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Research program on soils of the tropics, annual report for ...

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Title:
Research program on soils of the tropics, annual report for ...
Cover title:
Agronomic-economic research on soils of the tropics
Spine title:
Research on soils of the tropics
Abbreviated Title:
Res. program soils trop., annu. rep.
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North Carolina State University -- Soil Science Dept
Place of Publication:
Raleigh N.C
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The Dept.
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Annual
regular
Language:
English
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1 v. : ill. ; 28 cm.

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Subjects / Keywords:
Soils -- Tropics -- Periodicals ( lcsh )
Soils -- Periodicals -- Latin America ( lcsh )
Agriculture -- Tropics -- Periodicals ( lcsh )
Agriculture -- Periodicals -- Latin America ( lcsh )
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serial ( sobekcm )

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Dates or Sequential Designation:
1976-1977.
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Electronic resources created as part of a prototype UF Institutional Repository and Faculty Papers project by the University of Florida.
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Soil Science Department, North Carolina State University.

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0277-5573 ( ISSN )

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Preceded by:
Tropical soils research program, annual report
Succeeded by:
Agronomic-economic research on soils of the tropics

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.
under
Contract 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 figures. 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 Ill, Coordinator
Tropical Soils Research Program




PERSONNEL
Administration Intercropping Studies
Charles B. McCants, Department Head Robert E. McCollum, Project Leader
Pedro A. Sanchez, Program Coordinator1 Clifton K. Hiebsch, Research Assistant
John J. Nicholaides III, Program Coordinator2 Alvaro Cordero V., Research Assistant
Bertha I. Monar, Administrative Secretary Michael K. Wade, Research Assistant
Dawn M. Silsbee, Bilingual Secretary Cesar E. Lopez, Research Assistant
Cathy L. Langley, Research Technician Lynn F. Dickey, Research Technician Soil Characterization and Classification
Mary Jo Stephenson, Research Technician Stanley W. Buol, Project Leader
W. Couto, Visiting Assistant Professor Amazon Jungle of Peru Jerry M. Bigham, Research Assistant
Dale E. Bandy, Project Leader Richard Schargel, Research Assistant
J. Hugo Villachica, Research Assistant Robert A. Pope, Research Assistant
Jose R. Benites, Research Assistant W. Couto, Visiting Assistant Professor Economic Interpretation
George C. Naderman Jr., Assistant Professor Robert B. Cate Jr., Project Leader
D. Keith Cassel, Associate Professor Arthur J. Coutu, Professor (Economics)
Stanley W. Buol, Professor Michael K. Wade, Research Assistant Extrapolation
Cesar E. Lopez, Research Assistant W. Couto, Project Leader
Stanley W. Buol, Professor 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
1Through 1976.
21977 present.
3Cornell University staff member working on cooperative project.




TABLE OF CONTENTS
Page
1 INTRODUCTION
1.1 H ighlights ............................................... ........ 3
1.2 Collaborating institutions and individuals ............................... 7
2 AMAZON JUNGLE OF PERU
2.1 Crop w eather ..................................................... 12
2.2 Continuous cropping experiments ..................................... 16
2.3 Fallow w ith 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 w eather ..................................................... 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 N itrogen 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 (Conytinued)
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




1
INTRODUCTION
From the time the small farmer prepares his soil for planting, he is as interested in and affected by the economic return on his investment as he is the agronomic yield he will realize.







3
This is the sixth annual report of the Soil with similar fertility limitations and thus Science Department's Research Program on bridges the gap between the subdisciplines of
Soils of the Tropics and covers the period from soil survey and soil fertility; 3) the data are 1976 through early 1977. Hence, this report economically interpreted to evaluate the prodeparts from precedent in that it will be called fitability of the proposed soil-crop manageAnnual Report for 1976-1977. The bulk of the ment systems and also to provide physical co1977 data will be included in the forthcoming efficients for economic planning means such as report, Annual Report for 1977-1978. linear programming and sector analysis. The
This research program has been supported by format for this report follows that established the U. S. Agency for International Develop- by the 1975 Annual Report in that the staff rement under Contract AID/ta-C-1236 which sponsible for each research project are identiruns for a three-year period from July 1, 1975 fied to give more direct credit to the individthrough June 30, 1978. uals involved.
The overall objectives of the program have
been focused into developing economically- HIGHLIGHTS
sound soil-crop management systems for Amazon Jungle
1) acid tropical savannas and 2) acid tropical A new fertilization strategy in the continrainforests. The field research activities, to uous cropping experiment successfully reversed achieve these objectives, continue to be based the severe crop yield decline which had ocin Brasilia, Brazil for the savannas and in Yuri- curred in 1975. The main causes of the decline maguas, Peru for the jungle areas. were fertility-related. When the lime, N, P and
The final objective of the contract is to K rates were increased along with inclusion of
gather additional information needed for estab- Mg, B, Cu and Mo fertilizers, yields of rice, lishing a sound basis for extrapolating the re- corn, soybeans and peanuts increased marksearch results to other tropical areas of the edly. Inference drawn from these findings is world with similar soil management situations. that abandoned or soon-to-be-abandoned The three supporting activities to achieve this chacras can be recovered and farmed continobjective are as follows: 1) Soil characteriza- uously and economically. tion studies are used with basic laboratory and For example, using a rice/corn/soybean rotagreenhouse studies to determine the soil prop- tion and no fertilizer or lime, a farmer in the erties of little-known tropical areas in order to Yurimaguas area would realize a new profit of better comprehend certain basic concepts not $128/ha/yr on a plot of land that he would fully understood at present; 2) the soil fertility normally abandon after two croppings. Uticapability classification system (FCC) is uti- lizing the 1974-1975 fertilizer strategy of lized as a practical means for grouping soils 1000-240-79-240 kg/ha/hr of lime-N-P-K, the




4
farmer could realize a net profit of $579/ha/yr micronutrient shotgun spray of Cu, Fe, Mn and on the same parcel of land. Employing the Zn sulfates and B, Mo, lime increased corn
same rotation on the same land area with the yields from 1.2 to 5.2 tons/ha. Soybean yields improved 1976-1977 fertilization strategy of were increased lessdramatically by this spray. 1000-350-211-333 kg/ha/yr of lime N-P-K, the Each of the micronutrients were then evalfarmer could obtain a new profit of $1539/ uated in several crops. In a newly cleared and ha/yr. This $1539/ha/yr net profit represents burned chacra, soybean yields were increased a 1202% increase over no fertilizer or lime and from 1.5 to 2.1 tons/ha with the 2 kg Cu/ha a 266% increase over the lower fertilizer rates and from 2.1 to 2.6 tons/ha with 0.5 kg B/ha. of 1974 and 1975. Soybean yields decreased to 2.1 tons/ha when
Viewed another way, the $ profit/$ invested B rates exceeded 0.5 kg/ha. Soybeans did not in fertilizer and lime was $2.66 for the 1976- respond to Mo, Mn or Zn. Also on newly 1977 strategy and $1.72 for the 1974-1975 cleared and burned land, peanut yields were instrategy. creased from 3.0 to 4.5 tons/ha with applicaUtilizing the 1976-1977 fertilization strat- tion of 0.5 kg B/ha and from 3.8 to 4.5 tons/ha egy, soybean and peanut yields increased to 2.5 with 1.5 g Mo/kg seed. and 4.5 tons/ha, respectively, while rice and When chacras are continuously cropped, one corn yields approached 3.5 and 4.0 tons/ha, would expect response to B, Mo and Cu applirespectively. cations. No soybean or peanut response to Zn
As was noted in the 1975 Annual Report, or Mn was obtained. However, the question realthough the response to lime is great, the mains as to how this response or lack of reresidual effect of Ca(OH)2 is rather short-lived. sponse to micronutrients will change as plants For instance, 1 ton Ca(OH)2/ha had a residual utilize the native micronutrients in the soil. effect of only 10 months. Corn yield response Present data indicate the need to apply 0.5 and to Ca(OH)2 applied 10 months earlier was 1.0 kg/ha of B and Cu, respectively per crop of
linear with yields increasing from 0 to 5.2 soybeans and peanuts and 1.5 g Mo/kg peanut tons/ha as lime increased from 0-4 tons/ha. The seed. suggested application rates of 3-4 tons/ha/3-4 An additional research emphasis was begun years appear agronomically feasible. By reduc- to look at integrated cropping systems using ing Al saturation in the soil from 48 to 24%, lower inputs and relay cropping. Preliminary rice yields were increased to 3.5 tons/ha. results have indicated no substantial negative
Preliminary research found that Mg and sev- effect of the lower fertilizer and lime rates on eral micronutrients became limiting after a yields of relay-cropped rice, cowpeas, soynewly-cleared field had been twice cropped. A beans, peanuts, cassava and sugarcane.




5
A six-year kudzu fallow study was initiated slightly inferior. Chemical soil analysis and to determine whether it is possible to shorten depth of rooting measurements indicated that the traditional 20-year fallow period of the downward movement of Ca and Mg in the deep slash-and-burn system for recycling of nutrients and shallow lime incorporation treatments has to regenerate an exhausted soil. Should it be diminished the differences in subsoil acidity possible to reduce the fallow period to 4 years, between incorporation methods and the ina small farmer could permanently farm 5 hect- creased rooting depth has improved water reares by rotating a 1-ha cropping area/yr with serves for plants during dry spells. A corn expe4 hectares in different stages of fallow. riment with roots extending to a 120 cm depth
The evaluation of adaptation of corn vari- yielded 6 tons of grain/ha despite a 40-day dry eties to the Yurimaguas environment found spell of which 19 days occurred after 50%
that the relatively short, lodging resistant and tasseling. early maturing Amarillo Planta Baja outyielded After six consecutive corn crops, two strateall other varieties tested under both adequate gies for obtaining desirable soil P levels were and low lime and fertilizer levels. Corn grain evidenced. An initial broadcast application of yields of this variety at the two fertility condi- 141 kg P/ha with maintenance applications of tions were 3.86 and 2.09 tons/ha, respectively. 35 kg P/ha before each crop provided yields Yields of all 10 varieties planted in September which were 80% of the treatment receiving an exceeded those planted in April by 43%, due initial broadcast application of 560 kg P/ha. A primarily to improved rainfall distribution cumulative yield of 72% of the maximum was during the latter growing season. obtained with an application of 35 kg P/ha
The establishment of a meteorological sta- broadcast and 35 kg P/ha banded before each tion at the Yurimaguas Experiment Station has crop. Yearly differences in input/output cost allowed for the first detailed views of the cli- may dictate a given strategy. Based on October, matic pattern of the area. These detailed data 1976 prices it was economically feasible to will allow for improved interpretation of the apply as much as 440 kg P/ha. agronomic research results. The satellite experiment on the loamy Red
Savannas Yellow Latosol continued to stress the imporThe long-term experiments on the residual tance of fully understanding the factors limiteffects of liming and fertilizer applications on ing the utilization of Cerrado Oxisols. The high Oxisols of the Cerrado of Brazil continued for available water content, lower P fixation and the fourth year. The original application of decreasing Al saturation with depth in this soil 8 tons lime/ha incorporated deep (0-30 cm) resulted in sustained high yields with lower
continued to provide the maximum corn yield inputs of lime and P fertilizer. although shallow incorporation was only




6
A new experiment was installed to evaluate applications should have significant effects on response to K and Mg. Of special interest is the the ion retention properties of these Oxisols. application of 62 kg K/ha which almost Large texture variations were observed
doubled corn grain yields providing a return among 44 representative surface samples of equivalent to 9.3 times the cost of the K fer- Cerrado soils. The chemical composition, ion tilizer. exchange and P sorption characteristics of
For the fourth consecutive year corn grain these samples varied according to surface texproduction was near 4 tons/ha in the absence ture. Water release characteristics resembled of applied N. Maximum yields were obtained those of sand irrespective of soil texture.
with the application of 200 kg N/ha, but 82% Intercropping of the maximum was produced with 80 kg Field experiments in North Carolina have
N/ha. compared the N response and productivity of
Studies on varietal tolerance to Al toxicity several intercropping combinations relative to and low available P were continued in both monocultures of the same crops. Land equivgreenhouse and field experiments. Among the alency ratios indicated that productivity was species and varieties studied the most tolerant increased when corn competed interspecifically cultivars to P and Al stress were Taylor Evans with soybeans or snapbeans. The proper selecY-101, Pratgo Precoce, Agroceres-259 and tion of intercropping combinations was exemCarioca-1030 for sorghum, rice, corn and plified by the apparent nutritional incompatibeans, respectively. These studies indicate that bility between intercropped corn and sweet the most satisfactory method of crop manage- potatoes. ment on savanna Oxisols involves this use of Considerations on some of the methods curvarieties tolerant to high Al saturation and low rently used in intercropping studies have reavailable P combined with low levels of surface vealed that time is an important factor in comapplied lime. parisons of crops in mixture and monoculture.
Additional information on the properties of The area-time equivalency ratio (ATER) is proCerrado soils were obtained by on-campus posed as a feasible method of accounting for
studies. Investigations on P sorption indicated time in such comparisons. that previous P applications were more effec- Extrapolation tive than liming materials in reducing addi- The mineralogy of iron compounds in chemtional P sorption, but the liming effects were ically similar pairs of red and yellow colored sufficient to cause overestimations in soil P re- soils indicated hematite and goethite were the quirements for field conditions when P sorp- major iron components in the clay sized fraction measurements were performed on unlimed tions. Redness of the soils was associated with
soils. The increases in net negative soil charge increasing amounts of hematite relative to through the combined effects of P and lime goethite.




7
The "i" modifier in the FCC system, which institutions and involves a high degree of characterizes soils fixing considerable P by iron collaboration. compounds was evaluated over a broad range In the Amazon Jungle of Peru, field research
of Oxisols, Ultisols and Alfisols. Results sug- is conducted at the Yurimaguas Experiment gested that a useful criterion is both a ratio of Station which is part of the Centro Regional de iron oxides to percent clay greater than 0.15 Investigaciones Agropecuarias III ( CRIA III) and more than 35% clay in the plow layer. of the Ministerio de Alimentaci6n. Supporting
Assessment of the FCC system was per- laboratory work is conducted at the La Molina
formed using soybean experiments from 184 Experiment Station. The Direcci6n General de
sites in southeastern United States. High yields Investigaciones of the Ministerio de Alimentawere obtained on a variety of soil conditions ci6n has assigned Dr. Carlos Valverde as project using the appropriate management. Although leader, representing Peru. Dr. Valverde has the required management depended largely on been very effective in expediting administrative soil properties the influence of these properties matters with the Peruvian Government. The on yield varied between years. International Potato Center (CIP) plays a major
Characterization studies were continued in role in providing administrative and logistical the savanna and rainforest regions of Vene- support. In turn, the program grows its potato zuela. Soils from southern Venezuela were trials at Yurimaguas as the lowland tropical more intensively weathered and had lower station for adapting potatoes to the region. The
effective CECs than soils of the northern Peruvian meterological network, SENAMHI,
region. The Ultisols and Alfisols were con- established a meteological station at Yurimasidered intergrades to Oxisols when this cri- guas in 1976, which has allowed for the first terion was applicable, detailed looks at the climatic pattern of this
Initial economic analysis of data produced area.
by the Yurimaguas program has focused on de- In the Cerrado of Brazil, this project is confining factors necessary to produce near max- ducted jointly with Cornell University and the imum yields. Various alternatives for producing Empresa Brasileira de Pesquisa Agropecuaria the different crops have been quantified. (EMBRAPA) at the Centro de Pesquisa AgroResults from this phase of the analysis have de- pecuaria dos Cerrados, located about 40 km lineated specific areas where additional agro- north of Brasilia. The USAID Mission in nomic research is necessary. Brasilia and the Interamerican Institute of Agricultural Sciences provided valuable logistical
COLLABORATING INSTITUTIONS AND support. EMBRAPA has assigned Mr. Edson
INDIVIDUALS Lobato as project leader, representing Brazil.
The research reported is conducted in coop- Cornell and N. C. State staff stationed at the eration with several national and international Cerrado Center form an integral part of the Center's research staff.




8
Several extrapolation studies are also col- Jos6 del Carmen Muro, Director de Investigalaborative in nature. Soil characterization stud- ciones, Ministerio de Agricultura, DGIA, ies have been conducted with partial financial Lima. support in the form of scholarships for grad- Ruben Mesia P., Head, Yurimaguas Experiment uate students from the USAID Mission to Station.
Colombia, the Ministerio de Obras Publicas of Mario Cano, Soils Department, La Molina Venezuela, The Fundo de Amparo a Pesquisa Experiment Station.
do Estado de Sgo Paulo, Brazil. Data for eval- Humberto Mendoza, Plant Breeder, Internauating the Fertility-Capability Soil Classifica- tional Potato Center. tion System has been provided by EMBRAPA, Richard L. Sawyer, Director General, Internathe Instituto Colombiano Agropecuario, Insti- tional Potato Center. tuto Geogrifico Agustin Codazzi in Colombia. Carlos Bohl P., Executive Director, InternaThe extrapolation work at Pucallpa, Peru is in tional Potato Center. cooperation with the Instituto Veterinario de William Hamann, Assistant Executive Director, Investigaciones Tropicales y de Altura (IV ITA). International Potato Center. Dr. Jos6 Toledo, as the individual in charge of Oscar Gil, Controller, International Potato the Tropical Pasture Production and Evaluation Center. Research Line, is directing all extrapolation- Veronica de Franciosi, Assistant to Executive related activities at Pucallpa. Officer, International Potato Center.
The following individuals from the dif- Leonard Yaeger, Director, USAID/Peru
ferent cooperating institutions provided sub- Ricardo Villalobos, Deputy Director, USAID/ stantial administrative support or are coauthors Peru of some of the research projects. We wish to John O'Donnell, Agricultural Officer, USAID/ acknowledge and recognize their assistance at Peru.
this time. Milton Lau, former Food and Agriculture
PERU Officer, USA ID/Peru.
Mariano Segura B., Director General de Investi- Rollo Ehrich, former Deputy Food and Agrigaciones Agrarias, Lima. culture Officer, USAID/Peru.
Carlos Valverde S., Project Coordinator for the BRAZIL
Ministry of Food and Director of the Jos6 Ireneu Cabral, President of EMBRAPA
Centro Regional de Investigaciones I-La Almiro Blumenschein, Director of EMBRAPA Molina. Elemar Wagner, Director, CPAC, EIMBRAPA
Manuel LIavera, Director del Centro Regional Wenceslau G. Goedert, Associate Director,
de Investigaciones Agrarias II I-Tarapoto. CPAC, EMBRAPA.




9
Edson Lobato, EMBRAPA Project Coordinator Robert B. Musgrave, Professor of Agronomy,
Gilberto Paez, Head of the Data Processing Cornell University.
Department, EMBRAPA. Elcios Martins, Research Technician, CornellWilson V. Soares, former Associate Director, NCSU Project.
Cerrado Center. Clibas Vieira, Professor, Universidade de
Jose M. Barcellos, former Head of the Brasilia Vicosa.
Experiment Station. Robert Schaffert, Brazilian National Sorghum
Frank Campbell, Chief, USAID Affairs Office- Program.
Brazil. Ady Raul da Silva, Brazilian National Wheat
William Rodgers, former Agriculture and Rural Program-CPAC.
Development Officer, USAID/Brazil. Knut Mikaelson, Centro de Energia Nuclear na
William Gelabert, former Acting Director, Agricultura.
USAID/Brazil. COLOMBIA
John Young, USAID/Brazil. Servio T. Benavides, Instituto Geografico
Matthew Drosdoff, Professor of Tropical Soils, Agustin Codazzi, Bogota.
Cornell University. Luis Alfredo Leon, Instituto Colombiano AgroDavid R. Bouldin, Professor of Soil Science, pecuario, Palmira.
Cornell University. James M. Spain, Soil Scientist, CIAT, Palmira.







11
AMAZON JUNGLE OF PERU
Arial view of Yurimauas Aricultural Exeriment Station.
Aerial view of Yurimaguas Agricultural Experiment Station.




12
Research at the Yurimaguas Experiment Sta- soil to be deep, well drained, quite acid, low in tion in the Amazon Jungle of Peru in 1976-1977 organic matter, and deficient in N, P, K, Ca, Mg continued to gather information for developing and, in some cases, S, B, and Mo. As earlier reagronomically and economically sound soil man- ported also, the sandy topsoil texture contriagement practices for continuous cultivation in butes to the susceptibility of this Ultisol to soil jungle areas where population pressures dictate compaction and at the same time, prevents any an alternative to shifting cultivation. The expe- serious phosphorus fixation problems. rimental strategy followed continued to be that
of 1) determining the factors responsible for the 2.1 CROP WEATHER marked decline in crop yields following clearing, D. E. Bandy typical of shifting cultivation in acid soils, and In 1976 a meteorological station was estab2) the development of corrective measures to en- lished at the Yurimaguas Experiment Station in able continuous cultivation in small farming cooperation with SENAMHI, the Peruvian meteunits with emphasis on low energy technology orological network, which has its area headoptions. quarters in Tarapoto. Most of the results presenThe research has dictated higher fertilization ted in this report were taken at the Experiment levels in the central experiment of continuous Station. Other results were provided by the cropping, which now also includes micronu- Yurimaguas Airport, which is 6 km from the
trients. The phosphorus and potassium studies, station. as designed in earlier experiments, have contin- For the first time, the detailed climatic patued. New experiments in 1976 and 1977 at the tern for the Experiment Station can be observed
Yurimaguas Experiment Station included (Table 2.1:1). The greatest surprise is perhaps
1) corn varietal response to various agronomic that it is not as hot as one might expect, alpractices, 2) lime, K, Mg and micronutrient though this does not mean that one does not
studies with rice, corn, peanuts and soybeans, feel uncomfortable living there due to the high 3) substituting kudzu fallow for forest regenera- relative humidity and low amounts of wind. tion, and 4) integrating cropping systems. With In terms of plant growth, the temperatures the new meteorological station established at the are not too high during the day (absolute max. Yurimaguas Experiment Station, the detailed cli- 35.80C or 960F) or night (avg. 22.50C or 710F) matic pattern for this area was observed for the to adversely affect plant growth or yield. On the first time. contrary, the temperatures are quite favorable
As in the previous years, all experiments were for such crops as maize, sugar cane, rice, cassava, conducted on the Yurimaguas soil series Ultisol, peanuts, and soybeans. A max-min temperature classified as Typic Paleudult, fine loamy, sili- reading system does not show the duration of ceous, isohyperthermic, which is considered to any temperature reading; thus, it is possible that be representative of the region. Soil analyses re- night temperatures are too high for most of the ported in the previous annual reports show the night, falling very rapidly just prior to daybreak.




Table 2.1:1. Climatic data for the experimental station at Yurimaquas, Peru, 1976.
TEMPERATURE, C
RELATIVE SOLAR
MONTH Maximum Minimum Average PRECIPITATION WIND HUMIDITY RADIATION
(mm) (m/sec) (%) (Cal/cm2/day)
January 30.8 22.0 26.4 396 0.86 84.8 337
February 31.5 22.2 26.9 67 1.14 80.5 357
March 31.0 22.3 26.7 222 0.92 82.5 355
April 30.5 21.9 26.2 245 0.53 89.7 332
May 30.6 22.5 26.6 167 0.53 87.4 340
June 30.6 21.9 26.3 93 0.42 86.5 320
July 30.1 17.9 24.0 62 0.67 76.8 371
August 31.2 19.9 25.6 126 0.55 77.1 407
September 32.6 19.6 26.1 129 0.55 77.5 416
October 32.1 21.1 26.6 402 0.61 81.2 397
November 31.7 21.1 26.4 230 1.17 81.1 408
December 31.1 21.2 26.2 219 0.88 82.6 387
Year 31.2 21.1 26.2 2359 0.74 82.3 369
Absolute 35.8 11.2 115 609
Daily
Reading Sept. 17 July 23 Oct. 20 Oct. 23
(Date)




14
If this is the case, high rates of dark respiration these are deep, well drained soils, such high could be occurring. This, rather than photores- amounts and frequencies of rainfall make it expiration as was previously thought, may account tremely difficult for a farmer to plant and harfor some of the low yields of previous crops, vest his crops and to control weeds, diseases, and since daytime temperatures are not that high. insects. Crop growth and yields are also negaIn addition, Table 2.1:1 shows that solar tively affected by low solar radiation and proradiation is not high enough to cause significant longed periods of water saturated soils. photorespiration losses. On the contrary, low Conversely, plant water deficit may also resolar radiation could be an important factor in duce yields even in the humid environment of limiting yield potential during the rainy season. Yurimaguas due to poor rainfall distribution.
Wind speeds do not seem to be too high, but The 21-year rainfall records for the Yurimaguas a seasonal effect is noted. The rainy season area show an average of 100 mm during the
shows more windiness than the cooler, drier driest months of June, July, and August (Annual
months. However, the monthly data results may Reports 1974, 1975), but this can be extremely be misleading, since strong gusts of wind appear misleading. For example, Fig. 2.1:1 shows that in the drier season for short periods of time, most cf the rain falls during one thunderstorm. usually before a storm. These strong wind gusts Of the 93 mm of rain that fell in June 1976, can cause serious yield reductions of some crops 57.3 mm fell in one 24-hour period, and 78% of due to plant lodging, the monthly total fell during the same 3-day
Yurimaguas is similar to many other places rainy period.
in the tropics in that rainfall distribution may be July was even worse than June. Severe water a serious problem even though the yearly or stress was observed on all crops. Benites; and
monthly results show sufficient rainfall to grow Naderman have shown (Sec. 2.4) that water most crops the year around (Table 2. 1: 1). stress was probably one of the main factors conIf one studies the rainfall data shown in the tributing to lower corn yields in the April plantAnnual Reports of 1974 and 1975, it can be ing compared to the September planting.
seen by the large 20% variability curves that In conclusion, it can be stated that the climonthly rainfall distribution, especially during mate at Yurimaguas and in other humid tropical the rainy season, varies greatly. The large varia- areas of the Amazon jungle basin, is, in general, tion in rainfall is not serious in terms of causing quite favorable to crop production. However, plant water stress during the rainy season, but the climate can also cause serious yield reducexcessive rainfall can be a problem. For ex- tions if proper agronomic practices are not folample, the daily rainfall distribution for January lowed. The climate strongly mandates the pest 1976 is shown in Fig. 2.1:1, where about control program required at Yurimaguas. For
400 mm of precipitation was recorded. It rained example, fungus diseases start becoming a seri19 days out of 31 days in January. Even though ous problem about three months into the rainy




15
60 January, 1976
40
20
0f 0 .
E
E60 June, 1976
- 60
Z
S40
40I
20
S10 12 4 16 18 20 22 24 26 28 30 DAY 0S
Figure 2.1:1. Rainfall distribution for January, June and July
60 Ju1976 at Yurimauas Peru.
40
20
' .......... I!
0 2.........o01214 1612224"26 28"3 DAYS
Figure 2.1:1. Rainfall distribution for January, June and July
1976, at Yuriniaguas, Peru.




16
season and prohibit the planting of cowpea and and economically sound in 1974, were found to some soybean varieties. Toward the end of the be inadequate in 1975 (Annual Report 1975). rainy season and the start of the drier season Minor changes made in these fertilizer strategies (April through July) insects and birds become during 1975, i.e., raising the amount of N apthe major pest problem. Weed control is also plied to the soil from 80 to 100 kg/ha, did not closely related to the climatic pattern. At least significantly improve yields. These minor four cultivations are needed for adequate weed changes were reported in the 1975 Annual control in crops grown during the rainy season, Report. whereas one, or at most two, weedings are With these results, it was obvious that a
needed during the drier part of the year. change in the research strategy for continuous
cropping was needed. We were studying mod2.2 CONTINUOUS CROPPING EXPERIMENTS erate to low fertilizer rates, even dropping some
J. H. Villachica and P. A. Sanchez of them, to lower the costs. However, yields obAccording to the plan of work outlined for tained during 1975 were also moderate to low. 1976, rice was planted in early February 1976 in By March 1976, the decision was made to crop sequence 1 (continuous upland rice) and change our fertilization strategy to levels that crop sequence 3 (rice--corn-soybean) in all would ensure better yields. Satellite experiments three chacras. The only exception was contin- with S, Mg, K, lime and micro-elements were uous rice in Chacra 3, which was planted by very helpful for establishing these new levels. December 1975. The treatments and the level of The missing nutrient strategy was changed to nutrients applied were the same as those de- one of having a complete as a treatment and scribed in the 1975 Annual Report. By the mid- then adding other elements to form the addidle of March 1976, some results on soil and tional treatments (Table 2.2:1). Since continplant analyses were obtained. Results on the sat- uous upland rice had already achieved the goals ellite experiments with lime, K, Mg, and micro- for which it was designed, it was changed for a nutrients were also available. All this data aided crop sequence with better agronomic and ecoa better understanding of what occurred in the nomic possibilities. Thus, rice-soybean-peanut plots of continuous crops during the last 6-8 was begun in the plots formerly used for continmonths of 1975. uous rice. In March 1976, rice was growing very
It was evident that new fertility levels had to poorly in all chacras and crop sequences, so it be developed for continuous cropping in all the was harvested and straw dry matter production chacras. The results of three years of research in measured. At that time, it was too late in the continuous cropping in Yurimaguas were show- season to plant rice again, so the next crop in ing that the model that we had been using was each sequence (soybeans in new sequence 1, good only for no more than two years and that corn in sequence 3) was sown. The results obour fertilization strategies, which were adequate 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
I 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.




18
Changes in treatments and the amounts of The rice-guinea grass system was continued
fertilizer and amendments applied are presented as described in the 1975 Annual Report. Thus, a in Table 2.2:1. The non-tilled check was main- six-week interval cut was given to each plot, and tained, and the tilled check was fertilized and 320-50-320 kg/ha/year of NPK were applied to mulched (treatment 2). The complete fertilizer the complete plot. The N and K were split in level was higher than the previous complete and equal amounts after each cut, while P was apalso included Mg, Zn, Cu, B, and Mo, at opti- plied once a year. Maintenance treatment conmum rates as determined by the 1975 results. tinued receiving 120-20-90 kg/ha of NPK. FerSince soil analysis results cannot be obtained as tilization strategies for all other treatments conrapidly as desirable, there is a time lag for cor- tinued as before. recting soil fertility changes. For this reason, a Rice-Soybean-Peanuts Sequence high complete treatment was designed to be As previously mentioned, rice growth during
used (treatment 7). Should there be a deficiency early 1976 followed the same pattern described of any element being applied, this treatment for 1975 (1975 Annual Report). Thus, it was should so indicate, giving higher yields than the not doing very well. For this reason, and for complete. time considerations, it was harvested at 60 days
Lime and kudzu were incorporated to of planting. After rice was cut, in April 1976,
10-12 cm depth when applied. Lime, as soybeans (cv. National) were planted in the same
Ca(OH)2, was applied 10-15 days before plant- plots, but using the new treatments. ing. Kudzu was incorporated the day before The results of soybean grain yield in Chacras
planting. Mulch was applied the day following 1, 2, and 3, obtained during 1976, are presented planting. All the fertilizer P, K, Mg, Zn, Cu, and in Table 2.2:2. Yields of soybeans ranged from B were broadcast at planting time and mixed 0.3 to 2.5 tons/ha. Highest yield was 2,725 with the soil and the kudzu. Nitrogen applica- kg/ha (41 bu/acre), excellent even by North tions were equally split at 18 days and 45 days Carolina standards. When the former mainafter planting. When SCU was used, it was ap- tenance plots received lime, incorporated kudzu, plied at planting time. Molybdenum was applied and guinea grass mulch, soybean yields increased as a coating to the seeds. The fertilizer sources to about 1,500 kg/ha (treatment 4). When lime used were urea (or SCU in treatment 6), simple and all the nutrients were added, with and withsuperphosphate, potassium chloride, magnesium out kudzu incorporated or guinea grass mulch, sulfate, zinc sulfate, copper sulfate, borax, and soybean yields were between 2,000 to 2,500 ammonium molybdate. A foliar application of a kg/ha (tmts. 3, 5 and 6). The yield of the high commercial formulation of micronutrients was complete treatment (number 7) was about equal made at 15 and 50 days after planting for soy- to that of the complete (treatment 5). This indibeans and 15 and 40 days after planting corn. cated that the levels of fertilizers used with the complete were sufficient.




19
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.
1/
Treatment- Soybean grain yield (kg/ha)
No. Identification Chacra 1 Chacra 2 Chacra 3 Average
I Chec!, 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.5 for treatments 241
LSD 05 for treatment x chacra 417
-/Treatments as defined in Table 2.2:1




20
It is worth mentioning that the yield differ- Preliminary evaluation of the data indicate that ences usually observed during 1974 and 1975 the complete plots have yields between 4,000 to
among Chacras 1, 2, and 3 were no longer pre- 6,000 kg/ha. These results also indicate that sent with soybeans in cropping sequence 1 and good yields are still being obtained with the new with corn in cropping sequence 3 (to be shown complete treatments. later). This means that the differences in soil fer- A preliminary economic evaluation of the tility between the complete treatment in all cost of the new fertilizers and their profitability
three chacras, so clearly present during the past is presented at the end of this Section 2.2. years, were overcome by the application of mod- R ice-Corn-Soybean Sequence erately high rates of lime and fertilizers, with Results on corn yield planted in April 1976
very good yield responses. The main implica- are presented in Table 2.2:3. Results of rice dry
tions of this result are twofold. Firstly, yields matter harvested before corn was planted are will be higher regardless of the age or use of the not presented here. Table 2.2:3 shows that yield chacra. Secondly, it suggests that all abandoned of the check treatment was 0.4 tons/ha; when or to-be-abandoned chacras with similar soils can the former maintenance plots were limed and be recovered using this new fertilizer strategy, kudzu and guinea grass mulch were applied, with a high probability of obtaining very good yields improved somewhat but were still low yields. Soybean yields in Chacras 1 and 2 as (treatment 4). When the new complete treatcompared with rice yields in the same plots are ment (number 5) was used, yields increased shown in Fig. 2.2:1. Yield patterns on Chacra 3 sharply up to 3.6 tons/ha. These yields are conare not shown, but they are similar to those of sidered very good for the zone and for the growChacras 1 and 2. It can be observed that the de- ing period-1 10 days from planting to harvesting creasing slope of the response curves has been re- time. Statistical analysis shows that the response versed. Soybean yields with the new complete to the treatments was different between chacras, treatment in Chacra 1 were higher than any of except in treatment 7. The lower yield in the last four crops of rice with the former com- treatment 3 in Chacra 3 was due to a high perplete, even though soybeans do not have as high centage of lodged plants. In general, yields were grain yield potential as rice. Yields were also expected to be higher, but heavy winds at the higher than those obtained with soybean crop- grain filling period produced a high number of ping sequence 3, rice-corn-soybeans, in the lodging plants which, it is believed, reduced the
same chacras during 1975 (1975 Annual Re- yields. When these yields are compared to those
port). All these data indicate the successful rec- obtained in previous years, some interesting data lamations of these plots, are obtained. The decreasing trends in yields in
Peanuts, the next crop in the sequence, were all three chacras were reversed in 1976 (Fig. harvested at the moment of writing this report. 2.2:2). From Table 2.2:3 one also notes that




21
Chacra I
4
3
2
_ %
5" Oct. Apr Oct. Apr. Sep. Mar. Sep. Feb.Apr.
72 73 73 74 74 75 75 76 76 L I R ICE SOYBEAN
CIC
Chacra 2 RICE
4 o Check
o- Complete
a % % Maintenance
Z 3< SOYBEAN
- \J oCheck
2- Complete
- 1a Lime + Kudzu + Mulch
o- --o- --o..
0 I I I I I I
Oct. Apr. Sep. Feb. Aug. Feb.Apr.
73 74 74 75 75 76 76 I 2 3 4 5 6 7
I RICE ISOYBEAN
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 replications. Yurimaguas, 1972-1976.




22
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 replications.
Treatmentl/ 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
LSD5 for chacras 566
. 05
LSD5 for treatment 376
. 05
LSD.5 for treatment by chacra 651
1/Treatments as defined in Table 2.2:1




23
Chacra 1
4
4 o Check
* Complete
3- a Maintenance
(Lime+ Kudzu+
2J- Mulch in
April,'76
0
0 %0\
Oct. Apr. Jun. Nov. Apr. Aug. Nov. Apr. Aug. Apr. C) 1972 --1973-1 1--1974--1 H9754 1976
S R C S S C S R C S C
-j
w
Chacro 2 Chacra 5
z
< 4
o1
3
II
1 1
Oct. Apr. Aug. Nov. Apr. Au. Apr. Oct. Feb. Au Apr.
1973 11974-4 1-1975-1 11976 1974 1-1975- 1976
R C S R CS RC 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.




24
1976 corn yields for the complete fertilization evaluation of the data indicate that soybean plots were higher than those obtained with corn yields were very low in the check plots, as was from 1972 to 1975. expected. Soybean yields over 2,600 kg/ha were
Table 2.2:3 shows that best yields were ob- observed with the complete treatments. These tained with treatment 6, which had the same results will be discussed in the next annual levels of fertilization and soil amendments as report. treatment 3, except that sulfur-coated urea Rice-Guinea Grass Sequences (SCU) was used as the N source instead of com- Results of the total amount of guinea grass
mon urea. Average difference in yield was 501 dry matter produced during seven consecutive kg/ha (14.5% more than treatment 3), indicating cuts in all three chacras are given in Table 2.2:5. the possibility that better N management could In general, yields were low, producing around still improve yields. As previously mentioned, 12 tons dry matter/7 cuts/ha in the complete common urea was split into two applications for treatments in all three chacras. Differences withcorn, while N as SCU was applied only once. in the treatments were observed. The complete Some N leaching loss can still be expected on and the complete with residual P yielded an this sandy soil under the high rainfall conditions average of over 12 tons dry matter/ha/year, of Yurimaguas. which was twice the amount produced by the
The complete plus mulch treatment and the checks and the complete, residual K. However, high complete (treatments 2 and 7) did not yield this "high yield" was not comparable to those as well as the other treatments, even though obtained during 1973 for Chacra 1 (18 tons/ha) they were around the 3.0 t/ha yield level. The and Chacra 2 (20 tons/ha). As was pointed out failure of the high complete treatment to give in the 1975 Annual Report, these low yields higher yields than the complete most likely indi- were, in part, due to changing the cutting frecates that the complete treatment contained suf- quency from 8 to 6 weeks, which was recomficient nutrients. mended by pasture specialists. Table 2.2:6
Table 2.2:4 shows some of the chemical shows that soil exchangeable Ca and available P
properties on these plots sampled in December in the complete treatment in Chacras 1 and 3 1975. Main differences in chemical properties were about adequate and Al toxicity was not a among plots were due to pH and extractable Ca problem in October 1975. However, according and Al. These differences were corrected by in- to the critical levels established at La Molina, the dividually liming each plot, according to its ex- amount of available K was low in Chacra 3 changeable Al. There were also differences in the and medium in Chacra 1. It is also probable that levels of available P and K, but all plots were low by October 1976 (a year after the sample was in these nutrients, regardless of length of crop- taken), the amount of organic matter present in ping of the chacra. Chacra 3 was lower and N availability was reSoybeans following corn were harvested at duced. Soil samples are being analyzed to test the moment of writing this report. Preliminary the hypothesis that N, Mg and K were also limiting 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 H2SO4 Exchangeable
Treatment" pH Olsen P K K Ca Mg Al Al Sat.
No. Identification Cl C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3 Cl C2 C3
---ppm-- ---ppm ------------------------me/lOOg -------------------- --- % -- -1 Check 4.2 4.1 4.5 -- 1 3 25 39 50 .13 .15 .15 .65 1.90 2.50 .4 .6 .7 2.70 2.20 1.75 70 45 34
2 Complete plus mulch 4.3 4.2 4.4 -- 1 3 28 39 44 .13 .13 .14 .70 1.40 1.80 .4 .5 .8 2.70 2.30 1.70 69 53 38
3 Complete plus kudzu 5.3 4.9 4.9 -- 2 7 57 104 75 .19 .28 .18 4.95 5.00 3.95 .6 .5 .8 .40 .40 .90 7 6 15 oI
and mulch
4 Lime, kudzu and 4.4 4.1 4.1 -- 5 6 44 76 55 .16 .24 .15 1.40 2.40 2.80 .4 .5 .8 2.60 2.10 1.50 57 40 29
mulch
5 Complete 5.0 4.4 4.7 -- 6 9 52 81 69 .17 .28 .15 4.05 4.30 3.60 .5 .5 .8 .60 .90 1.00 11 15 18
6 Complete plus kudzu, 5.2 4.6 5.0 -- 4 11 35 33 42 .14 .14 .13 4.80 5.00 4.35 .5 .5 .8 .65 .60 1.00 11 10 16
mulch and SCU as N
source
7 High Complete 4.7 4.4 4.7 -- 4 6 38 60 51 .14 .20 .15 3.10 3.10 3.05 .4 .6 .8 1.40 .90 2.05 27 18 34
"/Treatments as defined in Table 2.2:1




26
Table 2.2:5. Annual dry matter production of Panicum maximum in the rice-guinea
grass cropping system (sum of 7 cuts during 1976).
Treatment-/ 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
LSDo5 for chacras 1,170
LSDo5 for treatments 1,355
LSD.5 for treatments by chacras 2,346
"/Treatments are the same as those employed in 1975 (1975 Annual Report)




27
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 H2 So 04), ppm 65 143 39 91
0.M. (Walkley and Black), % 2.3 2.3 3.2 4.6
Extr. Al (N KC1), me/100Og 2.3 0.4 1.5 0.3
Exchangeable bases
Ca (N KC1), me/100Og 1.4 4.0 2.4 5.8
Mg (N KCl), me/100Og 0.6 0.4 0.4 0.4
K (N NH4 0AC), me/100Og 0.09 0.12 0.08 0.22
Na (N KCI), me/lO0g 0.08 0.08 0.02 0.24
Al saturation, % 51 4 34 4




28
Calculations on nutrient uptake by guinea demonstrated the profitability of the new 1976 grass during 1973 or 1974 showed that an in- complete treatment. The profitability could be
crease in the amount of nutrients added to the even higher if dolomitic lime is used as the Mg soil was needed. Results of the last cuttings dur- source. ing 1976 also indicated the need for this action, All of this data can be used to fit the ecoi.e., Fig. 2.2:3 shows that the difference be- nomic models that are presently being developed tween the complete and the maintenance treat- by Drs. Cate and Coutu, so a more integrated apments is, either minimal or non-existent. New proach will be given in the near future. fertility levels and lime applications were started
in January 1977. 2.3 FALLOW WITH KUDZU STUDY
Some Economical Yield Data D. E. Bandy
Some draft calculations for fertilizer profita- The traditional slash-and-burn system needs bility with the 1976 complete as compared with a 20-year fallow for the recycling of nutrients to 1975 complete are given in Table 2.2:7. Yields regenerate an exhausted soil of the Amazon of 1975 complete were taken from the 1975 jungle basin near Yurimaguas, Peru. This exAnnual Report, using the best averages in all tended time period makes it impossible for any three chacras. Thus, the cropping sequence was type of a permanent agriculture system to becalculated to yield 1,500, 1,200, and 1,600 kg come established. If, for example, the fallow of rice-corn-soybeans, respectively. Yields of period could be reduced to three or four years, a the non-fertilized checks were taken in average small farmer could permanently farm a from the three chacras. Rice yields for the 1976 five-hectare piece of land, rotating a one-hectare complete were taken from the lime-K-Mg cropping area per year with four hectares in difmicroelement satellite experiment carried out in ferent stages of fallow. a soil with initial similar chemical properties as To investigate the possibilities of using a the check plots in Chacra 1. Soybean and corn shorter fallow period, a 5-year experiment was grain yields in the 1976 complete were taken initiated in 1975 at Yurimaguas using kudzu infrom the 1976 complete treatment data pre- stead of forest for the soil regenerator. Each
sented in Tables 2.2:2 and 2.2:3. year a piece of previously farmed land, approxiThe data presented in Table 2.2:7 do not in- mately 1200 M2, is placed into kudzu fallow so clude inputs such as seeds, weeding, and insecti- that at the end of five years we will have a cides, which are considered to be equal for all chacra which has been in kudzu fallow for 4, 3, treatments. A higher hand labor requirement is 2, and 1 years. recognized to be needed at harvesting time, as At the start of the fifth year, the kudzu will
the yields increase, but is not taken into ac- be prepared for soil incorporation via several count. The table was made using the 1976 sub- methods as compared to a 20-year old forest sidized prices for fertilizers. Results clearly fallow parcel of land. The ultimate objective




29
8
CHACRA I
--6 Complete P 6 o---o Maintenance
4
0
@\~
SDFAJunANDMMJ J SODJMAMJulAS 0- 4973-o 1974 re 1975 1976 I
1*-Cut every 8 weeks-: I Cut every 6 weeks-O 6- CHACRA 2

4
0
6
JunA S N J M M JunA S 0 D J F A M Jul A S
1-*---1974 ok -1975 1976
KIcut every 8 weeks W,-Cut every 6 weeks -"I
0 8
4 Cut at 8 weeks
A J J AOND F M J J SO 0
,-- 1975 1: I1976:
- 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 replications. Yurimaguas, 1976.




30
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
Fertilization (kg/ha/yr):
N-P-K None 240-79-240 350-211-333
Mg-Cu-B-Zn-Mo None None 81-3-3-3-0.3
Extra lime (tons/ha) None 1 1
Grain Yields (tons/ha):
Rice 0.5 1.5 3.6
Corn 0.3 1.2 3.6
Soybean 0.4 1.6 2.6
Value of Crops (US$/ha/yr):
Rice 128 383 920
Corn 61 245 736
Soybean 157 629 1023
Total Income 346 1257 2679
Expenditures (US$/ha/yr):
N, P, K fertilizers 0 225 371
Mg + micronutrients 0 0 96
Lime 0 111 111
Total fertilization 0 336 578
Cultural practices 170 170 170
Harvesting, threshing 34 120 274
Crop transport to market 14 52 118
Total costs 218 678 1140
Profit
Net Profit (US$/ha/yr) 128 579 1539
$ Profit/$ invested in
fertilizers and lime -- 1.72 2.66




31
is to learn whether kudzu fallow can replace a Summary of Previous Corn Yields (1972-1975) 20-year old forest fallow, and if so, how many During 1973-1975, corn yields were exyears of kudzu fallow are needed. tremely low. In 1973, the local variety "Cuban
Another kudzu fallow system was initiated in Yellow," planted in a continuous cropping 1976 where a newly cleared chacra was inten- experiment, only yielded an average of 0.5 sively farmed for one year, using very low rates tons/ha. Severe attacks of pests and diseases as of fertilization, then placed one year in kudzu well as low levels of S, B, and Mo in the soil fallow. After one year of kudzu fallow, the area were observed. would again be intensively farmed for one year In 1974 the average yield was 1.94 tons/ha. using the same low rates of fertilization. This The corn variety Carimagua planted in the conexperiment is expected to last for at least six tinuous cropping experiment, yielded an average years, which would allow sufficient time to of 1.7 tons/ha and a maximum yield of 3.1 study the changes in the physical and chemical tons/ha using the following fertilizer rates: properties of the soil after three years of farm- 80-44-66 kg/ha of N, P, K plus 0.5 kg/ha of B ing interspaced with three years of kudzu fallow, and Mo, and 3.5 tons/ha of lime. These mediocre yields were attributed to the low genetic
2.4 VARIETIES AND SOME AGRONOMIC potential of the variety utilized and to pest and
FACTORS OF CORN PRODUCTION STUDIES disease problems. In 1974, the best average yield
J. R. Benites and G. C. Naderman was obtained with the variety Amarillo Planta
Prior to the initiation of the intercropping-N Baja (3.2 tons/ha), planted in the N x spacing experiment, it was necessary to obtain consis- experiment, and a maximum yield of 4.0
tent information on the corn crop, since at the tons/ha was obtained with the following fertilearly stage of the research in Yurimaguas corn izer rates: 180-51-120 kg/ha of N, P, K plus was identified as a problem crop. After evaluat- 10 kg/ha of S, 0.5 kg/ha of B, 0.53 kg/ha of Mo, ing corn yield data obtained in the different and 0.9 tons/ha of lime. experiments conducted from 1972 through In 1975 the mean yield was 2.0 tons/ha. The
1975, it was decided to try those corn varieties variety PD (MS)6 planted in continuous cropand hybrids obtained by the Corn Program of ping experiment, yielded an average of 0.7 the National Agrarian University (UNA) and tons/ha and a maximum of 1.9 tons/ha. The
CIMMYT for tropical areas. Together with the climatic conditions during this planting season study of genetic material (considered to be the were not favorable, and the availability of soil first limitation) an attempt was made to learn nutrients was low. A yield of 5.8 tons/ha was about the response of these varieties to fertiliza- obtained during 1975 with the hybrid PM-211 tion, plant population and other agronomic in the macro- and micronutrients experiment.
factors.




32
But the same hybrid planted in the same season Results. Table 2.4:1 presents yields of the in the P-S interaction experiment, only reached varieties that reached more than 1.5 tons/ha, ina mean yield of 0.7 tons/ha, and a maximum of cluding the local variety for comparison. Yields 1.5 tons/ha obtained with the formula of all varieties increased with fertilization and 120-53-100 kg/ha of N, P, K plus 60 kg/ha of S liming; the varieties Amarillo Planta Baja, and 1.4tons/haof lime. PM-211, 1268 x 1273 (C11 x C16), and
In summary, all possible factors that could Tuxpe6o Braquitico Blanco responded most to have influenced corn yields during 1973-1975 fertilization and liming with yield increases of did. These were genetic, agronomic, climatic, 46%, 56%, 55%, and 56%, respectively. The local and pests. variety gave only a 17% yield response to liming
Corn Varietal Response to Liming and and fertilization.
Fertilization The highest yield at both fertility levels was
Objectives and design. In earlier experiments obtained with the variety Amarillo Planta Baja. maximum yields generally have been associated This variety also gave one of the highest rewith the high fertility levels but there was no sponses to liming and fertilization with a 46% certainty that genetic material with the highest yield response. By comparing the yields of imyield potential was used. This experiment con- proved varieties with the local variety in the sisted of a test of 22 tropical varieties and higher fertility treatment, it can be observed hybrids from the germplasm bank of the corn that Amarillo Planta Baja, 1268 x 1273, PM-211 program of the National Agrarian University. and PMS-264 were superior producing respective
Before treatment the first 15 cm of soil con- yield increases of 113%, 88%, 74% and 70%.
tained 2.24 me and 3.03 me of Al and Ca + Mg, During the experiment a strong insect, disease
respectively, per 100g of soil and 43% Al satura- and bird attack occurred and it was observed tion. Each variety was planted at two fertility (Table 2.4:2) that the highest proportion of levels (indicated as lime-N-P-K in kg/ha): damage occurred in low-lime plots, although in
1. 500-0-00 both cases the proportion was high. Table 2.4:3
2. 1500-180-66-83 shows some growth variables, such as plant
Lime and P were applied during soil prepara- height, precocity and susceptibility to lodging. tion 15 days before planting. The N was banded The tallest plants were PMS-264 (2.83 m) and beside the plants and was split into three equal the local variety Cuban Yellow (2.87 m). The portions at 15, 30 and 45 days after planting. medium-height varieties were PM-211 (2.64 m), Applications of K and Mg were made at 15 days and Hibrido Tropical (2.67 m). The shorter variafter planting. Atrazine was applied at 2 kg/ha eties were Amarillo Planta Baja and Tuxpeno for weed control. The crop was planted April 21 Braquitico Blanco with 2.33 m and 2.18 m, and harvested after 102-114 days. respectively. The hybrid PM-21 1 showed lodging




33
Table 2.4:1. Yield response of 10 corn varieties to lime and fertilization,
Yurimaguas, 1976.
Yield response to Comparison
Corn grain yield lime and with local
fertiliza- variety (both
Variety Low Lime Only Lime + Fert. tion rec'd fertil.)
---------- tons/ha-------- % % increase
POB II 1.73 2.60 33 44
PMS-264 1.85 3.07 40 70
Amarillo Planta Baja 2.09 3.86 46 113
PD(MS)6 1.79 2.48 28 37
PM-211 1.39 3.14 56 74
PMC-747 2.03 2.88 30 59
Hibrido Tropical 1.51 2.59 42 43
Tuxpeho Braquitico Blanco 1.01 2.32 56 28
1268 x 1273 (C11 x C16) 1.52 3.40 55 88
Cuban Yellow (local variety) 1.51 1.81 17 -LSD.05 Between varieties at the same fertility level: 1.08 LSD.05 For one variety at different fertility levels: 1.62 CV: 38%




34
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, peanuts and rice. Yurimaguas, Peru. March, 1977.




35
Table 2.4:3. Some phenotypic variables of corn in the variety x fertilization 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 -Tuxpeio 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)
2
correction for temperature above 86 'F was made.




36
susceptibility with 9% of the plants lodged at 73 with the first half of N. Harvest was 126 days days after planting and 50% at harvest time. In after planting. contrast were the varieties Amarillo Planta Baja Results. Table 2.4:4 shows that yields of all and Tuxpeho Braquitico Blanco, which showed varieties but one increased as the population inzero lodging both at 73 days and at harvest time. creased from 44,000 to 53,000 plants per Finally, the earliest maturing varieties were hectare. The varieties PMS-264, PD (MS)6 and PD (MS)6 and Amarillo Planta Baja and the PMC-747 significantly responded to the higher
latest maturing varieties were Cuban Yellow and population with yield increases at 35%, 27%, Tuxpen-o Braquitico Blanco as determined by and 25%, respectively. However, the yield of cumulative heat units at silking. Tuxpeno Braquitico Blanco decreased by 69% as
Varieties and Plant Population Studies with plant population increased. Corn With respect to variety effect, Hibrido TroObjectives and design. The experiment on pical had an exceptionally high yield of 6.49
varieties and plant population conducted in tons/ha which greatly exceeded yields of the 1975 showed that as plant population was in- other varieties. However, Hibrido Tropical and creased from 55,000 to 66,000 per hectare, other corn hybrids were badly affected during
yields tended to diminish, both in the fertilized the dry season, especially at the low fertility + limed and low limed treatments. For this level. Due to this consideration, for further reason in 1976, an experiment was installed, studies we preferred the composite variety which had 44,000 and 53,000 plants per hectare Amarillo Planta Baja which exhibited a tolerance as population treatments. Both populations were to dry season and wet seasons in low and high planted at the same fertilization level fertility levels. (160-66-125 kg/ha of N-P-K plus 18 kg/ha of Planting Date Effect on Corn Grain Yield Mg and 2 tons/ha of lime). The most promising The influence of planting date and associated corn varieties from the variety and fertilization environmental factors is apparent by comparison experiment were utilized, including the local of the yields of two experiments previously revariety Cuban Yellow as check. Corn was ported. The variety x fertilization study was
planted in September in Chacra IV. planted in April, and the variety x plant populaThe population of 44,000 was obtained by tion study was planted in September 1976.
planting rows of 0.90 with 0.25 m between Results of this comparison are presented in
plants. The 53,000 population was obtained Fig. 2.4:1. Yields of corn planted in September
with rows at 0.75 cm and 0.25 cm between were 43% greater than those of corn planted in
plants. Half of the N was applied 10 days after April. Varieties having the greater yield increases planting with the balance at 30 days. Lime and P from September planting were Hibrido Tropical, were applied during land preparation prior to PD (MS)6, PMC-747, POB-1 1 and PMS-264. planting. All K and Mg were applied together




37
Table 2.4:4. Plant population effect on grain yield of 10 corn varieties
planted in September 1976. Yurimaguas.
Plant population, plants/ha 40,000 50,000
Yield Yield Yield
compared compared response
with with to
Grain local Grain local high
Variety yield variety yield variety population
tons/ha % change tons/ha % change % change
POB II 4.24 8.7 4.81 20.3 11.9
PMS-264 3.51 -10.0 5.42 35.5 35.2
Amarillo Planta Baja 4.14 6.2 4.72 18.0 12.5
PD (MS)6 3.74 4.1 5.09 27.3 26.5
PM 211 4.57 17.2 5.02 25.5 9.0
PMC-747 4.17 6.9 5.52 38.0 24.5
Hibrido Tropical 5.94 52.3 6.49 62.3 8.5
Tuxpefo Braquitico 5.34 36.9 3.16 -21.0 -69.0
Blanco
1268 x 1273 (C11 x C16) 4.07 4.4 4.81 20.3 15.4
Cuban Yellow (local 3.90 -- 4.00 -- 2.5
variety)
Mean 4.30 4.91
LSDo5 Plant population: 1.34 tons/ha LSD05 Varieties: 0.95 ton/ha CV: 15%




38
7.0- lanting Date ..
.S05 22 Apr.
6.0-M 20 Sep.
Co5.0o4.0
w
z
0 2.01.0
0M _j M- qt 0 < -30 -0
IM 0 r.- 02 wO~ oZ ~
0 CO UO I Cn U.CL-Z
a. 0j.. in C 0 )( W>0
a.~~L Zi 1.r) 0 O
. a: N '
Figure 2.4:1. The effect of planting date and associated environmental
factors on corn yields in Yurimaguas, 1976.




39
Table 2.4:5 shows some of the average re- 0.75 m, planting systems of "drilling hill" (one
suits of various climatic observations during the plant each 0.25 m) or "dropped hill" (three growth of both crops. In September, the precipi- plants each 0.75 m), and no, one or two hillings. tation more than doubled that of the April The combination of these factors gave 12 treatplanting; furthermore, between June and July, ments for each variety. For all treatments, the 51 cumulative days and more than 10 consecu- following fertilization formula was utilized:
tive days without rain were reported. It appears 160-66-83 kg/ha of N-P-K plus 18 kg/ha of that this dry period during the first planting Mg and 2 tons/ha of lime. Planting was accordfavored the increase of corn pests (Table 2.4:6), ing to treatment. First and second hillings were especially during the flowering and maturation 15 and 30 days after planting. Nitrogen was split process, which affected yields adversely. On the into two equal applications, and in each case beother hand, during the September planting there fore the hilling process. Harvest was 120 days was sufficient precipitation with normal distri- after planting. bution patterns. Results. Table 2.4:7 shows the yields obCumulative solar radiation was higher in tained with the variety Amarillo Planta Baja. It
the September than in the April planting. This can be noted that the hilling practice increased factor may have influenced the yield-producing the yields from 4.90 tons/ha (without hilling) to potential per hectare in September because this 6.60 tons/ha (with one hilling), utilizing a row period received more solar radiation available for spacing of 0.75 m. With a row spacing of 0.90 m photosynthesis. there were no differences in yields between oneAll these data demonstrated that the planting hilling and no-hilling, but with two-hillings there date had a large influence on corn yield. Good was a significant increase in yields. There were varieties with an adequate level of fertilization no differences found between planting systems may fail if planted during the wrong planting and row spacings. season. The hybrid PM-211 had a mean yield lower
Planting System, Row Spacing and Hilling than that of Amarillo Planta Baja. None of the
Objectives and design. The objective of this factors being studied significantly affected the experiment was to determine if the utilization of yields of this hybrid and thus, the results obhilling and a better distribution of plants in the tained with this hybrid are not presented in this land could increase the efficiency of fertiliza- report. tion, as well as to determine if they could reduce Stalk-Doubled Over Effect on Corn Grain Yields plant lodging. Objectives and design. During the drier season,
This experiment was installed in Chacra II1. there is a high incidence of bird and insect damThe varieties Amarillo Planta Baja and the age to corn. In the rainier season, damage is
hybrid PM-21 1 were utilized. The treatments for caused by disease. In both cases, yields can be each variety were row spacings of 0.90 or reduced up to 50%. A common practice utilized




40
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/grI/cm-2 39.9 49.8
Average temperature1I (00 25.2 26.5
Average maximum temperature (C) 30.5 32.2
Average minimum temperature (C) 20.9 20.5
1/
Average relative humidity- (%) 83.3 78.8
Average standard P.A.N. evaporation (mm) 3.4 2.5
-/Average temperature and average relative humidity are based on the daily
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.




42
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 No hilling 5.54 4.25 4.90
One hilling 6.60 6.60 6.60
Two hilling 5.18 6.16 5.67
Mean 5.77 5.67 5.72
90 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
Mean No hilling 5.14 4.05 4.60
Row Spacing
One hilling 6.49 5.12 5.81
Two hilling 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%




43
by small farmers of the tropics in order to avoid was not limed since 1.5 tons/ha of lime had been these problems is "stalk doubling." The objec- applied at the previous planting. Planting was at tive of this experiment was to determine if this a population of 50,000 plants per hectare is an agronomically sound practice and to deter- (0.90 m between rows and 0.60 m/3 plants). mine which is the best time to perform it. The Results.The varieties Mezcla Tropical Blanca,
stalks were doubled at four weekly intervals, (Ver. 181-Ant. Gpo. 2) 02, and La Posta were with the first beginning 20 days after silking. the only ones that significantly out-yielded the
This experiment was installed with a Cuban check variety Cuban Yellow (Table 2.4:9). The
Yellow seed planted in June. The plot received varieties Tuxpe6o 1, Braquitico, Yellow H.E.02 only 50 kg/ha of N and 500 kg/ha of lime. The and Tuxpeio Caribe-1 yielded less, but not signistalk doubling was made below the principal ear. ficantly than the local variety. Harvest was 41 days after silking. General Conclusions. Genetic material has a
Results. In Table 2.4:8 it can be noted that great influence on corn yield. However, good stalk doubling did not affect the yields even varieties with adequate fertilization may fail if though stalks were doubled beginning 20 days planted during the wrong planting season.
after the beginning of the silking stage. The The corn variety Amarillo Planta Baja had
humidity percentage was 60.1% at the time of the best overall yields in the various trials. It
the first stalk doubling, and 23% at harvest. It is ranked first in the fertilizer and liming treatpossible that the early utilization of this practice ments (3.86 tons/ha), as well as in the treatment could help corn avoid the consequences of ad- without fertilizer and low-levels of liming (2.09 verse climatic conditions which may favor pest tons/ha). Yields obtained in the dry season and disease infestation and also may reduce the (April planting) and the rainy season (September negative effect on shorter plants (rice, peanuts, planting) were favorable compared to those of soybeans) that may grow intercropped with hybrids and other varieties which were badly afcorn. However, this supposition must be further fected during the dry season. In addition, the tested before a conclusive statement can be relative shortness of this variety (2.3 m) makes it
made. resistant to lodging. On the other hand, Amarillo
Tropical Corn Varieties and Hybrid Trials from Planta Baja is an early variety, which silks in ClMMYT 50 to 58 days, and matures in 90 to 100 days,
Objectives and design. In August 1976 corn making it possible to harvest with a 20-25%
seeds were received from CIMMYT which were grain humidity. Due to its earliness, this variety
planted in September in Chacra IV, with the can be planted up to three times a year, with a
purpose of expanding the information on potential grain yield of more than 10 tons/ha/
genetic material adapted to the tropics. year.
This experiment was fertilized with
160-44-83-18 kg/ha of N-P-K-Mg. The soil




44
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
LSD05: 1.08
CV: 30%




45
Table 2.4:9. Yield parameters of 22 CIMMYT tropical corn varieties. September, 1976. Yurimaguas.
Grain
Stover
Varieties Grain Stover Dry Matter Ratio
---------------- tons/ha------------------Tuxpeo-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
Tuxpefio 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




46
2.5 PHOSPHORUS AND SULFUR STUDIES Results. Table 2.5:1 also presents yields of
J. H. Villachica and P. A. Sanchez rice and soybeans harvested during 1976. Rice
Objectives and design. The basic idea for per- yields with the first nine treatments, fertilized forming this research was outlined in the 1975 with RP, but no lime, were very low. In all of Annual Report. First crop yields (corn) were re- the first nine treatments except those of 7 and ported at that time. The same plots were used to 9, yields were 0.5 ton grain/ha or less. Data prestudy residual effects of the lime, P, and S ini- sented in Table 2.5:2, with soil samples taken tially applied. Rice was used as the test crop, before planting, indicate that these very low and following its harvest, new rates of super- yields were limited by the high amounts of exphosphate and rock phosphate were applied changeable Al and the high percentage of Al satprior to soybean planting. Table 2.5:1 shows the uration in the soil. In fact, Al toxicity symptoms distribution of rice treatments. Treatments 1 were easily identified on rice plants growing on through 15 were used to test the residual effect these plots. These high Al contents were exof P, employing three and two rates of rock plained by the lack of lime application to the
phosphate (RP) and triple superphosphate soil and by the history of the field. All three rep(TSP), respectively. Treatments 16 and 17 were lications were former bulldozed plots which reused to determine whether the S contained in ceived no lime initially, neither from ash nor the superphosphate (SSP) would provide the S from liming material. Data presented in Table needed by the plants. Treatment 18 was a check. 2.5:11 indicated that even though a high available Treatments 19 and 20 were used to test if RP P content (Olsen method) was built up in the applications prior to those of SSP would com- soil, such as in treatments 7, 8, and 9, rice would pensate for the use of lime in this very acid soil. not grow adequately unless Al toxicity was neuAll treatments were applied prior to corn plant- tralized. As it will be discussed later, this was ing, as reported in the 1975 Annual Report. noted also for soybeans.
After corn was harvested, rice (cv. IR-4-2) was Figure 2.5:1 shows the difference between planted on November 29, 1975, with no addi- rice yields as determined by residual effects of
tional P, S, or lime. Following the rice harvest RP and those of TSP plus 1.4 tons lime/ha. of April 14, 1976, new levels of RP, TSP, SSP, Yields of rice averaged over 1.3 tons/ha in the and lime were applied on April 25, as described treatments where residual effect of the two in Table 2.5:1. Soybeans (cv. XLM) were levels of TSP was noted. Differences due to the planted on May 11, 1976. A basal application of residual effect of S were not significant. 120 kg N/ha and 100 kg K/ha was applied for Rice yields on residual SSP plots (treatments
rice. Soybeans received only 30 kg N/ha and 16 and 17) were similar to those on all residual
100 kg K/ha. Soybeans were harvested on TSP plots, both with and without S. Thus, a reAugust 30. sponse to residual S was not evident in the rice




47
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------1 RP 26 0 0 218 0 48 237 240
2 RP 26 30 0 218 0 10 302 308
3 RP 26 60 0 218 0 130 449 352
4 RP 52 0 0 327 0 330 215 299
5 RP 52 30 0 327 0 95 121 419
6 RP 52 60 0 327 0 14 167 417
7 RP 208 0 0 436 0 1,280 956 793
8 RP 208 30 0 436 0 911 309 480
9 RP 208 60 0 436 0 624 556 841
10 TSP 26 0 1.4 26 1.0 1,068 1,229 1,262
11 TSP 26 30 1.4 26 1.0 1,300 1,793 1,255
12 TSP 26 60 1.4 26 1.0 531 1,538 1,037
13 TSP 52 0 1.4 52 1.0 1,055 1,567 1,258
14 TSP 52 30 1.4 52 1.0 1,330 1,538 1,202
15 TSP 52 60 1.4 52 1.0 1,540 1,751 1,262
16 SSP 26 0 1.4 26 1.0 1,324 1,583 1,085
17 SSP 52 0 1.4 52 1.0 1,430 1,542 1,217
18 NONE 0 0 0 52 2.0 0 349 857
19 SS+RP 26SSP+26RP 0 0 26SS+436RP 0 210 609 551
20 SS+RP 26SS+183RP 0 0 52SS+436RP 0 1,203 709 629
LSD.05 461 709 358
-/Planting dates for corn, rice, and soybean were July 1975, November 1975,
and May 1976, respectively.




48
Table 2.5:2. Some soil chemical properties on P and S plots sampled in November 1975. (Average of two replications)
Mod.
Olsen 6N H2So4 1N KCI extract. Al
Tmt P K pH O.M. Al Ca Sat.
ppm ppm % ---- me/lOOg---- %
1 6 52 4.0 2.5 2.1 0.7 64
2 4 50 4.3 2.2 3.0 1.8 57
3 6 58 4.0 2.5 2.9 0.9 67
4 10 55 4.0 2.4 2.6 1.3 59
5 8 48 4.0 2.6 2.9 1.0 66
6 7 65 3.9 2.1 3.1 0.8 70
7 24 44 4.4 2.5 3.1 1.2 65
8 28 52 4.2 2.8 2.2 1.4 54
9 27 65 4.3 2.5 1.7 1.8 43
10 5 52 4.7 2.7 1.0 3.0 22
11 5 65 4.7 2.4 0.7 2.9 17
12 4 52 4.4 2.2 2.5 2.3 50
13 8 52 4.7 2.0 2.1 2.5 41
14 7 65 4.4 2.3 2.3 2.7 42
15 12 44 4.7 2.8 0.5 3.3 12
16 3 39 4.6 2.5 1.3 3.1 27
17 6 44 4.7 2.3 0.9 3.2 20
18 4 65 4.1 2.4 2.2 1.5 52
19 11 65 4.1 2.5 2.4 1.6 53
20 27 50 4.2 2.6 1.4 1.5 41




49
P
(kg/ha)
2.0 aS:
D, 120TSP
- ~1.6
;--- -- 6 60 TSP
- 0.80 480 RP
S -60RP
0.8
w 480 RP
S20.4 _A60RP
120 RP
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.




50
yields. Neither did the following crop of soy- 2.6 MICRONUTRIENT RESEARCH beans show a response to the residual S of SSP. J. H. Villachica and P. A. Sanchez Considering the low rice yields obtained Experiment 1. Responses to Lime, K, Mg and with the RP treatments, higher levels of RP were Micronutrients. used (Table 2.5:1) to determine if Al toxicity Objectives and design. Preliminary results on problems could be alleviated in this way. Fifteen secondary and micronutrient studies reported in days prior to soybean planting, RP or TSP plus the 1975 Annual Report showed a strong re1 ton lime/ha were applied. No further additions sponse of corn and soybeans to lime and magof S were made except where SSP was applied nesium and a good response of soybeans to with lime or with RP (treatments 16-20). foliarly-applied micronutrients. Both studies
Soybean grain yields follow a similar pattern were continued to determine the residual effect to that described for rice (Table 2.5:1). Thus, of lime and Mg and the effect of new applicayields on the plots that received lime plus either tions of K and micronutrients. Both crop seTSP or SSP were higher than those that received quences (soybeans-rice-corn and corn-riceonly RP. However, soybean yields on plots 7 soybeans) were planted with rice (cv. IR-4-2) on and 9, where a total of 644 kg P/ha as RP were November 24, 1975, and harvested on April 7, applied during the entire study, were not too 1976. Corn (cv. PM-211) and soybeans (cv. different from those of the plots that received National) were planted on April 23, 1976, after TSP or SSP, i.e., treatments 12 or 16. rice was harvested. Soybeans were lost due to
Lack of difference between treatments 16 herbicide residual effect. Corn was harvested on and 17 (those that received SSP) and treatments August 23, 1976. Before each sowing of rice or 10-15 (those that received TSP) indicated that S corn, K was applied in the amounts shown in was not limiting yields at this time. It should be Table 2.6:1. A basal application of 150, 70, and pointed out that in addition to Al, other limiting 22 kg N, P, S/ha, respectively, was made in all problems in this experiment were believed to be plots. Micronutrients were twice sprayed on the Mg deficiency and the low amount of N applied leaves: at 45 and 67 days for rice, and at 20 and for rice. Magnesium deficiency was proved to be 40 days for corn. Residual effects of lime (apa limiting factor on soils of the area at the time plied May 23, 1975) and Mg (applied June 25, soybeans were planted, but it could not be cor- 1975) were studied. A composite rotable design rected because the only two available Mg fertil- of treatments as presented in Table 2.6:1 was izers were Mg sulfate and K-Mg sulfate, both of used. which are also sources of S.




51
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 2/ Grain Yields
Micro- Corn-Rice-Soybean Soybean-Rice-Corn
nutrient Sequence Sequence
No. Lime K Mg Level./ Rice Rice Corn
t/ha --kg/ha-- kg/ha------------1 1 83 9 1 3112 2644 1656
2 3 83 9 3 3538 2882 5239
3 1 166 9 3 3224 1516 148
4 3 166 9 1 4190 3462 3529
5 1 83 27 3 4117 822 3224
6 3 83 27 1 4880 2536 4056
7 1 166 27 1 2731 2940 2075
8 3 166 27 3 3187 3530 4309
9 1 83 9 3 3336 3094 428
10 3 83 9 1 4060 4262 3926
11 1 166 9 1 2964 2948 148
12 3 166 9 3 4638 4322 3650
13 1 83 27 1 3603 2552 1524
14 3 83 27 3 3496 4328 4890
15 1 166 27 3 3244 2912 1192
16 3 166 27 1 4544 2986 2779
17 0 0 0 0 802 380 1
18 2 125 18 2 3670 3662 3281
19 0 125 18 2 3236 2162 138
20 4 125 18 2 3726 3796 5273
21 2 41 18 2 3100 2814 3529
22 2 208 18 2 3384 3804 3592
23 2 125 0 2 3562 2910 1617
24 2 125 36 2 3502 2787 3658
25 2 125 18 0 3974 2678 1278
26 2 125 18 4 3586 3270 5301
1/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 before each planting. Micronutrients were applied two times as spray
during the growing period.
.!/Micronutrient level 1 was: two sprays of a solution of 22 g zinc sulfate, 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 micronutrients were 2, 3, and 4 times level 1, respectively.




52
Results. Yield response of rice to the dif- Rice yield response to micronutrients was
ferent treatments and in both crop sequences is found only on those plots that had a previous shown in Fig. 2.6:1. A response to the residual crop of soybeans. In these cases, the yield diflime can be observed in the experiment where ference between the treatment that received rice was planted after soybeans. The response micronutrient level 2 and that not receiving was lower in the companion experiment. From micronutrients was 984 kg/ha.
the data of Fig. 2.6:1, it seems that lime and K To continue studying the residual effect of were the most limiting factors for rice produc- lime and magnesium, corn was planted next in tion in this soil. the sequence soybeans-rice-corn. Potassium
Table 2.6:2 presents some soil chemical was applied before planting and micronutrients
properties in soil samples taken before rice was were applied foliarly at 15 and 35 days at rates planted (corn-rice-soybeans sequence). It can given in Table 2.6:1. Corn (cv. PM-211) was be observed that pH was 4.3 in the unlimed used.
plot, 4.6 where 2 tons lime/ha were applied five Corn yields as influenced by treatment are months earlier, and 5.6 where 4 tons lime/ha given in Table 2.6:1 and Fig. 2.6:2. A very drawere applied also five months earlier. Similarly, matic response of corn to the residual effect of Al saturation decreased from 48% to 24% and lime can be observed in Fig. 2.6:2. Corn yields
9%, respectively. This evidence indicated that were almost nil in the unlimed plots but foleven though pH was low in the plots that re- lowed a linear response to the residual effect of
ceived 2 tons lime/ha initially, Al saturation was the lime initially applied. No yield plateau was not sufficiently high to cause problems for rice. reached. The initially-applied 1 ton lime/ha level Yields of rice on the fertilized plots that were which gave those good soybean yields eight limed initially with 2 tons lime/ha or more months earlier no longer provided adequate soil
averaged 3.5 tons grain/ha. This yield was con- conditions for corn growth. Yields over 4 tons sidered excellent for upland rice growing in this grain/ha were obtained only with the residual efold abandoned soil with very low native soil fer- fect of 3 or 4 tons lime/ha applied at the begintility. ning of the experiment. The experiment was
Response to K of rice following corn exhib- limed on May 23, 1975, and then soybeans and ited the same pattern as did the previous crop. rice were grown successfully up to April 1976. Thus, the maximum response was to 83 kg K/ha. Thus, the residual effect of 1 ton lime/ha lasted When rice was planted after soybeans, the only about ten months. The residual effect of
highest yield was observed with 125 kg K/ha. No 2 tons lime/ha was noticeable, but reduced. This clear response to the residual effect of Mg was fast depreciation of the residual effect of lime found. Rice growing after soybeans (SAM ex- can be explained by the high leaching conditions
periment) showed only small yield response to in Yurimaguas which moved Ca into the subsoil residual Mg. Rice planted after maize (MAS ex- (Villachica, Ph.D. Dissertation, 1978) and on the periment) did not show response to residual Mg. lime source used. Lime source used was calcium




53
4
41 Woo-*o 2
0- Rice after Soybean
(SAM)
0 e-9 Rice after Maize (MAS)
I -III I I I
O I 2 3 4 41 83 125 166 208
C')
W LIME APPLICATION (tons/ha) K APPLICATIONS (kg/ha)
Z
4
2
O 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 application of K and micronutrients and the residual effects of lime
and Mg. Yurimaguas, 1976.




54
Table 2.6:2. Some soil chemical properties on the secondary and micronutrient experiment with the corn-rice-soybean sequence.
Yurimaguas, October 1975.
Amounts Applied-/ Available-2 Exchangeable
Micro.
Tmt. Lime K Mg spray P K pH K Ca Al
T/ha --kg/ha-- --ppm--- ---- me/lOOg------1 1 83 9 1 11 65 4.4 .11 2.2 .70
2 3 83 9 3 8 65 4.7 .11 2.8 1.20
3 1 166 9 3 16 137 4.8 .30 2.2 .90
4 3 166 9 1 13 156 5.2 .30 2.8 .20
5 1 83 27 3 12 91 4.7 .20 2.6 .60
6 3 83 27 1 6 65 5.3 .12 4.0 .20
7 1 166 27 1 6 72 4.4 .16 2.6 1.10
8 3 166 27 3 6 78 4.8 .16 3.8 1.00
9 1 83 9 3 11 59 4.8 .13 2.0 .50
10 3 83 9 1 7 78 5.0 .14 3.2 1.30
11 1 166 9 1 6 78 4.6 .19 2.0 .40
12 3 166 9 3 10 98 5.2 .22 2.6 .50
13 1 83 27 1 8 65 4.6 .14 2.0 1.00
14 3 83 27 3 5 65 4.8 .13 3.3 .90
15 1 166 27 3 8 91 4.6 .17 2.0 .40
16 3 166 27 1
17 0 0 0 0 10 65 4.4 .16 1.6 1.50
18 2 125 18 2 7 56 4.8 .14 2.0 .90
19 0 125 18 2 6 78 4.3 .14 1.4 2.00
20 4 125 18 2 7 78 5.6 .14 4.2 .50
21 2 41 18 2 8 65 5.0 .15 3.0 .50
22 2 208 18 2 4 98 5.0 .28 3.0 .60
23 2 125 0 2 12 130 5.1 .35 2.8 .40
24 2 125 36 2 11 98 4.9 .18 2.6 .70
25 2 125 18 0 4 65 4.9 .11 2.2 1.00
26 2 125 18 4 5 65 4.6 .14 2.4 1.00
lAmounts of amendments applied in June 1975. Micronutrients refers to
foliar spray of micronutrients as explained in Table 2.6:1.
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 KCI.




55
6
4
c2
O
(I I I I I I I I
0 I 2 3 4 41 83 125 166 208
Cl)
C) LIME APPLIED INITIALLY K APPLIED (kg/ha)
w( t/ha) Z 6S4
z
2
II I I I I I
0 9 18 27 36 I 2 3 4
Mg APPLIED INITIALLY LEVEL OF MICRONUTRIENT
(kg / ha) SPRAY
Figure 2.6:2. 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.




56
hydroxide of which 100% passed through a with 4 tons/ha lime as Ca(OH)2. For practical 2 mm sieve. Calcium hydroxide is known to be considerations and for a 13-month cropping severy reactive in the soil and to have a short re- quence of soybeans-rice-corn or any combinasidual effect. tion thereof, an initial application of 3 to 4 tons
The next most limiting factor for corn grain lime should be considered. Since the residual efyield was micronutrients. Fig. 2.6:2 shows that fect of lime is lost so quickly, soil acidity should when micronutrients were not applied, corn be checked at least once a year in order to congrain yields were slightly over 1 ton/ha, and with sider application of additional lime. It was also the application of two foliar micronutrient pointed out that Mg and micronutrients became sprays, increased up to 5 tons/ha. That corn re- more limiting after two crops had been removed sponded more dramatically to micronutrients from the field. These data partially explained than did soybeans could be due to differential the rapid yield decline in the continuous cropcrop species response and to a decrease in the ping experiments. It also was suggested that amounts of micronutrients originally present in yields in the continuous cropping experiments the soil. Thus, it is expected that when the soil is would not have been improved as well this year under continuous cropping, micronutrient re- if only the new levels of lime and NPK were apsponses or deficiencies will be bigger after sev- plied. Magnesium and micronutrients were eral crops have been harvested, needed also. The need for the study of new limNo corn response was observed between 42 ing materials that carry Mg and will have higher to 208 kg K/ha. This result, when compared residual effects is emphasized.
with those obtained in the first crops, suggested Experiment 2. Soybean Responses to Lime, Mn, that K was not a limiting element in this range B and Mo. of application, although it was found in very low Objectives and design. Soybean response to levels in the soil (0.15 me K/100 ml). Magne- micronutrients was observed in the experiments sium residual effects were more limiting than K. conducted during 1975 and early 1976 in an old Yields of corn increased up to 3.1 tons grain/ha abandoned field (1975 Annual Report). Howwith the residual effect of 18 kg Mg/ha. Soils ever, all micronutrients were applied as a foliar and plants have been sampled, and chemical spray. There was no information on which of
analyses are being performed. These data will the elements was or were responsible for the inhelp to explain some of the responses observed. crease in yields. Soybeans growing during 1975
A very important conclusion drawn from in Chacra 3 showed symptoms that resembled
these experiments is that 1 ton lime/ha did not Mn deficiency. Foliar analysis of soybean samlast more than ten months; 2 tons lime had a pies taken from this field indicated low levels of little higher residual effect, but yields were Mn, B, Fe, Mg, and Ca in the leaves. For this realower than those obtained with 3 tons lime/ha, son, a portion of Chacra 3 that was burned in The best yield results for all crops were obtained 1974 and then abandoned again was cleared and




57
planted with soybeans (cv. XLM) in July 1976. (treatment 17), soybean yield was only 1.5 Five levels of lime, Mn, B, and Mo were studied. ton/ha, even though all other micronutrients The amounts of nutrients studied are presented were applied. This result agreed with that found in Table 2.6:3. in greenhouse experiments and reported in the
Results. Table 2.6:3 and Fig. 2.6:3 present 1974 Annual Report that Cu is limiting crop soybean grain yield as affected by the applica- yields in soils of Yurimaguas. tion of the different treatments. There was a re- In summary, the evidence indicated that in a sponse to 1 ton lime/ha as soybean yields in- newly cleared and burned chacra that has not creased from 1.5 ton/ha to 2.5 tons/ha (Fig. been cropped, Mo, Mn, Zn, and Fe were ade2.6:3). No further response was found to addi- quately supplied to the plant. Boron seemed to tional lime applications up to 4 tons lime/ha, be needed in low amounts (0.5 kg B/ha), and apThis result differed somewhat from that re- plications of 2 kg Cu/ha were also necessary. ported last year in the secondary and micronu- Experiment 3. Peanut Response to Cu, Mn, B trients study, where soybeans were reported to and Mo. respond up to 2 tons lime/ha. This could be ex- Objectives and design. Secondary and microplained by the low Al saturation of the soil in nutrient studies reported in 1975 showed a soyChacra 3, possibly due to some liming effect bean response to foliar applications of microelefrom the ash (1974 Annual Report). ments. The soil in which soybeans were grown
No positive response was observed to either was a very low fertility soil from an old abanfoliar Mn applications or Mo seed treatment, in- doned pasture. No beneficial effect of ash was dicating that both elements were present in ade- expected here. As previously emphasized, the quate amounts in the soil or that some other experiments with foliar micronutrients were defactor was more limiting to yields. With respect signed only to detect whether there was reto B, soybean grain yields increased about 0.5 sponse to microelements. No information was ton/ha when the first 0.5 kg B/ha were applied, obtained at that time with respect to which However, when additional 0.5 kg B/ha rates micronutrient was deficient and what should be
were applied, soybean yields dropped to those the amount to be applied to the soil. of the zero B level. Research in Georgia on sim- Peanuts were incorporated into the crop seilar soils has indicated B toxicity to soybeans at quences being studied in continuous cropping rates greater than 1 kg/ha. experiment, since they have a high cash value
Additional treatments of soil-applied Zn and and are very promising in the area. However, in foliar applications of Fe were used to test the re- almost all of the experiments in which peanuts sponse of soybeans to these elements. Table were studied, plants were characterized by a 2.6:3 shows that there was no response to either high number of empty pods at harvesting time. one of these treatments (treatments 27 and 28). Empty pods are known to be one of the sympHowever, when Cu was not applied as basal toms of B deficiency. Chemical analysis indi-




58
Table 2.6:3. Soybean grain yields as affected by lime, Mn, B and Mo appl icationsl/.
Amounts Applied
Soybean
Tmt. Lime Mn B Mo Remarks2/ Yield
T/ha kg/1000 1/ha kg/ha g/kg kg/ha
seed
1 1 0.5 0.5 1.5 2333
2 3 0.5 0.5 4.5 1845
3 1 1.5 0.5 4.5 2591
4 3 1.5 0.5 1.5 2493
5 1 0.5 1.5 4.5 2602
6 3 0.5 1.5 1.5 2426
7 1 1.5 1.5 1.5 2941
8 3 1.5 1.5 4.5 2131
9 1 0.5 0.5 4.5 2808
10 3 0.5 0.5 1.5 2283
11 1 1.5 0.5 1.5 2823
12 3 1.5 0.5 4.5 2720
13 1 0.5 1.5 1.5 2051
14 3 0.5 1.5 4.5 1767
15 1 1.5 1.5 4.5 2230
16 3 1.5 1.5 1.5 2567
17 2 1.0 1.0 3.0 Minus Cu 1587
18 2 1.0 1.0 3.0 2190
19 0 1.0 1.0 3.0 1535
20 4 1.0 1.0 3.0 2758
21 2 0 1.0 3.0 2420
22 2 2.0 1.0 3.0 1545
23 2 1.0 0 3.0 2182
24 2 1.0 2.0 3.0 2233
25 2 1.0 1.0 0 2257
26 2 1.0 1.0 6.0 2667
27 2 1.0 1.0 3.0 Plus Zn 1965
28 2 1.0 1.0 3.0 Plus Fe 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.




59
3
CU
2
0

O
o IIII I I I I
.JO I 2 3 4 0.5 1.0 1.5 2.0
w
SOIL APPLIED LIME (t/ha) FOLIAR APPLIED Mn (kg /1000 I /ha)
z
< 3,n
z
w 0 No Cu
m
O-
0
I I I I I I I
O 0.5 1.0 1.5 2.0 1.5 3.0 4.5 5.0
SOIL APPLIED B (kg/ha) Mo SEED TREATMENT
(g/kg seed)
Figure 2.6:3. Soybean yields as affected by lime, Hn, B, Ho applications.
Yurimaguas, 1976.




60
cated that B content in the soils of the Yuri- boron was observed. As in the case of soybeans maguas Experimental Station is very low and described earlier, the biggest response was to the not measurable in most of the cases. first 0.5 kg B/ha. An additional response was obFor these reasons, it was necessary to deter- served with the last 0.5 kg B/ha increment. This mine the effect of five levels of Cu, Mn, B, and last yield increment is difficult to interpret. Mo on soybeans (cv. National) and peanuts A response to Mo applied to the seeds was
(cv. Blanco Tarapoto) growing simultaneously also observed. The results indicated that when on two different experiments. Both crops were 1.5 g Mo/kg of seeds were applied as a slurry, planted in a field adjacent to the one where yields of peanuts increased from 3.8 tons/ha to secondary and micronutrient studies were con- 4.5 tons/ha, with no further increments with adducted. Thus, the soil was acid (pH 4.2), had ditional Mo dosages. However, the high yield 2.3 me AI/100 g soil, and was low in N, P, and with the check (3.8 tons/ha) also indicated a K. A central composite rotatable design was good N fixation when Mo was not applied. A used on both experiments. Peanuts were planted survey of the roots of the peanuts showed that on August 3, 1976, and harvested on November nodulation in all plots was very good with most 18. Soybeans were planted also on August 3, of the nodules pink in color. 1976, but seedlings did not emerge well, due to Additional treatments showed that when low seed quality. A new planting was on none of the microelements (Cu, Mn, B, and Mo)
September 3 and was harvested at the time that was applied, peanuts yielded only 3.0 tons/ha this report was being written. Only results on (treatment 17). This was the same amount obpeanuts will be presented at this time. Treat- tained in the zero B plots. No peanut yield rements and nutrient levels applied are presented sponse to the application of 4 kg Zn/ha was in Table 2.6:4. noted. It will be remembered that corn also
Results. Results of peanut yields are pre- failed to respond to Zn applied to the same soil sented in Table 2.6:4. It can be observed that (1974 Annual Report). yields were generally over 4,000 kg/ha, which is From the last two microelement experiexcellent for the zone. As indicated in Table ments, it can be indicated that B, Mo, and Cu 2.6:4, no N was applied to the plots. The idea deficiencies can be expected in Yurimaguas was to test peanut response to Mo in the pre- Paleudults when they are continuously cropped. sence of only the native soil N. Yields were re- No response to Zn or Mn was found with soymarkably good, indicating that peanuts can be beans or peanuts. Initially reported low levels of grown with only the native soil N where the Mn in soybean leaves are thought to be related proper Rhizobia inoculum is used. Fig. 2.6:4 in- to other nutrient deficiencies. The question redicates that there was no response of peanuts to mains on how this response or lack of responses copper applied to the soil or to manganese ap- will change after plants use the native micronuplied to the leaves. However, a high response to trients in the soil. Thus, the need for long-term




61
Table 2.6:4. Peanut yields as affected by Cu, Mn, B, and Mo applications.
Amounts Applied
Peanut
Tmt. Cu Mn B Mo Remarks-/ Yield
kg/ha kg/1000 kg/ha g/kg kg/ha
1/ha seed
1 1 0.5 0.5 1.5 4707
2 3 0.5 0.5 4.5 4375
3 1 1.5 0.5 4.5 5208
4 3 1.5 0.5 1.5 4083
5 1 0.5 1.5 4.5 4041
6 3 0.5 1.5 1.5 4333
7 1 1.5 1.5 1.5 4833
8 3 1.5 1.5 4.5 3875
9 1 0.5 0.5 4.5 3625
10 3 0.5 0.5 1.5 4750
11 1 1.5 0.5 1.5 4916
12 3 1.5 0.5 4.5 4250
13 1 0.5 1.5 1.5 3875
14 3 0.5 1.5 4.5 3625
15 1 1.5 1.5 4.5 4541
16 3 1.5 1.5 1.5 4333
17 0 0 0 0 Check 3041
18 2 1.0 1.0 3.0 4381
19 0 1.0 1.0 3.0 4291
20 4 1.0 1.0 3.0 4416
21 2 0 1.0 3.0 4374
22 2 2.0 1.0 3.0 4458
23 2 1.0 0 3.0 3401
24 2 1.0 2.0 3.0 5291
25 2 1.0 1.0 0 3791
26 2 1.0 1.0 6.0 4458
27 2 1.0 1.0 3.0 Plus Zn 4124
28 2 1.0 1.0 3.0 Plus Fe 4042
.!A basal application of 2 tons lime/ha, 70 kg P/ha, 102 kg K/ha, and 30 kg Mg/ha was made. No N was applied.
-/Four kg Zn/ha and 1 kg Fe/lO00 1/ha were applied in each treatment.
Iron was sprayed together with Mn at 25, 36, and 50 days after
planting.




62
5
4
3
0
4- I I I I I* III
O I 2 3 4 0.5 1.0 1.5 2.0
(/) SOIL APPLIED Cu (kg/ha) FOLIAR APPLIED Mn
0
_J
UJ (kg /1000 I /ha)
D5

3
0 0.5 1.0 1.5 20 1.5 3.0 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.




63
micronutrient studies is evident. The data indi- No nitrogen was applied since, from previous cate that in order to continue obtaining good experience, the ash should supply enough N for yields in the continuous cropping experiments, the first crop. Succeeding crops were legumes or the next micronutrients should be applied in the non-nitrogen responsive crops (Fig. 2.7:1). Magfollowing amounts per crop: 0.5 kg B/ha (as nesium was applied since it has been shown Borax), 1.5 g Mo/kg seed (as ammonium molyb- (Annual Report 1975) that Mg deficiency was date), and 1 kg Cu/ha (as copper sulfate). probably one of the main reasons for the declining yields in the rotation experiment of Chacras
2.7 INTEGRATED CROPPING SYSTEMS 1, 2, and 3. Micronutrients were applied as insurD. E. Bandy ance since it was still not known for sure if one
In December 1976 an experiment was ini- year of cropping will use up all the micronutiated in a new chacra (Chacra 5) that was re- trients from the ash. It has been shown in cently prepared for planting by the traditional Annual Reports 1974-1975 that micronutrient slash-and-burn method. The experiment is de- deficiencies of Mo and possibly Cu have apsigned to confirm or integrate results that have peared after an area has been intensively been previously shown at the station. cropped for two to three years.
The experiment used low levels of fertilizer Lime was necessary to apply since these and lime since previous Annual Reports (1973 Ultisols of the Yurimaguas soil series, are too and 1974) have documented well that newly acidic and too Al saturated (Annual Report
cleared land has only enough nutrients in the 1973) for most crops to produce any reasonable ash from the burn to produce fairly decent yield unless the exchangeable Al has been neuyields for one or two crops, but not enough for tralized to a minimum of 30-40% Al saturation, a whole year of intensive cropping. With the depending on crop tolerance to Al. proper selection of crop species and agronomic Preliminary results showed no negative efpractices it is possible to grow three crops a year fects of the low fertilizer and lime rates for rice, with very low levels of technical inputs and still cowpeas, soybeans, peanuts, sugar cane or gain respectable yields. The Annual Reports of cassava. Corn did show nitrogen deficiency 1974 and 1975 have shown that a certain type symptoms. Complete yield data will be reported of intercropping, i.e., relay cropping, is best in the 1977-1978 Annual Report. suited for this area. Fertilizer rates were NPK at
0-35-66 kg/ha, Mg at 18 kg/ha, and the micronutrients 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.




CLEARING # 5 CROP 1976 1977 1978 -SYSTEM Dec. Jan. Feb. Mar. April .May June July Aug Sept. Oct. Nov. Dec. Jan. Feb.
RICE
C ASS AVA IKUDZU
PEANUT
2 CORN
P ASSAVA KUDZU
3 1 SOYBEAN
I PEANUT I
CASSAVA IKUDZU
4 SUGAR CANE I KUDZU
I COWPEA I COWPEA I
Figure 2.7:1. Schematic diagram of the integrated cropping experiment with low inputs begun in December, 1976.




65
Aerial view of small farms in area surrounding Yurimaguas, Peru.
Rice, peanut and corn fertilization study at the Yurimaguas Agricultural Experiment Station.







67
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. Unal, Minas Gerais. March, 1977.




68
This report covers agronomic research con- 3.1 CROP WEATHER
ducted cooperatively by scientists from Brazil's W. Espinosa and M. Jarreta Junior Centro de Pesquisa Agropecuaria dos Cerrados Meterological data for the 1975-1976 (CPAC), Cornell and North Carolina State agricultural year at CPAC are given in Table
Universities. It includes field work conducted 3.1:1. Average values for 35 years at nearby from October 1975 through September 1976, Formosa are presented in Table 3.1:2.
encompassing a full agricultural year with the The temperature the morning of July 7, 1975-1976 rainy season and the 1976 dry 1975, at CPAC was unusually low (40C) as a
season. Research conducted independently of consequence of a cold wave which covered the seasons is also reported. southern part of Brazil, causing great agriculThis report will center on studies which tural losses, particularly in the state of Parana. evaluated effects on crops of residual lime, Ca Precipitation during this year (1243 mm) and Mg downward movement, residual P, was considerably lower than the average of
residual Zn, K and Mg fertilization, and N fer- 1580 mm, due to reduced rainfall in the tilization. Also discussed are crop species and months of December, January, March and varietal tolerances to Al toxicity and low April. Four dry spells (veranicos) occurred as available P, effects of P, lime and Si on soil shown in Fig. 3.1:1. properties and plant growth, and an outreach Fig. 3.1:2 shows the 1975-1976 meteorostudy of Cerrado soil properties. logical water balance for CPAC using Class A
Unless otherwise specified, all field experi- pan evaporation. For comparison, the water ments were conducted on a clayey Dark Red balance based on solar radiation calculated
Latosol (Typic Haplustox, fine, kaolinitic, according to Hargreaves method and using isohyperthermic) located on a second erosion 35 years of data collected at Formosa is presurface at CPAC near Brasilia. Properties of sented in Fig. 3.1:3. this soil were described in previous Annual
Reports and are typical of acid Oxisols of 3.2 RESIDUAL LIME EFFECTS tropical savannas. Generally speaking, these A. RESIDUAL EFFECTS OF LIME ON soils are well-drained, relatively deep, acid, low THE CLAYEY DARK RED LATOSOL in organic matter, P, K, Ca, Mg, with a rela- E. Gonzalez, E. Lobato and W. Soares tively high P retention capacity. These Oxisols The effect of liming acid soils is usually are not as susceptible to soil compaction as are expected to last for several years. It is also the sandier Ultisols of the Amazon Jungle. expected that this effect will be shorter in the




69
Table 3.1:1. Meteorological data for the agricultural year 1975/1976,CPAC,
(150 36'S, 470 42'W, altitude 1010 meters).
Temperature (C)
Precip- Evapor- Relative Solar
Month Max. Min. Avg. itation ation Wind Humidity Radiation
(mm) (mm) (m/s) (%) (cal/cm 2/day)
July 23.7 12.5 18.4 8.2 170.5 1.3 66.5 412.9
August 27.2 14.8 21.0 0 213.6 1.1 56.0 480.7
September 28.5 16.6 22.6 3.0 242.2 1.1 55.5 -October 28.3 17.3 22.8 104.3 169.9 0.8 58.4 416.3
November 26.4 17.6 22.0 254.3 141.2 0.8 64.7 421.6
December 27.0 16.8 21.9 156.3 166.5 0.6 60.2 468.0
January 27.8 16.7 22.2 146.9 167.8 -- 59.2 484.0
February 26.6 17.8 22.2 311.8 132.7 0.8 63.1 419.4
March 27.4 17.7 22.6 186.2 146.3 0.8 61.3 -April 27.9 16.9 22.4 12.2 155.8 0.9 57.2 -May 26.7 15.3 21.0 59.4 134.6 0.7 58.7 -June 26.7 13.6 20.1 0 166.9 0.8 51.0 -Source: Relatorio Tenico Anual, CPAC, 1976, Brasilia D. F.




Table 3.1:2. Average of 35 years of meteorological data for Formosa, GO (150 32'S, 470 18'W, altitude 912 m).
Maximum
Average precipiAtmos- monthly tation
pheric Avg. Min. Max. Relative precipi- in 24
Month pressure Temp. Temp. Temp. Humidity Cloudiness tation hours Evaporation Insolation
(mm) (C) (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 Te~nico Anual, CPAC, 1976. Brasilia D.F.




71
60
Drought
40
20
E E
" 5 15 25 5 1 25 25
z Oct. 1975 I Nov.- I Dec. 1975-I
z
SDrought Droughl Drought
1- -I -* I-- 40
20
5 15 25 5 15 25 5 15 25
I Jan. 1976 I Feb. 1976 Mar. 1976---I
Figure 3.1:1. Daily rainfall at CPAC during the wet season 1975-1976.




72
30- 0-0 Rainfall -600
0- s Evaporation (Class A
pan)
0-0 Temperature
20j"40
(3
0
10 200
DEFICIT DF
Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May June
Figure 3.1:2. Meteorological water balance for agricultural year 1975-1976 for CPAC based on class A pan evaporation.
H Rainfall
30 o~--o Evaporation60
o>-o Temperature
,- 0 340
10 O -E 200
, DEFICITr MFI
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).




73
tropical region than in the temperate region be- made before the residual study was established. cause of more intensive climatic conditions of Tops were removed from the fields at each harhigh rainfall and high temperature. In the vest. Grain yields of two varieties of soybeans
humid tropical areas, leaching of basic cations planted on these 3-year old plots are presented becomes important because it not only reduces in Table 3.2:1. As with the Stylosanthes, there the residual effect of lime but affects the depth was a significant increase in yields of both varibelow the zone of lime incorporation. This is eties with the first increment of lime. With particularly important where subsoil acidity is rates greater than 1 ton there were further ina problem for root development, creases in yields, but this benefit was only
The first part of this discussion deals with a significant at the 6 ton level with the Viqosa soybean experiment conducted at the station variety. The other variety, IAC-2, did not reto test the residual effect of various lime levels. spond as well at the highest level of lime. OverThe second part treats the movement and im- all, yields obtained in this study may be conplications of base movement in the profile sidered somewhat low for experimental condifrom plots limed & fertilized in different years. tions. Both varieties showed an impressive vegeSoybean Growth Under Various Residual tative and reproductive growth at all levels of
Levels of Lime lime. Grain yields, however, were not as markThis residual study of lime was conducted edly increased because of a long rainy period in the wet season 1973-1974 on an acid soil which delayed harvest and reduced yields by
where lime had been applied in November damaging some of the pods.
1970 and Stylosanthes was planted during that There are important features of the effect
time. Soil samples taken before the application of the various residual lime levels on soybean of lime indicated that the soil was very acid yields. The increase in yields obtained with the (pH around 4.6) with a high Al saturation in first increment of l ime was considerable, in the the topsoil and subsoil (80 to 90 percent). The order of 800 kg/ha for both varieties. The inamount of exchangeable Al was around 1.5 teresting point is that this increase occurred
me/iQO cc with the exchangeable Ca + Mg when the soil was still very acid (Table 3.2:2).
around 0.2 me/iQO in the top 30 cm of soil. The second soil sampling which was made after
Different levels of calcitic limestone were in- the harvest of the soybean crop showed that Al corporated to a depth of about 20 cm. These saturation was around 50 percent at the 0-15
levels of lime were effective in increasing Stylo- cm depth and 63 percent at the 15-30 cm. This santhes growth. The highest dry matter produc- indicated that these two varieties were relation was obtained with 4, 6, and 8 tons of lime tively tolerant to Al and responded well to [no statistical lime (1 ton)]I Two harvests were small additionsof lime.




74
Table 3.2:1. Residual effect of various levels of
lime on grain yields (14% moisture) of two soybean varieties in the LE
soil.
Previous Variety
Lime rates Vigosa IAC-2
ton/ha kg/ha------0 1095 1059
1 1902 1868
2 2137 1919
4 2139 2294
6 2695 2405
8 2729 2259
LSD Lime = 545
. 05
LSD.5 Var. = 467
1Values are mean of 4 replications.




75
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 application. The second one in March 1974, after harvesting
the soybean.
Exchangeable
Lime Depth of
Levels Sampling pH Al Ca+Mg Al satur.
ton/ha cm ---me/lOOcc --First Sampling
0 0-20 4.2 1.76 0.32 85
20-40 4.1 1.37 0.27 84
1 0-20 4.5 1.22 0.77 61
20-40 4.3 1.32 0.29 82
2 0-20 4.5 1.22 0.95 56
20-40 4.4 1.25 0.37 77
4 0-20 4.7 0.82 1.57 34
20-40 4.4 1.17 0.37 76
6 0-20 5.1 0.32 2.85 12
20-40 4.7 1.10 0.63 64
8 0-20 5.3 0.10 3.60 3
20-40 4.6 1.05 0.72 59
Second Sampling
0 0-15 4.7 1.34 0.57 70
15-30 4.8 1.32 0.51 72
1 0-15 4.8 1.25 1.29 49
15-30 4.8 1.23 0.73 63
2 0-15 5.0 0.95 2.36 29
15-30 4.8 1.12 1.00 53
4 0-15 5.1 0.56 2.23 20
15-30 4.9 0.92 0.99 48
6 0-15 5.4 0.21 2.91 7
15-30 5.1 0.52 1.91 21
8 0-15 5.6 0.15 3.70 4
15-30 5.1 0.51 1.90 36




76
Another important aspect is that a further quate. Nitrogen concentration was increased response was obtained with the 6 tons of lime with the higher lime rates suggesting that noduafter a plateau was reached at the 2 and 4 lation was more effective when soil acidity was
ton/ha level. The Al saturation at the 6 ton reduced further.
level was less than 10 percent in the 0-15 cm After three years of cropping there was a
depth and around 20 percent in the 15-30 cm. considerable residual effect of liming in this
This is more in agreement with the results of soil. Soil analysis showed that most of the Al Soares et al., in 1974 on two Dark Red Lato- was still neutralized at the end of three years
sols where soybean yields increased sharply where 6 tons of lime/ha were initially applied.
with 5 tons/ha of lime, which had reduced Al Results of the first sampling suggested that
saturation to 10 percent. They, however, did lime was still reacting with the soil one month
not have any rates less than 5 tons/ha. Spain after application. et al., also in 1974 found that soybeans respon- Even though 1 ton of lime increased yields
ded to lime applications up to 6 tons/ha on an considerably, it still was not sufficient for maxacid Colombian Oxisol, but most of the re- imum growth and for efficient nitrogen utilizasponse occurred with an application of 2 tion. It was necessary to reduce Al saturation
tons/ha. The Vigosa and IAC-2 varieties yielded to less than 10 percent to obtain the highest an additional 800 and 550 kg/ha, respectively, yields in this experiment. This corresponded to as lime rates were increased from 1 to 6 a soil pH of about 5.4 and is also the pH at
tons/ha. There was no further increase at the which Al was reduced to minimal levels in the
8 ton level and with the IAC-2 there was a LE soil.
slight reduction in yield. This increase in yields Cation Movement from Limed Plots with the 6 ton/ha rate represented a response Natural downward movement of Ca and Mg
to a diminished Al saturation (about 10 per- was studied on certain plots of the Dark Red
cent) or may have been due to greater availa- Latosol. These plots had been limed with calbility of Mo. No Mo was applied with the soy- citic limestone in different years and received beans, and the only Mo that had been applied different fertilization practices. Results from
previously was before planting the Stylosan- the oldest limed plots sampled for this particthes. Nutrient concentration of the trifoliates ular study are reported in Table 3.2:4. This was of the two varieties (Table 3.2:3) showed Ca to an experiment established in 1967, with Stylobe in the sufficiency range of 0.36-2.00 percent santhes under different rates of lime and P. The even in the check treatment. The concentration lowest level of P (33 kg/ha as triple superphosof Ca increased with increasing levels of lime phate) applied in that year with no additional P but all were within the above range. The con- in subsequent years was selected in order to centration of Mg may also be considered ade- avoid other sources of Ca besides the lime




77
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 ------------ % ------------ --Jg/cc--0 Vigosa 3.77 .19 1.9 .67 .27 121 177
1 Vigosa 4.04 .20 1.9 .95 .27 87 116
2 Vigosa 3.93 .19 1.7 1.01 .27 76 95
4 Vigosa 4.39 .21 1.8 1.17 .32 71 94
6 Vigosa 4.19 .21 1.7 1.19 .28 70 96
8 Vigosa 4.46 .21 1.6 1.27 .29 57 87
0 IAC-2 3.79 .19 1.9 .59 .23 134 178
1 IAC-2 3.83 .19 1.9 .63 .24 103 133
2 IAC-2 3.31 .16 1.8 .89 .24 95 124
4 IAC-2 4.00 .20 1.8 1.19 .30 93 87
6 IAC-2 4.22 .20 1.7 1.28 .28 66 57
8 IAC-2 4.04 .21 1.8 1.42 .32 75 88




78
Table 3.2:4. Soil analysis of limed plots (1967) in the LE soil
that were planted to Stylosanthes. Sampl s 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 cm --- me/lOOcc --- %
0 0.0- 7.5 4.67 1.04 0.25 0.05 78
7.5-15.0 4.60 1.18 0.24 0.05 79
15.0-22.5 4.80 1.12 0.25 0.05 79
22.5-30.0 4.80 0.96 0.25 0.05 78
30.0-37.5 4.90 0.81 0.28 0.03 72
37.5-45.0 5.00 0.61 0.29 0.02 66
45.0-52.5 5.00 0.51 0.25 0.03 63
52.5-60.0 5.10 0.44 0.25 0.03 61
60.0-67.5 5.10 0.45 0.30 0.03 56
67.5-75.0 5.10 0.46 0.35 0.03 55
5 0.0- 7.5 6.20 0.06 5.98 0.17 1
7.5-15.0 5.45 0.33 2.50 0.07 11
15.0-22.5 4.90 0.86 0.65 0.05 55
22.5-30.0 4.90 0.84 0.35 0.04 68
30.0-37.5 4.93 0.88 0.25 0.04 75
37.5-45.0 4.95 0.72 0.25 0.04 71
45.0-52.5 4.97 0.59 0.28 0.02 66
52.5-60.0 4.95 0.57 0.25 0.02 68
60.0-67.5 5.10 0.50 0.30 0.02 61
67.5-75.0 5.10 0.28 0.25 0.03 50
10 0.0- 7.5 6.45 0.05 6.32 0.21 1
7.5-15.0 6.65 0.04 5.91 0.15 1
15.0-22.5 5.70 0.04 3.88 0.07 1
22.5-30.0 5.06 0.57 0.72 0.05 43
30.0-37.5 5.04 0.56 0.53 0.03 50
37.5-45.0 5.07 0.47 0.47 0.03 48
45.0-52.5 5.09 0.51 0.38 0.03 55
52.5-60.0 5.10 0.39 0.38 0.03 48
60.0-67.5 5.10 0.51 0.45 0.03 51
67.5-75.0 5.10 0.31 0.40 0.02 43
1Values are mean of 2 plots. Each plot sample was a composite of
3 subsamples.




79
material. Thus, it is estimated that lime was the marked downward movement of Ca to about only source of Ca since the triple superphos- 15 cm below the depth of incorporations phate would have provided very little but a (Table 3.2:5). This caused the decrease of Al uniform basal amount of Ca to the soil. The saturation in the 30-45 cm zone from 70-75% only source of Mg was 200 kg MgSO4/ha also initially to about 50% or less within 11/2 years applied in 1967 with no further application in after liming. later years. Since no MgSO4 was applied, there was little
Not much movement of cations occurred Mg in the profile. The Mg in the top cm came
below the zone of lime incorporation with the mostly from the calcitic limestone. This was the 5 ton level. It is assumed that lime was not same material as that applied in the depth of physically incorporated below 15 cm depth. A liming experiment. small rotovator was used to incorporate this lime In the Zn I I experiment, several anions were and good mixing with the soil was accomplished, incorporated along with the limestone. These Some Ca seems to have moved into the 15.0- included chlorides (from KCI), nitrates (from 22.5 cm depth, but insignificant amounts of Ca nitrification of NH3 of the urea) and some sulmoved below 22.5 cm. With the 10 ton level a fate (from ZnSO4). These anions may have enconsiderable amount of Ca moved into the hanced Ca movement acting as the accompany15.0-22.5 cm, a much lower quantity moved ing ion in the leaching process. Work in South below that zone into the 22.5-45.0 cm depth, Africa by Reeve and Sumner in 1972 reported and insignificant amounts below 45.0 cm. For that heavy fertilization and high rates of lime all practical purposes, the effective depth of increased the rate of cation movement, but the movement was limited to 22.5 cm where most Ca had little effect on exchangeable Ca and Al of the Al was neutralized. Below that depth, Al below a depth of 45 cm in a typical Natal Oxisol saturation was still high, being around 50 per- after 14 years. Dolomitic limestone was applied cent, which may be toxic for many crops. The in the top 15 cm. data also showed that essentially all the Mg In the Stylosanthes study there was no source applied as MgSO4 was lost, most probably by of anions as in the Zn 11 experiment, and very plant uptake (there were 6 cuttings of the little Ca actually moved from the zone of appliStylosanthes). Only a small portion was retained cation. Besides the need of anions for cation in the limed zone by pH-dependent charges. movement in the soil, a high rate of lime is also In a more recent experiment (Zn 11 experi- important. The literature on this subject indiment) where high rates of lime were incor- cates that movement occurred only at high rates porated to about 20-25 cm in November 1972 of lime, and this rate has been related to the and the soil sampled in April 1974, there was texture of the soil.




80
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.
ton/ha cm --me/lOOcc--%
24 0.0- 7.5 7.68 tr. 8.13 0.12 0
7.5-15.0 7.65 tr. 7.45 0.08 0
15.0-22.5 7.44 tr. 6.88 0.07 0
22.5-30.0 5.62 0.06 4.38 0.07 1
30.0-37.5 4.98 0.62 1.38 0.05 44
37.5-45.0 4.83 0.67 0.59 0.02 53
45.0-52.5 4.73 0.63 0.38 0.03 63
52.5-60.0 4.54 0.65 0.35 0.04 63
60.0-67.5 4.46 0.63 0.30 0.04 65
67.5-75.0 4.41 0.65 0.25 0.03 70
16 0.0- 7.5 7.02 tr. 6.95 0.13 0
7.5-15.0 7.35 tr. 7.50 0.13 0
15.0-22.5 7.15 tr. 7.25 0.08 0
22.5-30.0 6.12 tr. 3.70 0.07 0
30.0-37.5 5.07 0.67 1.21 0.03 35
37.5-45.0 4.97 0.68 0.76 0.03 46
45.0-52.5 4.80 0.63 0.45 0.03 57
52.5-60.0 4.75 0.61 0.43 0.02 58
60.0-67.5 4.52 0.63 0.35 0.03 63
67.5-75.0 4.50 0.90 0.30 0.03 73
8 0.0- 7.5 7.15 tr. 6.02 0.18 0
7.5-15.0 7.30 tr. 6.13 0.14 0
15.0-22.5 7.35 tr. 6.35 0.10 0
22.5-30.0 6.60 tr. 4.73 0.08 0
30.0-37.5 5.10 0.64 1.09 0.07 36
37.5-45.0 5.10 0.67 0.94 0.04 41
45.0-52.5 4.75 0.70 0.39 0.03 62
52.5-60.0 4.60 0.74 0.30 0.02 70
60.0-67.5 4.55 0.76 0.30 0.03 70
67.5-75.0 4.35 0.74 0.25 0.02 73
1Values are mean of 3 replications at each lime level. Each replication is a composite of 4 subsamples.




81
B. RESIDUAL EFFECTS OF LIME RATE either depth. The yields from rates of 2 and
AND INCORPORATION DEPTHS 4 tons/ha at either depth were not significantly
J. G. Salinas, E. Gonzalez, E. J. Kamprath and different from the same depth at 1 ton/ha. P. A. Sanchez At 8 tons/ha, however, both depths of this lime
A fifth crop of corn was grown during the rate yielded significantly more than all lower 1975-1976 rainy season in order to continue rates. This yield increase could be explained by evaluating the residual effects of lime applica- the very low Al saturation maintained over time tions and changes in soil properties. The experi- on the surface and subsurface. On the other mental design and methodology has been hand, the non-significant difference between reported in previous annual reports. Besides shallow and deep application at this highest rate the evaluation of annual, cumulative and essentially was due to the fact that in the subresidual effects of liming on the grain produc- surface (15-30 cm) at the shallow application, tion as well as its effects on the soil properties the Al saturation was quite low (less than 20% to the depth of lime incorporation, a decision Al saturation) which indicated no toxic effect was made to study the soil properties in terms on root growth. of downward movement of basic cations and Effects on Soil Properties root development as deep root proliferation. The Table 3.2:6 shows the change in soil pH, The N, P and K applications continued this exchangeable Al and percent Al saturation in sea so n with a broadcast application o f samples taken after each crop harvest from May 124 kg K/ha as KCI, a banded application of 1973 to April 1976. Soil pH at two depths for 44 kg P/ha as triple superphosphate (TSP) and all lime rates after each of five crops is shown in 20 kg N /ha as urea followed by three side- Fig. 3.2:2. In general, the pH gradually dedressed applications totaling 200 kg N/ha as creased in both shallow and deep incorporations. urea. As in earlier experiments, the same corn With time the pH values for both shallow and variety Cargill-1 11 was planted in 80 cm rows deep placement of 1, 2 and 4 tons lime/ha deat an approximate population of 50,000 creased to similar values. Although there was a plants/ha. The experiment was planted on decline in pH at the rate of 8 tons/ha incorOctober 31, 1975, and harvested on porated to 30 cm depth, this high rate of lime March 20, 1976. still maintained substantial residual effect after Yields five years. In addition, the pH values at
Results of the fifth corn crop are shown 15-30 cm depth in shallow treatments showed in Fig. 3.2:1. As in previous crops, significant increases with time even though no lime was yield increases were produced by the residual applied at this depth. effect of only 1 ton lime/ha incorporated to




82
6
(0-30 cm)
a 5 -0-15cm)
C
0
) 4
a
-J
w
5:
z S3
SLSD05= 0.67 tons / ha
0 I 2 4 8
LIME APPLIED IN 1972 (tons/ha)
Figure 3.2:1. Corn yields of the fifth crop (1976) as
affected by lime applied in 1972. Brasilia.




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 H 2 0--------------------- me/lO0cc ------------------------%------------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 1.03 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 oo
WA
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




84
Shallow Placement Deep Placement
(0-15 cm) (0-30 cm)
7 0-15 cm Soil Depth 0-15 cm Soil Depth
lime rate lime rate
(tons/ha) (tons/ha)
6 "1
88
5 4 4
22
0
4
i-I I I I Ii I I I I I
1 0 1 2 3 4 5 1 2 3 4 5
C. (1973) (1976) (1973) (1976)
-J
S6 -15-30cm Soil Depth 15-30cm Soil Depth
8
5- 8
: 4 4
S2 2
4- 0
0 2 3 4 5 1 2 3 4 5
(1973) (1976) (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, 19721976.




85
Perhaps a better picture of these differences From observation of the cumulative yields, one is given by consideration of change of percent Al notes equal yields from one-half as much lime saturation. Fig. 3.2:3 shows a progressive de- when incorporated to 30 cm as compared with crease in percent Al saturation in the 15-30 cm incorporation to 15 cm. layer of shallow applications which was asso- The residual effects of the original lime treatciated with downward movement of basic ments applied in 1972 are shown in Fig. 3.2:4.
cations. Thus, five years after lime applications These effects are expressed as percent of maxin the Dark Red Latosol, the additional benefit imum yield relative to the highest absolute of deep incorporation of lime which was ob- yield which was always produced by 8 tons/ha
tained during the first three crops started to of lime incorporated to 30 cm. After five years, decrease in the fourth crop and was almost 1, 2 and 4 tons/ha lime at shallow and deep
negligible after the fifth crop. However, from incorporations produced similar yields. the economical point of view, the superior However, the lack of differences between
performance of deep application is still evident shallow and deep placement might be atttribusince deep lime placement produced the same table, in part, to the lack of natural drought
yield with half the rate of lime as did shallow period in this wet season. The shallow incorporaapplication. It is important to remark that the tion of 8 tons lime/ha produced 90% of the fifth crop was planted on the date in which the maximum yield and its residual effect was still probability was high to escape from a severe considerable. This experiment will be continued "'veranico" during the grain formation stage. by CPAC staff members in order to fully evalIn addition, a severe veranico did not occur uate the residual effects. during this wet season. The only slight drought Yields of the five crops expressed as percent period within the 1975-1976 rainy season of the maximum yield (8 tons lime/ha incoroccurred for 8 days at the beginning of January porated to 30 cm) as a function of the soil pH 1976, 65 days after planting this experiment and are given in Fig. 3.2:5. In general, after each which did not cause serious plant water stress crop the curves representing shallow and deep due to cloudiness and high humidity. applications shifted to the left indicating a deCumulative and Residual Effects of Liming crease of pH values at all lime rates. Thus, the
The seasonal and cumulative yields of the residual effect of lime diminished with cropping. five crops are presented in Table 3.2:7. Significant differences occurred between shallow
Although there was no difference between and deep incorporations of lime with the first
shallow and deep applications in the fifth crop, three crops in which the differences in pH values the overall trend still showed that deep lime at 15-30 cm soil layers were large. With time, application had a positive effect after five years. these differences became smaller and practically




86
Shallow Incorporation Deep Incorporation
80 0-15cm Soil Depth O-15cm Soil Depth
0
60 I
I/
40
2 2
2
20 -
z 4
0
4
< O 8
80 -15-30cm il Depth .15-30cm Soil Depth
2 O 0cjm
D0
z 60
40 2 2
4
20- 4
8
0 n hI ~-r- 8
I 2 3 4 5 I 2 3 4 5
CROP SEQUENCE
Figure 3.2:3. Residual effects of lime rates and depth incorporation on the Al saturation after five crops.
Brasilia, 1972-1976.




87
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 Cumuof 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
LSD05 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.




88
Shallow Placement (0-15cm) Deep Placement (O-30cm)
(Maximum Yields, tons/ha) (4.8) (6.7) (3.6) (7.1) (O) 100 lime rate 6
0 (~t /ha)
-j 8
80 4 2
2 2
X
0
40
z
U 20
IrI
a.0
-O~ I I I I I I I I I I
1 2 3 4 5 I 2 3 4 5
1972 1973 1974 1975 1976 1972 1973 1974 1975 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.




89
Soil Depth 0-15cm Soil Depth 15-30 cm
D: Deep Placement (0-30cm)
S: Shallow Placement (0-15cm)
100 b
S S
60- -lt Crop
20 ,.
100 DS D
j 60 2d Crop
w
20
20 ,
S o00o- D D
d
X 60- S 3- Crop
, 60 --4 Co
L 20 ,
0 100 DS -,
ZS S
W 60- 4 Croc
0- 20 I I I
100 D D
/ th
60[/ 5- Crop
201 1 I
4.5 5.5 6.5 4.5 5.5 6.5
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.




90
disappeared in the fourth and fifth crops. The to a 90 cm depth. Changes in pH, exchangeable main reasons seemed to be a result of the de- Al, Ca, Mg and percent Al saturation are shown crease in the residual effect of lime incorporated in Figs. 3.2:7-3.2:10. The results indicated to a 30 cm depth and the decrease in Al satura- clearly that a factor other than simple pH effect tion in the shallow lime treatments at the was involved. As lime rates were increased,
15-30 cm depth due to a downward movement notable differences in pH values at least until
of Ca and Mg into this soil depth. 45 cm depth were noted. The greatest difference
Root Depth and Downward Movement of was found between 0 and 8 tons/ha shallow and
Basic Cations deep incorporation. The data strongly indicate
Eighty days after planting, three pits were that after five years substantial Ca and Mg have dug and opened to 100 cm in plots which moved through the profile to depths of 45
received no lime and 4 tons lime/ha shallow and to 50 cm. deep incorporation, respectively. As expected, Proportional to the lime rate, Ca and Mg condepth and proliferation of roots increased with centrations increased and Al saturation deincreasing depth of liming (Fig. 3.2:6). Where creased through the profile. Considering 50% Al no l ime was applIied most of the roots were con- saturation as a critical value for adequate corn centrated close to the row and just in the growth, the results showed that five years after
0-15 cm soil layer. This type of rooting distribu- shallow applications at the rates of 2 and tion could be related to the banded P applica- 4 tons/ha this critical Al saturation value is tion. At 4 tons lime/ha shallow application a found at 30 cm deep. With deep placement high concentration of roots still were observed (0-30 cm) of 2 tons/ha the critical value is found in the 15 cm soil layer but their distribution around 35 cm deep and for 4 tons/ha near covered all this layer, with some of them having 45 cm deep. With the highest lime rate passed 20-30 cm below the level to which lime (8 tons/ha) it is interesting to observe that 50% had been incorporated. Deep liming resulted in Al saturation was encountered somewhere bea fairly uniform rooting distribution in the tween 50 and 70 cm deep under both shallow 0-15 cm soil layer with considerable roots and deep incorporation. In addition, at these
irregularly distributed to a 50 cm depth. This highest rates of lime incorporated at 0-15 and differential distribution of roots emphasized 0-30 cm the neutralization of aluminum in the the necessity for a more detailed soil sampling sublayers was quite similar. Small differences to deeper layers in order to evaluate the effects were observed with exchangeable Al and Ca + on soil properties of lime rates and depth of Mg under both shallow and deep placement at incorporation. After harvest of the fifth corn the highest lime rates. All these results are showcrop, soil samples were taken in several layers ing the benefit of movement of basic cations




91
100
20
Figure 3.2:6a. Corn root distribution as a function of depth in the zero lime treatment of the experiment on lime rates and depth of incorporation. Concentrated root zones correspond to regions of banded P applications. Fifth crop. Brasilia, 1976.




92
LIME EXP
4 TON/HA
hrLLW i
Yn
Figure 3.2:6b. Corn root distribution asa function of depth in the residual 4 ton/ha lime treatment with shallow (0-15 cm) incorporation. Fifth crop after liming. Brasilia, 1976.




93
LIME EXP
4 TON/HR
Figure 3.2:6c. Corn root distribution with depth in the residual 4 ton/ha lime treatment with deep (0-30 cm) incorporation. Fifth crop after liming. Brasilia, 1976.




I. SOIL pH-1
3 4 5 6 3 4 5 6
0 "' 1 0 / I I I,
lime rate-0 I 24 8 lime rate-O I 2 4 8
(tons/ha) (tons/ha)
15- 15
E
30- 30
- 45- 45
w
io
_J
60- 60
0
O)
75- 75
9 -SHALLOW PLACEMENT (O-15cm) 90 -DEEP PLACEMENT (O-30cm)
Figure 3.2:7. Residual effects of lime applications on soil pH after six crops; four corn and two sorghum crops. Brasilia, 1975-1976.