0.55 0.76 0.64 0.67

CV (%) 26 13 28 10 12


*Sorghum yield is an average of two sorghum varieties.










Shallow Placement (0-15cm)


20 -


I I I I I


2
1973


3
1974


4
1975


5
1976


I
1972


Deep Placement (0-30cm)
(Maximum Yields, tons/ha)
(4.8) (6.7) (3.6) (7.1) (60)
r 6--A -6


I I I I I


192
1972


2
1973


3
1974


4
1975


5
1976


CROP SEQUENCE

Figure 3.2:4. Corn grain yields over time as influenced by various
residual lime rates at two placements. 1972-1976.
Brasilia.


100


80


60


40








Soil Depth 0-15 cm Soil Depth 15-30 cm
D: Deep Placement (0-30cm)
S: Shallow Placement (0-15cm)
100r b S
\ IS


- Is- Crop





2nd Crop
7~ Dr


I I I I I


- 1D

S


3r- Crop


I a il
I-


4t Crop


I 1 a a I


60h1


2I I I
4.5 5.5 6.5


th Cro
5- Crop


I & I I
4.5 5.5 65


SOIL pH


Figure 3.2:5.


Corn grain yields over time as influenced by residual
lime placement and plotted as a function of soil pH.
1972-1976. Brasilia, Brazil.


60 1


,D






r D


100


60


20
100


60


20 -


201
1001


r










disappeared in the fourth and fifth crops. The
main reasons seemed to be a result of the de-
crease in the residual effect of lime incorporated
to a 30 cm depth and the decrease in Al satura-
tion in the shallow lime treatments at the
15-30 cm depth due to a downward movement
of Ca and Mg into this soil depth.
Root Depth and Downward Movement of
Basic Cations
Eighty days after planting, three pits were
dug and opened to 100 cm in plots which
received no lime and 4 tons lime/ha shallow and
deep incorporation, respectively. As expected,
depth and proliferation of roots increased with
increasing depth of liming (Fig. 3.2:6). Where
no lime was applied most of the roots were con-
centrated close to the row and just in the
0-15 cm soil layer. This type of rooting distribu-
tion could be related to the banded P applica-
tion. At 4 tons lime/ha shallow application a
high concentration of roots still were observed
in the 15 cm soil layer but their distribution
covered all this layer, with some of them having
passed 20-30 cm below the level to which lime
had been incorporated. Deep liming resulted in
a fairly uniform rooting distribution in the
0-15 cm soil layer with considerable roots
irregularly distributed to a 50 cm depth. This
differential distribution of roots emphasized
the necessity for a more detailed soil sampling
to deeper layers in order to evaluate the effects
on soil properties of lime rates and depth of
incorporation. After harvest of the fifth corn
crop, soil samples were taken in several layers


to a 90 cm depth. Changes in pH, exchangeable
Al, Ca, Mg and percent Al saturation are shown
in Figs. 3.2:7-3.2:10. The results indicated
clearly that a factor other than simple pH effect
was involved. As lime rates were increased,
notable differences in pH values at least until
45 cm depth were noted. The greatest difference
was found between 0 and 8 tons/ha shallow and
deep incorporation. The data strongly indicate
that after five years substantial Ca and Mg have
moved through the profile to depths of 45
to 50 cm.
Proportional to the lime rate, Ca and Mg con-
centrations increased and Al saturation de-
creased through the profile. Considering 50% Al
saturation as a critical value for adequate corn
growth, the results showed that five years after
shallow applications at the rates of 2 and
4 tons/ha this critical Al saturation value is
found at 30 cm deep. With deep placement
(0-30 cm) of 2 tons/ha the critical value is found
around 35 cm deep and for 4 tons/ha near
45 cm deep. With the highest lime rate
(8 tons/ha) it is interesting to observe that 50%
Al saturation was encountered somewhere be-
tween 50 and 70 cm deep under both shallow
and deep incorporation. In addition, at these
highest rates of lime incorporated at 0-15 and
0-30 cm the neutralization of aluminum in the
sublayers was quite similar. Small differences
were observed with exchangeable Al and Ca +
Mg under both shallow and deep placement at
the highest lime rates. All these results are show-
ing the benefit of movement of basic cations











IMt Ai-


Figure 3.2:6a. Corn root distribution as a function of depth in the
zero lime treatment of the experiment on lime ratesand depth of
incorporation. Concentrated root zones correspond to regions of
banded P applications. Fifth crop. Brasilia, 1976.








LIME EXP
4 TON/HR

VHflHaW]


Figure 3.2:6b. Corn root distribution as a function of depth in the
residual 4 ton/ha lime treatment with shallow (0-15 cm) incor-
poration. Fifth crop after liming. Brasilia, 1976.




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