Citation
Tropical soils research program, annual report

Material Information

Title:
Tropical soils research program, annual report
Cover title:
Agronomic-economic research on tropical soils, annual report
Spine title:
Research on tropical soils
Creator:
North Carolina State University -- Soil Science Dept
Place of Publication:
Raleigh
Publisher:
Soil Science Dept., North Carolina State University.
Creation Date:
1975
Frequency:
annual
regular
Language:
English
Physical Description:
1 v. : ill. ; 28 cm.

Subjects

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

Notes

Dates or Sequential Designation:
5th, 1975.

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University of Florida
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University of Florida
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The University of Florida George A. Smathers Libraries respect the intellectual property rights of others and do not claim any copyright interest in this item. This item may be protected by copyright but is made available here under a claim of fair use (17 U.S.C. §107) for non-profit research and educational purposes. Users of this work have responsibility for determining copyright status prior to reusing, publishing or reproducing this item for purposes other than what is allowed by fair use or other copyright exemptions. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder. The Smathers Libraries would like to learn more about this item and invite individuals or organizations to contact Digital Services (UFDC@uflib.ufl.edu) with any additional information they can provide.
Resource Identifier:
000436827 ( ALEPH )
04039139 ( OCLC )
ACJ6840 ( NOTIS )
78643724 //r79 ( LCCN )
0161-8857 ( ISSN )

Related Items

Preceded by:
Agronomic-economic research on tropical soils, annual report
Succeeded by:
Research program on soils of the tropics, annual report for ...

Full Text
AGRONOMIC- ECONOMIC RESEARCH
ON TROPICAL SOILS
Annual Report for 1975
Soil Science Department
North Carolina State University
Raleigh, N.C.
under
Contract AID/ta-C-1236
with the
U.S. Agency for International Development







TROPICAL SOILS RESEARCH PROGRAM
ANNUAL REPORT FOR 1975
Soil Science Department
North Carolina State University Raleigh, North Carolina 27607
supported by
Contract A I10/ta-C-i 1236
with the
U. S. Agency for International Development
November, 1976







PERSONNEL
Administration Central America
Charles B. McCants, Department Head Robert E. McCollum, Project Leader
Pedro A. Sanchez, Program Coordinator Donald D. Oelsligle2, Assistant Professor
Bertha I. Monar, Administrative Secretary John J. Nicholaides, Assistant Professor
Dawn M. Silsbee, Bilingual Secretary Clifton K. Hiebsch, Research Assistant
Cathy L. Langley, Research Technician Alvaro Cordero V., Research Assistant
David Anderson, Research Assistant
Cerrado of Brazil
K. Dale Ritchey, Project Leader (Cornell)1 Extrapolation Studies George C. Naderman, Jr., Assistant Professor Stanley W. Buol, Professor of Soil Genesis Eugene J. Kamprath, Professor Robert B. Cate, Jr., Associate Professor
Enrique Gonzalez E., Research Assistant Arthur J. Coutu, Professor of Economics
Russell S. Yost, Research Assistant Walter Couto, Research Associate
Jos6 G. Salinas, Research Assistant Robert A. Pope, Research Assistant
Dale E. Bandy1, Research Assistant Raymond B. Daniels, Professor (USDA)
T. Jot Smyth, Research Assistant Richard K. Perrin3, Assoc. Prof. (Economics)
Alfredo S. Lopes, Research Assistant Leonidas Meji'a2, Research Assistant
Fred R. Cox, Professor Igo F. Lepsch2, Research Assistant
Jerry M. Bigham, Research Assistant
Amazon Jungle J. Ram6n Paredes2, Research Assistant
Pedro A. Sanchez, Project Leader Richard Schargel, Research Assistant
J. Hugo Villachica, Research Assistant Sahle M. Sertsu, Research Assistant
S. W. Buol, Professor Michael A. Granger2, Research Associate
D. Keith Cassel, Associate Professor
Gordon S. Miner, Assistant Professor
Cesar E. Lopez, Research Assistant
Christopher E. Seubert2, Research Assistant Edward J. Tyler2, Research Assistant
Michael K. Wade, Research Assistant
1Cornell University staff members working on cooperative project. 2Left during the year.
30n leave of absence at CIMMYT.







CONTENTS
Page
INTRODUCTION
Highlights of the year ................................................ 3
Collaborating institutions and individuals ................................... 7
JOINT NCSU-CORNELL RESEARCH IN THE CERRADO OF BRAZIL
Crop weather....................................................... 13
Residual effects of lime rates and depth of incorporation........................ 16
Residual effects of phosphorus applications ................................. 26
Residual effect of lime and phosphorus applications on the loamy
red yellow latosol ................................................ 32
Residual effects of zinc applications...................................... 34
Nitrogen fertilization.................................................'36
Tolerance to aluminum toxicity and low available soil phosphorus................. 40
Management of water stress periods...................................... 65
AMAZON JUNGLE OF PERU
Crop weather ...................................................... 117
Continuous cropping experiment........................................ 117
Multiple cropping experiment .......................................... 137
Liming monoculture and intercropped systems.............................. 152
Mulching and green manuring studies..................................... 166
Phosphorus and sulfur fertilization....................................... 180
Secondary and micronutrient studies..................................... 183
Varieties and plant population studies with corn............................. 192
Adaptation of potatoes to the lowland tropics ............................... 194
CENTRAL AMERICA
Nitrogen response by a corn-cassava intercropped system in the Atlantic
Coast of Costa Rica ............................................... 197
Nitrogen fertilization of beans in relay-intercropped corn and beans in
Alajuela, Costa Rica .............................................. 200
Nitrogen management for upland rice in Costa Rica ........................... 201
Accumulation of dry matter and nutrients by cassava .......................... 209
Phosphorus fertilization in Guatemala .................................... 220
Fertilization of forage sorghum in El Salvador ............................... 222




Page
FERTILITY CAPABILITY SOIL CLASSIFICATION SYSTEM
Evaluation of the "i" modifier with corn experiments from Brazil................. 239
System evaluation in Colombia ......................................... 240
Improving the "i" modifier............................................ 244
SOIL CHARACTERIZATION
Characteristics of a common toposequence in the Llanos Orientales
of Colombia.................................................... 253
Soil-landscape relationship in an area of the Occidental Plateau of
Sao Paulo, Brazil................................................. 270
Characterization and genesis of soils of a climosequence in the Occidental
Coast of Maracaibo Lake, Venezuela................................... 278
Influence of iron oxides on soil color..................................... 280
Ultisols and Oxisols of the savannas and Amazon territory of Venezuela ............ 285
Jenaro Herrera colonization in the Amazon of Peru ........................... 287
Comparison of jungle and savanna soil conditions between South America
and West Africa................................................. 287
Effects of heating on changes in soil properties in relation to an Ethiopian
management practice............................................. 296
ECONOMIC INTERPRETATION WORK PLAN ................................ 305
COMMUNICATION OF RESULTS
Publications ....................................................... 309
Mailing list ........................................................ 310
Conferences and symposia............................................. 310
Utilization at the farmer's level ......................................... 312




INTRODUCTION







3
This is the fifth annual report of the Soil The second activity is the development of Science Department's Tropical Soils Re- the Fertility-Capability Soil Classification
search Program, supported by the U.S. System as a practical tool for grouping soils
Agency for International Development. Con- with similar fertility limitations and thus, tract AID/csd 2806 expired on June 30, to bridge the gap between the subdisciplines
1975 and on that date the program was ex- of soil survey and soil fertility.
tended for an additional three-year period as A third component of the extrapolation Contract AID/ta-C-1236. The overall objec- strategy is an economic interpretation of the tives of the program have been focused more data gathered in a way which evaluates the sharply during the project renewal process profitability of the soil management systems into four major objectives. The first three proposed and at the same time provides phyconsist of developing economical ly-sou nd sical coefficients for economic planning soil management systems for 1) acid tropical tools such as linear programming and sector savannas, 2) tropical rainforests and 3) for analysis. intensive intercropping systems in areas af- The format of this report now identifies fected by volcanic activity. The field re- the staff responsible for each research prosearch activities,to achieve each of these ob- ject in order to give more direct credit to the jectives, continue to be based in Brasilia, people involved both from North Carolina Brazil for the savannas, Yurimaguas, Peru for State University and the cooperating instituthe jungle areas and Turrialba, Costa Rica tions. for the intensive cropping systems. The latter location serves as headquarters for work HIGHLIGHTS OF THE YEAR throughout Central America. Savannas
The fourth objective is to gather addi- The long-term residual effects of liming
tional information needed for establishing a and fertilizer applications on Oxisols of the sound basis for extrapolating the research re- Cerrado of Brazil provided additional inforsults to other tropical areas around the mation as most experiments completed their
world with similar soil management prob- third year after establishment. Original applilems. Three main activities are performed to cations of 2 to 8 tons/ha incorporated deep achieve this objective. Soil characterization (0-30 cm) were able to maintain from 72 to studies, to determine the soil properties of 97% of the maximum corn yields. Shallow little-known tropical areas along with basic (0-15 cm) lime incorporations did not pergreenhouse and laboratory studies, are de- form as well. Chemical analysis suggests a signed to understand certain basic concepts considerable movement of exchangeable calnot presently understood. cium and magnesium below the zone of applications.




4
Phosphorus management continues to be sorghum variety, Taylor Evans Y-101, prothe most crucial fertility parameter for de- duced 6 tons/ha of grain with only 1 ton/ha veloping economically-sound systems. The of lime applied three years before, with a
long-term residual phosphorus experiment, 50% Al saturation in the top 30 cms. The now in its fifth consecutive crop, shows that susceptible variety RS-610 produced the a broadcast initial application of 80 kg same yield with 4 tons/ha of lime and 20%
P205/ha as superphosphate followed by Al saturation in the top 30 cms. Many
band applications at the same rate before varieties developed under acid conditions in each planting produces about 80% of the southern Brazil exhibit joint tolerance to
yields obtained by a massive initial broadcast aluminum toxicity and low available soil application of 1280 kg P205/ha. The resid- phosphorus levels in sharp contrast with ual effect of cheaper sources of phosphorus CIMMYT's Mexican varieties developed uncontinued to show the good performance of der calcareous soil conditions. These results high reactivity rock phosphates. With time have stimulated national breeding programs the low reactivity Araxd rock phosphate in- of corn and sorghum to include joint tolercreased its effectiveness dramatically. Ter- ance as breeding objectives. Coupled with mofosfato, a thermal alteration of Arax6 other management practices identified earfused with magnesium silicate, continued to lier, such as deep liming, combination of perform as well as superphosphate. broadcast + banded phosphorus and cheaper
The residual studies of zinc fertilization sources of phosphorus, the identification show that an initial rate of 9 kg Zn/ha is suf- and use of tolerant varieties will make ecoficient to maintain maximum corn and sor- nomically feasible the opening of new acid ghum yields three years after applications, savanna areas for intensive crop production.
A methodology for screening varieties for Crop physiology during water stress perjoint tolerance to aluminum toxicity and iods was better understood through growth low available soil phosphorus levels was de- analysis monitoring leaf area index, soil temveloped in the greenhouse and tested suc- perature, soil water use, transpiration rates, cessfully in the field. Several varieties of stomatal resistance, leaf water potential, corn, beans, wheat, sorghum and rice were root distribution, yields and nutrient uptake. identified as showing joint tolerance to the These measurements confirm the superiority two most adverse factors of Cerrado soils. of deep liming as a better way to utilize soil When tested in the field, they approached moisture during water stress periods in corn. maximum yields at much lower levels of Upland rice, however, did not benefit from
lime and phosphorus applications than the deep liming probably because of its greater sensitive variety. For example, the tolerant tolerance to aluminum levels.




5
Mulching corn with grass reduced soil ha, 24 kg S/ha, 3 kg Zn/ha, 3 kg Cu/ha,
temperature by 2-3 degrees Centigrade in 1 kg B/ha and 0.1 kg Mo/ha) pests were conboth seasons while a black plastic mulch in- trolled and mulches and herbicides used to creased soil temperatures by that amount, diminish soil compaction, the yields inBoth mulches decreased water stress. creased again. Next year's annual report will Coupled with deep liming, grass mulch dur- show upland rice yields of over 3 tons/ha, ing the hot rainy season and black plastic corn yields of over 4 tons/ha and soybean mulch during the dry season increased yields yields of over 2 tons/ha. Preliminary ecosignificantly. nomic analysis shows that these fertilization
Amazon Jungle rates are profitable.
The continuous cropping experiment suf- Research on multiple cropping combinafered a severe yield decline during 1975 even tions showed that five basic crops (corn, when levels of fertilization and liming con- rice, cassava, peanuts and cowpeas) could be sidered adequate were applied. The causes grown on the same land during one year,
for this decline were not related to age after producing about 30% more food and net inclearing or to climate. They were identified come to the farmers than when the crops as insufficient rates of fertilization and lim- were grown separately. ing, poor germination and initial stands, soil Although the response to lime is great in compaction and increased insect attacks. these acid jungle Ultisols, the residual effect
Soil analysis confirmed that the fertiliza- of lime applications is not as long as that obtion rates applied in 1972 are no longer ade- served in the savanna Oxisols. Continuously quate. Nutrient requirements increased as humid weather, the use of Ca(OH)2 as the
the soil approached a new equilibrium level. lime source and the rapid increases in exMagnesium and potassium deficiencies changeable aluminum a few months after occurred and also an imbalance between Ca, liming are some of the reasons why. IncorMg and K. The residual effect of phosphorus porating lime with a hoe, or simply raking it applications was shorter than expected. Poor on the surface gave very favorable responses germination and initial stands of rice were and opened practical possibilities in small corrected by selecting fungus-free seeds and farming systems where mechanization is difinsect attacks controlled. Soil compaction ficult. problems became evident and were corrected Mulching or incorporating guinea grass or
by mulching and/or herbicide applications to kudzu increased crop yields significantly minimize manual weeding. When fertilizer over four successive crops, and prevented
applications were increased (to 180-160-150 yield declines in unfertilized fields. Mulching kg/ha of N, P205 and K20 plus 50 kg MgO/ decreased soil temperatures by about 5 de-




grees Centigrade, prevented compaction, basic data for the understanding of this basic
conserved soil moisture and decreased weed food crop. Phosphorus fertilization studies growth. Green manure applications did all of in the Altiplano and Pacific coast of Guatethe above except for decreasing soil tempera- mala showed that no massive phosphorus aptures. When crops were intensively fertilized, plications are needed to produce adequate the yield response to these residue applica- corn and wheat yields. Producing intensively tions diminished. fertilized forage sorghum during the rainy
The responses to sulfur, magnesium, po- season in El Salvador to provide silage for
tassium and micronutrients were also identi- dry season feeding of livestock was proved fied and quantified. This led to the formula- to be economically sound. tion of recommended fertilization rates Extrapolation Studies
which increased corn and soybean yields dra- The first formal version of the Fertilitymatically. Capability Soil Classification System was
Field adaptation of Irish potatoes to the published. It is presently being used in lowland tropics was conducted with germ- Colombia, Venezuela, El Salvador and tested
plasm and supervision of the International in other countries, including the United Potato Center. The preliminary results show States. Its applicability to Colombian data considerable promise. was tested. Problems were found in several
Central America regions related to the use of the parameter
Research on multiple cropping systems designed to identify high phosphorus fixashowed that a corn-cassava intercropped sys- tion by iron compounds. It was found that tem in the Atlantic coast of Costa Rica pro- phosphorus fixation could be predicted by duced as much yield of both crops per hec- the clay content of Oxisols and Ultisols or tare as two hectares of monoculture. In the by the product of % clay x % free Fe203. ubiquitous corn-beans relay intercropped Soil characterization studies were consystem practiced throughout the region, re- ducted in areas with very little prior inforsuits showed that nitrogen applications to mation in the interior of South America. A the beans after doubling the corn, increased toposequence study in the Llanos Orientales bean yields significantly and economically. of Colombia indicates that all soils are clasThe efficiency of nitrogen applications to sified as Oxisols and that they differ only upland rice in the Pacific coast of Costa slightly in their chemical and mineralogical
Rica showed an optimum application rate of properties, except for organic carbon which 110 kg N/ha. A thorough study of dry mat- seems to be closely related with soil moister and nutrient accumulation by cassava ture regime. A second study in the Occidenwas completed during the year. It provides tal Plateau of S~o Paulo State, Brazil shows




7
that most soil variation was related to parent The economic interpretation project termaterial and geomorphology. In this minated its initial phase of analyzing already
region Oxisols, Ultisols and Mollisols occur existing data, finding the most appropriate in close proximity. A third savanna region in models for arriving at fertilizer rate recomthe west coast of the Maracaibo Lake in mendations. A new phase was started in late
Venezuela, showed that soils varied from 1975 consisting of interpreting and analyAridisols to Alfisols and Ultisols, depending zing data produced by our program in Yurion soil moisture regime. Basic studies also maguas and Brasilia as a basic tool for linear began on the relevance of yellow and red soil programming and sector analysis studies. colors on iron oxide composition and management implications. Characterization of COLLABORATING INSTITUTIONS AND
Oxisols and Ultisols of the Venezuelan sa- INDIVIDUALS vannas and Amazon Jungle is also in pro- The research reported is conducted in
gress. At the request of the Ministry of cooperation with several national and interFood, soils of the Jenaro Herrera coloniza- national institutions, involving a high degree tion project in the jungle of Peru were col- of collaboration. lected for characterization. In the Cerrado of Brazil, this project is
A study trip through Nigeria, Ghana and conducted jointly with Cornell University
Upper Volta permitted a comparison of jun- and the Empresa Brasileira de Pesquisa Agrogle and savanna soil conditions between pecu~ria (EMBRAPA) at the Centro de Pesthese areas of West Africa and South Amer- quisa Agropecu~ria dos Cerrados, located ica. The similarities in soil management about 40 km north of Brasilia. The USAID
problems are very close in both jungle areas Mission in Brasilia and the Interamerican Inalthough the West African regions visited stitute of Agricultural Sciences provided
have less soil fertility problems and more soil valuable logistical support. EMBRAPA has physical problems than in the Amazon Jun- assigned Mr. Edson Lobato as project leader,
gle. The similarities in vegetation are very representing Brazil. Cornell and N. C. State striking between the Cerrado and the Guinea staff stationed at the Cerrado Center form savannas of Ghana. However, the soils are an integral part of the Center's research
totally different and require completely dif- staff. ferent approaches. A study of the effects of In the Amazon Jungle of Peru, field reburning the soil itself rather than the vegeta- search is conducted at the Yurimaguas Extion was conducted with an Ethiopian soil in periment Station which is part of the Centro order to gather a basic understanding of the Regional de Investigaciones Agropecuarias "guie" system of shifting cultivation prac- del Nor-oriente of the Ministerio de Alimenticed in that country. taci6n. Supporting laboratory work is con-




8
ducted at La Molina. The Direcci6n General The following individuals from the difde Investigaciones of the Ministry has assigned ferent cooperating institutions provided subDr. Carlos Valverde as project leader, repre- stantial administrative support or are cosenting Peru. Dr. Valverde has been very ef- authors of some of the research projects. We fective in expediting administrative matters wish to acknowledge and recognize their assiswith the Peruvian Government. The Interna- tance at this time. tional Potato Center plays a major role in pro- BRAZIL viding administrative and logistical support. In Josd Ireneu Cabral, President of EMBRAPA turn, the program grows its potato trials at Almiro Blumenschein, Director of EMBRAPA Yurimaguas as the lowland tropical station for Wenceslau G. Goedert, Associate Director, adapting potatoes to the region. CPAC, EMBRAPA
In Central America joint projects are con- Edson Lobato, EMBRAPA Project Coordiducted with the Centro Agron6mico Tropical nator
de Investigaci6n y Ensehanza (CATIE) at Gilberto Paez, Head of the Data Processing
Turrialba, Costa Rica; the Ministries of Agri- Department, EMBRAPA culture of Costa Rica and El Salvador and the Wilson V. Soares, former Associate Director, Instituto de Ciencias y Tecnologi'a of Guate- Cerrado Center mala. Activities are also linked with the Inter- Jos4 M. Barcellos, former Head of the Brasilia national Soil Fertility Evaluation and Im- Experiment Station
provement Program (ISFEIP). Logistical sup- William Rodgers, Agriculture and Rural port is provided by CAT I E. Program plans are Development Officer, USAID-Brasilia coordinated with the ROCAP offices of AID William Gelabert, Acting Director, USAID
in the region. Mission to Brazil
Several extrapolation studies are also colla- John Young, USAID-Brasilia
borative in nature. Data for evaluating the Matthew Drosdoff, Professor of Tropical Fertility-Capability Soil Classification System Soils, Cornell University has been provided by EMBRAPA, the Insti- David R. Bouldin, Professor of Soil Science,
tuto Colombiano Agropecuario, Instituto Cornell University
Geogrdfico Agustfn Codazzi in Colombia. Soil Robert B. Musgrave, Professor of Agronomy, characterization studies have been conducted Cornell University with partial financial support in the form of Elicios Martins, Research Technician, scholarships for graduate students from the Cornell-NCSU Project
USAID Mission to Colombia, the Ministerio Clibas Vieira, Professor, Universidade de
de Obras P~blicas of Venezuela, the Fondo de Vigosa Amparo a la Pesquisa do Estado de Sio Paulo, Robert Schaffert, Brasilian National Sorghum Brazil. Program




9
Ady Raul da Silva, Brazilian National Wheat Rollo Ehrich, Deputy Food and Agriculture
Program-CPAC Officer, USAID-Lima
Knut Mikaelson, Centro de Energia Nuclear COSTA RICA
na Agricultura Manuel Elgueta, Director, CATIE, Turrialba
PERU Eladio Carmona, Director de Investigaciones,
Mariano Segura B., Director General de Inves- MAG, San Jos6
tigaciones Agrarias, Lima Alberto Vargas, Subdirector de InvestigaCarlos Valverde S., Project Coordinator for ciones, MAG, San Jos6
the Ministry of Food and Director of the Jorge Soria, Jefe, Departamento de Suelos y
Centro Regional de Investigaciones I-La Cultivos Tropicales, CATIE
Molina Arnoldo Romero, Rice Specialist, MAG,
Manuel Llaveri'a, Director del Centro Regional Palmar Norte
de InvestigacionesAgrarias I II-Tarapoto Carlos Gonzalez, MAG, Los Diamantes Jos6 del Carmen Muro, Director de Investiga- Antonio M. Pinchinat, Plant Breeder, CATIE,
ciones, Ministerio de Agricultura, DGIA, Turrialba
Lima Rufo Bazdn, Soil Scientist, CATIE, Turrialba
Ruben Mesta P., Head, Yurimaguas Experi- Nicolds Mateo, Agronomist, CATIE, Turrialba
ment Station Gerardo Ramfrez, Soils Research, MAG,
Carmen Torres, Soils Department, La Molina San Jos6
Experiment Station Rolando Gonzalez, Rice Program, MAG,
Mario Cano, Soils Department, La Molina Liberia
Experiment Station Roger Menenses, Agronomist, MAG, Los
Humberto Mendoza, Plant Breeder, Inter- Diamantes
national Potato Center Guillermo Iglesias, Soils Section, MAG, San
Richard L. Sawyer, Director General, Interna- Jos6
tional Potato Center Rafael Salazar, Soils Section, MAG, San
Carlos Bohl P., Executive Director, Inter- Jos6
national Potato Center EL SALVADOR
William Hamann, Assistant Executive Armando Alas, Director of Research, CENTA,
Director, International Potato Center Santa Tecla
Oscar Gil, Controller, International Potato Jos6 Perez Guerra, Director of Extension,
Center Centa, Santa Tecla
Veronica de Franciosi, Assistant to Execu- Jorge Alfaro, Head, Soils Research, CENTA,
tive Officer, International Potato Center Santa Tecla
Milton Lau, Food and Agriculture Officer, Francisco Rodriguez, Peace Corps Ag. Coord.,
USAID- Lima San Salvador




10
Jack Morse, Food and Agriculture Officer, Charles A. Francis, Plant Breeder, CIAT,
USAID-San Salvador Palmira
Julio A. Ringuelet, IICA Representative,
San Salvador
Jos6 Antenor Romero, Livestock Extension,
CENTA, Santa Tecla
Edmidlia Guzmdn de Pefia, Soils Investigation, CENTA, Santa Tecla
Julia de Men6ndez, Soils Analysis, CENTA,
Santa Tecla
Harry Brokish, Peace Corps, CENTA, Santa
Tecla
Miguel Fuentes Velarde, Extension, CENTA,
Olomega
Jos6 Elias Ventura, Extension, CENTA, San
Francisco Gotera
Ralph Kramer, Peace Corps, San Francisco
Gotera
Gary Larson, Peace Corps, Villa Dolores GUATEMALA
Anibal Palencia, Head Plant Nutrition, ICTA Luis Estrada, Assistant Soil Scientist, ICTA Julio Brolo, Assistant Soil Scientist, ICTA Ramiro Ortiz, Assistant Soil Scientist, ICTA James L. Walker, Regional Director, ISFEIP Donald R. Feister, Rural Development
Officer, ROCAP-USAID
Morgan Stickney, Assistant Regional Development Officer, ROCAP-USAID COLOMBIA
Servio T. Benavides, Instituto Geogrbfico
Agustrn Codazzi, BogotS
Luis Alfredo Leon, Instituto Colombiano
Agropecuario, Palmira
James M. Spain, Soil Scientist, CIAT, Palmira




JOINT NCSU-CORNELL
RESEARCH AT THE CERRADO CENTER OF BRAZIL
Extrapolation experiment in the loamy, Red Yellow Latosol at the Cerrado Center.







13
This report covers field work conducted we have studied more thoroughly. Table 2.1 from October 1974 to September 1975, en- shows the effect of seasons on tasseling date
compassing a full agricultural year with the and the number of days between 50% tassel1974-1975 rainy season and the 1975 dry ing and black spot formation. Corn grain
season. Research conducted independently yields during the dry season averaged 1.31
of the seasons is also reported. Unless other- tons/ha (about 20%) more than during wise specified all field experiments were con- the rainy season, at near optimum soil fertilducted on a Dark Red Latosol (Typic Haplu- ity levels and water availability. stox, fine, kaolinitic, isohyperthermic) loca- Although the mean daily thermal units ted on a second erosion surface at the Cen- are higher during the rainy season, the total tro de Pesquisa Agropecuaria dos Cerrados thermal units per crop are superior in the
(CPAC) near Brasilia. The properties of this dry season because of the longer growth dusoil were described in the 1973 Annual Re- ration. Table 2.1 also shows that the mean port and are typical of acid Oxisols of tropi- daily solar thermal units are higher during cal savannas. the rainy season but that the total solar
thermal units per crop are higher during the
CROP WEATHER dry season.
D. E. Bandy The differences in solar radiation beThe monthly rainfall and solar radiation tween rainy and dry seasons are not very regime at CPAC is shown in Figure 2.1 in marked as compared with other regions
comparison with the long-term rainfall aver- where solar radiation is substantially higher age. The monthly rainfall distribution during during the dry season. A more accurate the rainy season was unusually uniform but study of these differences can be made by it included two short-term drought periods measuring the photosynthetically active ra(veranicos). The first one lasted for nine diation (PAR). Figure 2.2 shows average days at the end of January 1975 but did not values expressed in quantum units of light. cause serious water stress due to cloudiness The daily average PAR for the rainy season and high humidity. A severe 18-day veranico is approximately 15% more than the dry seadid occur from February 27 through March son, even with the more cloudy weather.
16, 1975 at the grain formation stage of The additional 7.7 days between flowering
many crops. These periods are normal and and black spot formation (the grain filling
play a major role in crop performance. stage) during the dry season can account for
As data from successive years is gathered an additional 1.17 tons/ha of yield assuming the effects of climatic characteristics on crop a 4.9 g/day increase in ear dry weight. The behavior became more apparent. The follow- remainder of the difference in yields being observations are based on corn, the crop tween the seasons is probably related to dis-




14
Table 2.1 Effect of seasons (rainy vs. dry, irrigated) on corn growth stages and yields,
the number of thermal units and the solar thermal units received by corn crop. Average of six rainy season experiments and four dry season experiments conducted at CPAC from 1972 to 1975.
Dry
Rainy Season
Parameter Season (irrigated)
Days to 50% flowering 72.4 99.5
Days from 50% flowering to black spot formation 62.8 70.5
Mean grain yields (tons/ha)!! 6.57 7.88
Total thermal units per crop 5059 6087
Mean daily solar thermal units 18,232 16,337
Total solar thermal units per crop x 106 1.27 1.48
1/At optimum or near optimum soil fertility and water availability
C 600
0
Brasilia (CPAC)
a
o50 -= 500 I-Rainy SeasoV --I
0
E Solar Radiation->
u- 400- 1974-1975
(I) 0 94 17
CL
a> ~300o) Rainfall-.>16- : 200 1974-1975i.
0
00
"00 ~~35 year average
J A S 0 ND J F M AM J
Figure 2.1 Rainfall and solar radiation pattern at the Cerrado
Research Center near Brasilia during the report period.




15
2500
a/ \--Rainy Season
S 2000 / \ (Jan 14-19, 29-30, 1975)
0
(1) 1500
0
4
0600 1200 1400 1600 1800
Time (hrs)
Figure 2.2 comparison of rainy and dry season photosynthetic active Dryradiation m eason corn.
2 500(Aug 30- Sept 10, 1974)
0.0
O060O 0800 1000 1200 1400 1600 1800
Time (hrs)
Figure 2.2 Comparison of rainy and dry season photosynthetic active radiation measurements on corn.




16
ease and insect problems and the irregularity Mg/ha as MgSO4 and a banded application of rainfall. If the assumption that the main of 150 kg P205/ha as triple superphosphate reason for lower yields during the wet sea- and 20 kg N/ha as ammonium sulfate. This son is a shorter grain filling stage is correct, was followed by two sidedressed applicathen the planting date for rainy season corn tions totaling 200 kg N/ha as urea. The racrop should be as near the start of the rainy toon crop was not fertilized. No additional season as possible. lime has been added to this experiment
since the original application of December
RESIDUAL EFFECTS OF LIME RATES 1972.
AND DEPTH OF INCORPORATION Varietal Differences in Sorghum
J. G. Salinas, E. Gonzalez, E. J. Kamprath, The grain yields of the fourth consecP. A. Sanchez, W. V. Soares utive crop are shown in Figure 2.3. Deep
The long term field experiment where lime incorporation was statistically supelime was applied at four different rates and rior to shallow incorporation only at the two depths of incorporation was modified 1 ton/ha rate. There were no differences at
during the 1974-1975 rainy season to ac- the higher rates as it was observed in the
complish an additional objective: test vari- first and second consecutive crops (1973 etal differences with respect to aluminum and 1974 Annual Reports). The large diftolerance. The residual effects of lime appli- ference in this experiment, however, was cations and the related changes in soil pro- the contrasting response between the two perties and root development continued to hybrids. Taylor Evans produced dramatbe measured. ically higher yields than RS-610 at the 0,
Two grain sorghum hybrids, Taylor 1 and 2 tons/ha levels of lime. At higher
Evans Y-101 and RS-610 were supplied by rates, the differences tended to disappear.
plant breeders of the EMBRAPA Corn and In general, Taylor Evans produced the same
Sorghum Research Center in Ste Lagoas be- yield with half the rate of lime as RS-610.
cause differential tolerance to aluminum was Figure 2.4 shows that the differential
suspected. The original plots were split in response of these hybrids is closely related half and sorghum was planted on November to the percent aluminum saturation of the
7, 1974 in 60 cm rows at an approximate top 15 cms. Taylor Evans showed a slower
population of 250,000 plants/ha. The crop rate of yield reduction with increasing aluwas harvested on March 11, 1975, after minum saturation than RS-610. At 40% Al
which a ratoon crop was allowed to grow. saturation, for example, Taylor Evans proThe main crop received broadcast applica- duced only 27% of the maximum yield at
tions of 150 kg K20/ha as KCI and 50 kg the same level of aluminum saturation.




17
.8
Shallow Incorporation (0-15cm) Deep Incorporation (0-30cm)
S
u)6
5
c4
O A Taylor Evans Y-101
0 RS-610
-CP
0
) I I I I
0 1 2 4 8 0 1 2 4 8
Lime Applied in 1972 (tons/ha)
Figure 2.3 Differential response of two grain sorghum varieties to rates and
depth of lime incorporation. Brasilia, 1974-1975 rainy season.
Below: Mr. Jos6 Salinas compares the two sorghum varieties in unlimed plots. Left: RS-610. Right: Taylor Evans-lOl.




18
The ability of the sorghum plants to shown in Figure 2.6. Although there was no
proliferate under high levels of aluminum response to depth of liming in the second an
saturation was related to the yield differ- and fourth crop, the overall trend shows a ences. Figure 2.5 shows the relationship be- positive advantage of this practice. Incorportween root lengths and aluminum saturation ating lime to 30 cms in effect decreased the in the top 15 cms. Deep liming applications lime rate needed to attain specific yield by increased root lengths in both varieties. A half. As discussed in the previous annual recomparison of root lengths in the 15-30 cm ports, the advantages of deep lime applicasoil depth increment for the two shallow and tions are related to increasing root proliferadeep lime incorporations is shown in Table tion which, in turn, allows for better soil 2.2 at the rates of 1 and 4 tons/ha. Root moisture and nutrient utilization. This favorlengths increased in both hybrids with deep able effect can be expected in other soils lime incorporation but the effect was most with high aluminum saturation in the subpronounced in RS-610, the susceptible hy- soil. As mentioned in the 1974 Annual Rebrid. port, no beneficial effects of deep liming can
These results show the potential for be expected in soils where the subsoil is not
utilizing aluminum-tolerant cultivars as one aluminum-toxic like the Red Yellow Latosol of the management components for acid on the first erosion surface at CPAC. RouOxisols. A combination of 1 ton/ha of lime tine soil testing for exchangeable aluminum, incorporated deeply three years ago and an calcium and magnesium with depth is recomaluminum-tolerant hybrid produced a high mended as a means for deciding when to ingrain yield of 6 tons/ha. In contrast, the con- corporate lime deeply. ventional practice of shallow liming and an Residual Effects of Liming. aluminum-sensitive sorghum hybrid required An estimation of the residual effects of
4 tons/ha to arrive at the same yield of 6 lime applied in 1972 to the first four grain tons/ha. crops is shown in Figure 2.7, expressed as
The subsequent ratoon crop performed percent maximum yield relative to treatvery poorly due to considerable bird damage ment which always gave the highest absoand poor stand caused by involuntary re- lute yield, 8 tons/ha of lime incorporated
moval of many plants during the first harvest to 30 cms. Among the shallow depths of as a result of the shallow root system in the incorporation, the 1 ton/ha rate has lost unlimed plots. The results are discarded. most of its residual effect, producing only
Cumulative Effects of Liming about 26% of the maximum yield during
The cumulative effect of four consecu- the fourth crop. In comparison, the 2 tive crops (3 of corn and 1 of sorghum) is tons/ha rate produced 72% of the maximum




Percent Aluminum Sat. (0-15cm) 100 10 12 33 42 78
00.- I
E "0 40
E E
%R 8800
10 E
040
Z) 0
7 0- & Taylor Evans YIO101
~I0
0 Ur TE YIOI
____ ____ ____ ____ 0 RS 610
0 20 40 60 80
Percent Aluminum Saturation
Figure 2.4 Effect of aluminum saturation in the top Figure 2.5 Varietal differences of sorghum in rela15 cm on the grain yield of two sorghum tion to root length and percent aluminum
varieties. Brasilia 1974-1975 rainy sea- saturation. Brasilia 1974-1975 rainy
son. season.
CD




20
yield, the 4 ton/ha rate 83%, and the 8 tons! Table 2.3. No major changes in soil pH are ha rates 97%. Consequently, the residual noted. Exchangeable aluminum and percent
effect of these rates is still considerable. aluminum saturation values in the 0-15 cm
The deeply placed treatments, how- layer are increasing with time in all treatever, showed a slower rate of decline in their ments except in 8 tons/ha shallow and deep residual effects. The 1 ton/ha produced treatments. The shallow lime treatments in
about 47% of the maximum yield, while the the 15-30 layer show a decrease in aluminum 2 and 4 tons/ha rates produced 79 and 86% saturation which implies a possible downrespectively. In spite of the lower lime rate wards movement of calcium and magnesium. per unit of soil volume, the residual effect of The overall trend in aluminum saturadeeply incorporated lime is superior to that tion is shown in Figure 2.8. The decrease in of the shallow incorporations. the residual neutralizing effect of the lime
The zig-zag pattern observed in some with time started to be evident after the
treatments with time is typical of data where third crop was harvested, at about 18 relative yields are plotted as a function of months after application, except for the 8 time. The low points are normally associated tons/ha rate in the shallow treatments and with low maximum absolute yields because both 4 and 8 tons/ha rate in the deep treatother limiting factors prevented a full re- ment. The progressive decrease in aluminum sponse to the materials added. This was the saturation with time in the 15-30 cm layer case in the third crop which was adversely of the shallow treatments is also evident in affected by extremely wet weather and sub- this figure. Again, a downwards movement sequent pest and disease attacks (1974 An- of basic cations is suspected. This important nual Report). The overall trend of the experi- phenomenon is being studied in greater dement suggests that a lime rate of 4 tons/ha tail in 1976. deeply incorporated can provide a good re- Soil Solution Studies sidual effect with over 80% of the maximum The soil solution constitutes the most
yield. Deep incorporation of 8 tons/ha re- immediate chemical environment surroundmains the best treatment. ing roots. It is in direct physical contact and
Effects on Soil Properties hence of utmost importance for nutrient
The changes in soil pH, exchangeable availability and for toxicity of certain eleAl and percent aluminum saturation after ments as well. Soil solution studies were
the harvest of the third corn crop (May, made with soil samples taken from field
1974), the harvest of the main sorghum crop plots of each lime treatment during the first (March 1975) and after the harvest of the three crops. A displacement procedure was sorghum regrowth (July 1975) are shown in used to obtain soil solutions. The results




21
Table 2.2 Varietal differences in sorghum root length as related to rate and depth of
lime incorporation.
Lime
applied Depth of Taylor Evans Y-101 RS-610
in 1972 incorporation 0-15cm 15-30cm 0-15cm 15-30cm
tons/ha ---cm- - - - Root length (cm/100 cm soil) -
0 ------ 31 12 17 9
1 0-15 64 20 39 10
4 0-15 169 25 87 19
1 0-30 72 22 45 17
4 0-30 207 37 106 40
25
4 Crops 0-30 cm
S 20
S0- 15 cm

.2 5
E
I I I I
0 I 2 4 8
Lime Applied in 1972
Figure 2.6 Cumulative grain yields of four consecutive crops harvested since
the original lime applications. The fourth crop is the average of
the two sorghum varieties. Brasilia, 1972-1975.




Table 2.3 Soil pH, exchangeable aluminum and percent aluminum saturation after the harvest of the third corn crop and P
the two sorghum harvests as affected by depth and rate of lime applications in 1972.
Soil pH Exchangeable Al Al Saturation
Depth of Lime Soil May March July May March July May March July
lime incorp. rate Depth 1974 1975 1975 1974 1975 1975 1974 1975 1975
- --cm- -- ton/ha -cm- - 1:1 H20- -- -- meq/100g -----%- --
No lime 0 0-15 4.5 4.4 4.5 1.14 1.41 1.36 68 78 69
15-30 4.4 4.3 4.6 1.18 1.25 1.17 73 81 68
Shallow 1 0-15 4.9 4.9 4.9 0.62 0.66 0.91 30 41 48
(0-15) 15-30 4.6 4.6 4.9 0.99 0.97 0.89 60 62 58
2 0-15 5.2 5.0 4.9 0.35 0.56 0.81 15 24 38
15-30 4.6 4.7 4.8 1.08 0.99 0.68 63 57 52
4 0-15 5.6 5.2 5.3 0.09 0.33 0.43 3 12 19
15-30 4.8 4.8 5.0 0.92 0.93 0.57 50 50 32
8 0-15 6.4 6.1 5.6 0.06 0.08 0.08 1 1 2
15-30 4.9 5.3 5.1 0.68 0.55 0.33 20 27 14
Deep 1 0-15 4.9 4.7 4.7 0.89 0.99 0.88 48 32 39
(0-30) 15-30 4.7 4.6 4.8 1.03 1.04 0.96 58 66 60
2 0-15 5.3 5.1 5.0 0.37 0.50 0.64 12 23 34
15-30 4.9 4.8 4.8 0.73 0.78 0.70 40 51 44
4 0-15 5.5 5.4 5.4 0.21 0.26 0.31 9 10 13
15-30 5.1 5.0 5.1 0.51 0.66 0.51 25 35 27
8 0-15 5.9 5.9 5.9 0.07 0.12 0.03 1 1 1
15-30 5.3 5.3 5.4 0.14 0.36 0.13 5 16 5




23
Shallow Placement (0-15cm) Deep Placement (0-30 cm)
Lime rate (4.8) (7.3) (3.6) (7.1)
100 8 --08
4 A, 4
" 60-\
E\
E. 40
0
0 I
1 2 3 4 1 2 3 4
Crop Sequence
Figure 2.7 Residual effect of lime applications expressed as percent
maximum grain yield relative to the yield of the 8 ton/ha deep treatment. Numbers in parentheses show the maximum yields in tons/ha. First three crops corn, fourth sorghum (RS-610 variety). Brasilia, 1974-1975.




24
Table 2.4 Cation concentration and pH of the displaced soil solutions of each lime treatment of lime incorporations. Soil sampled after first crop (May 1973).
Depth of Lime Soil Soil Solution
lime incorp. rate depth pH Al Ca Mg K
cm ton/ha cm ppm
No lime 0 0-15 4.3 1.40 22.8 3.3 25.2
15-30 4.2 1.95 13.4 3.6 27.6
Shallow 1 0-15 4.7 0.49 50.8 4.2 20.8
(0-15) 15-30 4.3 1.82 20.0 3.6 22.8
2 0-15 5.7 0.21 112.4 5.0 26.4
15-30 4.5 1.41 30.4 3.6 22.8
4 0-15 6.4 0.06 109.6 5.5 14.0
15-30 4.3 1.29 37.7 4.8 23.6
8 0-15 7.1 0.05 197.6 5.4 12.6
15-30 4.6 1.02 43.8 4.4 22.6
Deep 1 0-15 4.8 0.64 65.8 6.3 26.8
(0-30) 15-30 4.6 0.81 54.0 5.8 22.8
2 0-15 6.3 0.13 114.0 6.2 12.4
15-30 4.7 0.87 61.4 4.7 20.0
4 0-15 6.8 0.03 137.6 6.5 12.4
15-30 5.9 0.20 76.8 4.5 11.0
8 0-15 6.7 0.00 149.0 6.9 12.2
15-30 6.5 0.21 96.0 4.5 15.0
Table 2.5 Effect of levels of aluminum on root length in the 15-30 cms layer of soil.
Soil sampled after first crop (May 1973).
Lime Al Solution Root
rate satn. AI length
ton/ha % ppm cm/100cm soil
0 79 1.95 147
2 shallow 63 1.41 118
4 shallow 52 1.29 171
4 deep 5 0.20 325
8 deep 5 0.20 346




SHALLOW INCORPORATION (0-15 cm)
0-15 cm Soil Depth Lime 15-30cm Soil Depth
(t/ha) 25
80- 80CO
00
.oO
a 60 60
on 2
4,,
.0
E
40 2 40
E
3 4
4
- 20 208
o8
.
a
I Ill .I
0 I 2 3 4 5 0 I 2 3 4 5
DEEP INCORPORATION (0-30 cm)
0-15cm Soil Depth 15-30cm Soil Depth
80 80
0
4
S60 60
C0
2
(U)
E2
40 40
4
,20- 20",
o4
. 8 8
I I I I I
0 I 2 3 4 5 0 I 2 3 4 5
Crop Sequence
Figure 2.8 Residual effects of lime rates and depth of incorporation
on the aluminum saturation after three corn crops and two
sorghum crops. Brasilia, 1972-1975.




26
for the samples taken after the first corn har- effects of lime will last. vest are presented in Table 2.4.
Aluminum on the exchange site is in RESIDUAL EFFECTS OF PHOSPHORUS
equilibrium with soil solution aluminum. Re- APPLICATIONS moval of exchangeable aluminum by neutral- R. S. Yost, E. J. Kamprath, E. Lobato, ization with the various levels of lime de- G. C. Naderman, W. V. Shares creases the level of aluminum in soil solution Rates, Placement and Timing of Superphosand increases the calcium content. Since cal- phate Applications. citic lime was applied, no increase in magne- A fifth consecutive crop of corn was sium was detected. Lime also seems to de- grown during the 1974-1975 rainy season in crease the potassium content to the depth of order to continue evaluating the cumulative lime application, or residual effects of ordinary superphosA consistent relationship was found phate applications. The experimental design
between the soluble forms of aluminum,soil and methodology has been reported in the solution and reduction in root growth (Table previous annual reports. A decision was 2.5). This relationship emphasizes the effect made to stop further banded phosphorus apthat high concentrations of aluminum in so- plications after the fourth crop except for lution have on the root system of corn. Treatment number 10 (80 broadcast + 80
The shallow application of lime (0-15 banded), the one that had received the least cms) did not have an effect on the 15-30 amount of phosphorus. This permits to comcms soil zone in neutralizing aluminum and pare different treatments at the same levels did not increase root growth in the 15-30 of total phosphorus applied. The nitrogen cm depth. The deep lime application was ef- and potassium applications continued; the fective in decreasing aluminum in the 15-30 residual effects of the 4 tons/ha of lime and cm depth and in increasing the root length. 11 kg Zn/ha were sufficient to produce excelThere was a concomitant increase in the lent corn growth.
level of calcium as lime rates were increased. The yields of the five crops are preFrom this experiment it is not possible to sented in Table 2.6. A strong residual effect separate out the specific effects of aluminum is evident in all treatments. The banded and calcium root growth. However, it is evi- treatments outyielded the broadcast dent that aluminum concentrations must be treatments by about 1 ton/ha at equal rates decreased in order for calcium to have a of phosphorus applied since 1972. Figure
beneficial effect on root growth. The field 2.9 shows the trends expressed in relative experiment is being continued by CPAC yields. The residual effects of the original
scientists to determine how long the residual broadcast treatments continue to depend on




27
.Broadcast in 1972 Banded before Crops 1-4
1280 320
" 100 10--0---------o (33)
o. 35) 160
80 640 80
L2 0~(28) (21
0% 320 6
04 i40 40-((20)
0 !.. e20
0 20
0 2 *I-. 3) 20/ I I I I I 0 I
I 2 3 4 5 I 2 3 4 5
Broadcast + Banded
~I00 before each crop 100 80 Bcst + 80 Band. (25)
> 80 '320 Bcst. + 320 Band.(30)
E Successive applications
E No additional P
40 applications
O 20
I n I I
0 1 2 3 4 5
Consecutive Corn Crops (1972 -1975)
Figure 2.9 Effects of rate, placement and residual or ordinary superphosphate applications to five continuous corn crops. Grain yields expressed as percent of the 1280 broadcast treatments. Numbers in parentheses are the cumulative grain yields in tons/ha. Brasilia, 1972-1975.




28
the initial phosphorus rate. The 160 kg traction which serves as the basis for fertilP205/ha treatment is only producing about izer recommendations in the Cerrado. Table 20% of the maximum yield, the 320 kg 2.7 shows the generally decreasing trend
P205/ha about 50% and the 540 kg with time. Comparing this table with the
P205/ha treatment about 80% of the yield preceeding figure, it shows that a level of 9
obtained by the 1280 kg P205/ha broad- ppm P was needed to produce more than
cast rate. The residual effect of four ban- 80% of the maximum yields. If this trend ded applications was strong during the fifth continues, the residual effect of the 1280 crop. Because of the low initial yields dur- kg P205/ha rates should be expected to ing the first and second crops, the cumula- last several more years. This experiment tive yields are similar between the banded will be continued by CPAC staff members and broadcast treatments at the same levels in order to fully evaluate the residual efof total phosphorus applied (Table 2.6). fects.
The most practical approach appears Phosphorus Sources on Pastures
to be the combination of an initial broad- In February 1974 two parallel expericast application followed by a banded ap- ments were planted to evaluate the effects plication of 80 kg P205/ha before each of cheaper sources of phosphorus in order
crop. When 320 kg P205/ha was broad- to decrease the costs of applications. The
cast initially and was followed by four ban- two high solubility rock phosphates, Hiperded 80 kg P205/ha applications (Treat- fosfato (North African) and North Carolina
ment 9) the yields were maintained at provided similar early growth as ordinary
about 80% of the maximum with a total superphosphate. The low solubility Arax6
phosphorus application of 640 kg P205/ha rock phosphate produced very little When the initial broadcast application was growth, but when it was thermally altered only 80 kg P205/ha and was followed by as Termofosfato the performance was simfive banded applications at the same rate ilar to superphosphate. In addition, Termo(Treatment 10) the cumulative yield was fosfato produced a significant liming effect.
71% of the maximum. These latter two The design and the properties of these mastrategies appear to be most promising terials were described in the 1974 Annual
ways of managing superphosphate applica- Report. The growth of Stylosanthes hutions in this Oxisol with an extremely high milis was very poor and thus, the results are phosphorus fixation capacity. not presented.
The changes in available phosphorus Figure 2.10 shows the results during
have been monitored after each harvest the 1974-1975 rainy season for Brachiaria
using the North Carolina double acid ex- decumbens. Results of these harvests indi-




Table 2.6 Grain yields of five successive corn crops (Cargill-lll hybrid) as affected by rate, placement,
timing, and residual effects of ordinary superphosphate applications.
Consecutive Corn Yields
Initial Banded Total 1 2 3 4 5 Total
Treatment broadcast application2 applied Rainy Dry Rainy Dry Rainy five Maximum
Number application!I/ per crop- in 5 crops 72-73 73 73-74 74 74-75 crops yields
---------------kg P205/ha -----------------------------tons/ha ----------------
1 160 0 160 5.23 3.27 0.87 1.78 1.65 12.80 36
2 320 0 320 6.27 5.68 2.20 3.42 3.00 20.57 58
3 640 0 640 6.79 7.48 2.97 6.43 4.82 28.49 80
4 1280 0 1280 7.96 8.53 3.86 9.09 6.25 35.69 100
5 2000 0 2000 2.26 9.54 4.56 9.02 6.60 31.98 90
6 0 80 320 2.42 5.08 3.08 6.03 4.49 21.10 59
7 0 160 640 3.85 6.57 3.41 8.07 5.86 27.76 78
8 0 320 1280 4.79 8.42 4.19 9.03 6.89 33.32 93
9 320 80 640 6.65 7.32 3.33 7.22 5.40 29.92 84
10 80 80 480 4.56 6.00 2.56 6.48 5.79 25.39 71
LSD.05 0.67 0.65 0.88 0.79 0.67
I/All applied on November 1972 except for Treatment 5 which received 80 kg P205/ha on November 1972 and 1920
kg P205/ha after the first crop on June 1973.
2/All banded applications stopped after the fourth crop, except for Treatment 10 which continued on the fifth crop.




30
Table 2.7 Soil test values for phosphorus (North Carolina dilute double acid method) after
each corn harvest in the broadcast treatments.
Broadcast 1 2 3 4 5
P applied Rainy Dry Rainy Dry Rainy
in 1972 72-73 73 73-74 74 74-75
kg P205/ha- - -Available P(ppm)- - -
160 4.6 3.9 3.6 2.9 3.1
320 8.8 7.4 5.0 4.4 5.1
640 17.7 19.5 10.0 8.0 9.0
1280 68.8 55.8 30.6 25.3 21.9
2000 ---- 103.5 65.6 50.2 42.9
Russell Yost sampling soils in the
residual phosphorus experiment.




31
20 ORDINARY SUPERPHOSPHATE 20 TERMOFOSFATO
SI16- 16
I2 Lime rates 12
8 o 0 8
9 *3
0 I LSD05 a 4.5 4 ILSD05
04
0 0
o 86 345 1380 86 345 1380
I
L.
42 20- 20ARAXA ROCK PHOSPHATE HIPERFOSFATO
16- 16S12 I LSDo5 12
8- 8. N.C. Rock
0 0
86 345 1380 86 345 1380
P Applied in February, 1974 (kg P205/ha)
Figure 2.10 Effects of sources and rates of phosphorus and liming on
annual dry matter production of Brachiaria decumbens. Sum of second and third cuts on December 1974 and March 1975.




32
cate that the high reactivity rock phosphate of equilibration, was 4.4, 5.2, and 5.4 with sources (Hiperfosfato and North Carolina) the respective lime treatments. Lime appliare continuing to supply phorphorus nearly cations tended to increase yields when apas well as the highly soluble ordinary super- plied with soluble phosphate but tended phosphate. The Termofosfato continued to to reduce yields when applied together with
perform as well as superphosphate. slowly soluble rock phosphate sources. ReA comparison of May 1974 yields with suits to date suggest citrate solubility of
March 1975 yields suggests that the availa- these sources was more influential on availbility of Araxg rock phosphate increases ability to this grass than pH variations from
with time (Figure 2.11). This effect appears 4.4 to 5.4. to be somewhat reduced at the higher level As measured by grass yields, the Hiperof lime. Yields of the May 1975 harvest fosfato, North Carolina rock phosphates and
show less response occurred to soluble phos- the Termofosfato, provided nearly as much phorus source levels above 345 kg P205/ha available phosphorus as ordinary superphosthan on earlier harvests. This trend may be phate. The low solubility Arax6 rock phosin part due to a more fully developed root phate appears to be increasing in availability system. with time and may be economically competA treatment of 86 kg P205/ha as ordi- itive in the long run.
nary superphosphate was surface applied
with no incorporation in November 1974. RESIDUAL EFFECT OF LIME AND
The May 1975 yields with this treatment are PHOSPHORUS APPLICATIONS ON THE very high relative to a similar thoroughly in- LOAMY RED YELLOW LATOSOL corporated before grass establishment (Fig- R. S. Yost, K. D. Ritchey, E. Lobato, G. C. ure 2.11). This suggests surface applications Naderman of phosphate on this grass species can be The first extrapolation experiment was
quite effective and that some important initiated last year on the loamy Red Yellow
feeder roots are near the surface. Future har- Latosol located on the first erosion surface vests will assist in determining how effective at CPAC. This type of Oxisol is very extensurface applications are relative to incorpo- sive in the Cerrado and at the location where rated ones. the experiment was installed it differed signiSoil pH determined two months after ficantly from the Dark Red Latosol where
lime application but before phosphate treat- all other experiments have been performed ments were added was 4.4, 4.8, and 5.1 with in a higher available water range and in a lime applications of 0, 3, 4.5 tons/ha, respec- lower aluminum saturation in the subsoil. tively. Soil pH, after three additional months Soil properties and the first year results ap-




33
ORDINARY SUPERPHOSPHATE ARAXA ROCK PHOSPHATE
1.0 May, 1974 1.0 May, 1974
0.8- 0.8 Lime rates:
S0o
0.6- 0.6 3
0.4- 0.4- LSD.05 4.5
00.02LSDO5
0.2- 0.0
0.0 0.0
86 345 1380 86 345 1380
c 10 10
o December, 1974 December, 1974
8 8
6- 6
4- LSD.05 I LSDQ5
12 2 ____0.
o 86 345 1380 86 345 1380
12 March, 1975 12March, 1975
10 surface applied Nov.,1974 10
8- 8
6 6
4 4
LSD.o5
2 2 fLSD.05
0' 0
86 345 1380 86 345 1380
P Applied in February, 1974 (kg P205/ha)
Figure 2.11 Increased availability of AraxS rock phosphate sources with time to Brachiaria decumbens.




34
peared in the 1974 Annual Report. higher than the 400 kg P205/ha broadcast
The second consecutive rainy season the previous year. Sorghum was more recrop was planted on November 1974. Corn sponsive to lime applications than was corn
(Cargill-1 11) was planted on one half of the probably because of lower tolerance to exdouble size plots and grain sorghum (Agro- changeable aluminum. ceres-1001) was planted on the other half. Yields of both crops were high considerThe double sized plots allowed pursuit of ing the occurrence of the two drought pertwo objectives: 1) The study of residual ef- iods during the cropping season. These fects of the original lime and phosphate ap- drought periods required supplemental irriplications with a standard crop and variety gation in the experiments later planted on on a second variant of soils of the Cerrado, the Dark Red Latosol. Even though the exand 2) expand the information to include periment on the loamy Red Yellow Latosol
effects of the fertility treatments to differ- was not irrigated, the yield of corn on this ent crops such as grain sorghum, soybeans, soil was higher than that of the irrigated etc. Fertilizer treatments and yields of corn Dark Red Latosol, 8.9 tons/ha versus 6.6 and grain sorghum are shown in Table 2.8. tons/ha. This yield difference is probably
For comparable phosphorus treatments due to the fact that the Red Yellow Latosol
there was no significant difference between contains 30% more available water at field deep and shallow lime incorporations for capacity in the surface 30 cms, and that the
either crop even though two drought periods lower percent of exchangeable aluminum in occurred during the growing season. Last the Red Yellow Latosol subsoil allows
year the deep lime treatments on this soil greater root penetration of aluminum sensigave higher yields of corn though the differ- tive crops. This experiment points out imences were not significant. These results dif- portant management differences related to fer from those of the experiments on the available water capacity and subsoil acidity Dark Red Latosol where the deep lime incor- among Oxisols with otherwise very similar poration (0-30 cm) has given consistently properties. The experiment will be planted higher yields of maize than the shallow lime again to corn and sorghum for the third conincorporation (0-15 cm). One probable ex- secutive rainy season crops in 1976 by CPAC planation is that the percent aluminum satu- scientists. ration in the 15-30 cm layer of the Red Yellow Latosol is substantially less than that of RESIDUAL EFFECTS OF ZINC APPLIthe Dark Red Latosol, 25 versus 53%. CATIONS
Grain sorghum yields did not respond K. D. Ritchey, F. R. Cox and R. S. Yost
significantly to applications of phosphorus In an effort to evaluate the behavior of




Table 2.8 Residual effects of phosphorus and lime applications on the loamy Red Yellow Latosol on corn
(Cargill-lll) and grain sorghum (Agroceres-lO01) yields.
Treatment P applied in 1973 P applied in 1974 Lime applied
Number Band. Bdc. Band. Bdc. in 1973 Corn Yields Sorghum Yields
--------------kg P205/ha ---------------- tons/ha -- tons/ha* % max. tons/ha* % max.
6 0 2000 0 0 4 deep 8.90 a 100 8.08 a 100
3 100 400 50 0 4 shallow 7.99 b 90 7.82 a 96
7 100 400 100 0 4 shallow 7.69 b 86 8.16 a 100
8 100 400 100 0 4 deep 7.63 b 86 7.36 a 91
2 100 400 50 0 4 deep 7.20 bc 81 7.35 a 91
4 100 400 150 0 4 deep 7.14 bc 80 8.08 a 100
5 0 400 0 0 4 deep 6.67 c 75 7.33 a 91
1 100 400 50 0 no lime 5.85 d 66 3.56 b 44
*Means followed by the same letter are not significantly different at the 5 percent level by Duncan's
Multiple Range Test.
cAn0




36
other crops, the large plots of the residual Zn/ha in all consecutive crops. The 3 kg zinc experiment were also split in two and Zn/ha rate maintained approximately 89% planted to corn and sorghum during the of the maximum yield in all three crops. The
rainy season of 1974-1975. The corn crop yields with no zinc applied have been inwould permit the evaluation of the residual creasing with time. The reasons for this are effects of zinc sulfate applications of Decem- not fully understood. Contamination of Zn ber 1972 with the same hybrid. At the same from adjacent plots with successive tillage is time new data was obtained with grain sor- also a possibility which is being investigated ghum. The subplots received a broadcast ap- during 1976. plication of 150 kg K20/ha as KCI and 160 An additional treatment without boron
kg P205/ha as simple superphosphate at has been included at the 9 kg Zn/ha rate.
planting. The corn was topdressed with 150 This treatment has produced over 90% of kg N/ha as urea and the sorghum with 271 the maximum yield in all crops, which is kg N/ha as urea. Soil samples were taken be- probably within the realm of the experifore planting and analyzed for zinc using mental error. Consequently, no boron defithree different soil test extractants. No addi- ciencies are suspected in this soil. tional zinc, lime, boron or molybdenum has Cate-Nelson diagrams shown in Figure
been applied since 1972. The high lime rate 2.14 for all three years indicate that extractused raised the soil pH level to 6.6 in 1972. able soil zinc levels of 1.4 ppm for 0.1 N
Figure 2.12 shows the results of the HCl, 1.0 ppm for 0.05 N HCI + 0.025 N third consecutive planting. A strong residual H2SO4, and 0.7 ppm for DTPA-TEA appear effect of zinc applications was evident. The to be the critical levels above which there is optimum level for corn appears to be about enough available soil zinc to eliminate zinc 9 kg Zn/ha, which is higher than the level of deficiency on corn on this Dark Red Latosol
3 kg Zn/ha obtained in the previous two limed to pH 6.6.
crops (1974 Annual Report). Sorghum produced a much higher yield than corn with- NITROGEN FERTILIZATION out added zinc and approached maximum K. D. Ritchey and G. C. Naderman
yield at the 1 kg Zn/ha rate. Apparently, For the third continuous corn crop in
sorghum has a lower zinc requirement than the nitrogen experiment grown in the 1974corn, or it is more efficient in extracting 1975 rainy season, last year's experimental zinc. design was modified slightly. The sulfurThe residual effect on corn is shown in coated urea (SCU) treatment was continued Figure 2.13 expressed as a percentage of the but the material was different from that maximum yield which was attained by 9 kg used in either the first or second crop. This




8 3
-; 7
6
(0)
0
- 5"0 4e Corn (Cargill 111)
0 Sorghum (RS-610)
3
1 3 9 26
Zn Applied in 1972 (kg/ha)
Figure 2.12 Yield responses to residual zinc applications by corn
and sorghum (third consecutive crops). Brasilia 1974-75
rainy season.
100- Aq.~-~27
3
- 80E 60 -40 0
40
: 20 Zn/ha
0
0 I 2 3
Consecutive Corn Crops
Figure 2.13 Residual effects of zinc applications in 1972 to three
consecutive corn crops (Cargill-Ill hybrid) growth during
the 1972-1973, 1973-1974 and 1974-1975 rainy seasons in
Brasilia.




0.1N HCI 0.05N HCI + 0.025N H2SO4 DTPA-TEA
100 a a
0 rl 0
00
80
go
60 1972-73 -0
e 1973-74
De o 1974-75 0* Do
40
0
20
S I i I I. I I I I I I I I I I
0 11-4 2 3 4 6 0 I 2 3 4 5 O 0.7 I 1.5 2 2.5 3
Soil Test Zn (ppm)
Figure 2.14 Relationship between percent yield of Cargill-Ill corn (relative to 9 kg/ha Zn)
and soil zinc removed by three extractants for three years.




Table 2.9 Grain yields (15.5 percent moisture) of the third maize crop of the nitrogen experiment at
Brasilia 1974-1975 rainy season.
Treatment 20 days 30 days 61 days/
Number At planting after planting after planting after planting Yield--------------------------------- kg N/ha -------------------------------- kg/ha
9 20 100 0 100 7700 a
8 20. 0 1202/ 0 7438 ab
7 20 60 0 60 7324 ab
5 20 0 120 0 7256 ab
4 20 0 80 0 7015 abc
6 20 40 0 40 6953 abc
1 0 0 80 0 6804 bc
3 20 0 40 0 6336 c
10 1403 / 0 0 0 6254 c
2 0 0 0 0 4201 d
1/Duncan's Multiple Range Test at the 5% level.
2/Lime-coated NH4NO3
3/Sulfur-coated urea 10.1% soluble in 7 days.




40
material had a slower rate of nitrogen release Aluminum toxicity and phosphorus than last year's material (10.1% in 7 days) deficiency frequently occur together in most according to TVA. Maintenance fertilization of the Cerrado Oxisols. Previous work conconsisted of 150 kg K20/ha as KCl broad- ducted in Brasilia has identified both high cast and 100 kg P205/ha applied as a band levels of exchangeable aluminum and low at seeding. The treatment descriptions and available phosphorus as serious limiting facyields for the third maize crop are given in tors of crop production. Up to last year, Table 2.9. phosphorus fertilization and liming to optiGrain yields increased from 4.2 tons! mum levels along with their residual effects, ha with no nitrogen applied to 7.7 tons/ha have been considered the main strategies to with 220 kg N/ha (Figure 2.15). Yields from solving these problems. Tolerance studies on the application of 240 kg N/ha approached aluminum toxicity and low available phosthe maximum. Increasing the number of phorus provide an additional dimension.
sidedressings from one to two did not in- This new strategy does not mean the elimicrease yields. The application of nitrogen as nation of phosphorus fertilization and limammonium nitrate gave about the same yield ing. However, it can decrease phosphorus as that applied as urea. The use of 240 kg fertilizer and lime requirements needed to N/ha as sulfur-coated urea in a band below obtain adequate yields. the seed at planting resulted in reduced Work during the year included both
stands and lower yields. greenhouse and field research with the folDuring the three years of growing lowing objectives: 1) To study the varietal
corn in the nitrogen experiment the coeffi- and species differences in tolerating high cient of variability has gradually decreased levels of aluminum and low levels of availand the yields of the no nitrogen added plots able phosphorus, 2) to identify certain phyhave increased (Table 2.10). This phenom- siological mechanisms responsible for aluenon has been observed in the Cerrado minum-phosphorus interactions in this dual
farms. Calculations on the soil nitrogen re- tolerance, 3) to determine whether green,lease after liming and fertilization with other house tests can be used in lieu of field tests nutrients appear to account for these differ- for certain phases of this dual tolerance. ences. Corn, wheat, beans, sorghum and rice
varieties were tested under greenhouse soluTOLERANCE TO ALUMINUM TOXICITY tion culture and field conditions. Most of
AND LOW AVAILABLE SOIL PHOS- the varieties were provided by Brazilian inPHORUS stitutions on the basis of possible differences
J. G. Salinas and P. A. Sanchez related to aluminum toxicity and phos-




41
8
F NH4NO3
U Sulfur-coated urea
-o
C
0
4
" Applied in furrow at planting
0 One sidedressing A Two sidedressings
SI I I I I
0 60 80 100 140 220
Nitrogen Applied (kg/ha) Figure 2.15 Corn response to nitrogen applications. Third consecutive
crop. Brasilia 1974-1975 (supplied as urea except where
indicated).
Table 2.10 Effect of successive cropping on corn grain yields (Cargill-Ill
hybrid) grown without added N and the coefficients of variability of the experiment.
Grain yields of plots Coefficient of
Crop without added nitrogen variability
Skg/ha -------%
1972-1973 3246 16.9
1973-1974 3757 11.2
1974-1975 4201 8.3




42
phorus deficiency. Varieties were provided twelve samples. by Dr. Robert Shaffert of the National Corn Corn and wheat seeds were germinated
and Sorghum Center at Site Lagoas, Dr. Ady in trays with sand for 10 or 20 days depenRaul da Silva of the Cerrado Center, Dr. ding on the variety. After the seed was deClibas Viera of the Universidade Federale de tached, seedlings selected for uniformity Vigosa and Dr. Charles A. Francis and James were transferred to the flowing solution M. Spain of CIAT in Colombia. The report culture with a flow rate of about 70 liters/ covers the greenhouse studies with corn, pot/hour and were grown for seven days in
wheat and bean varieties and the field stu- a complete Hoagland's solution without aludies with wheat and bean varieties. minum and with a low phosphorus concenGreenhouse Studies with Corn and Wheat: tration of 0.05 ppm P. After the harvest of
Methodology. some of the seedlings, the rest of the plants
A flowing solution culture method was were grown for 10 additional days under developed for these studies. The equipment two levels of aluminum (0 and 8 ppm Al) consists of twelve independent units, each and two levels of phosphorus (0.05 and 0.2 with a 5 liter-storage tank provided with a ppm P). Plant tops and roots were harvested, small water pump which is connected dried at 70 degrees Centigrade for a minithrough plastic tubes to five 5-liter pots. mum of two days, weighed and ground to Each pot corresponds to one variety on pass a 200 mesh stainless steel screen and
which 6 to 20 plants are grown depending analyzed for aluminum, phosphorus, calcium
on the species. The flow path is shown in and magnesium. Figure 2.16. A factorial design was used with The parameters evaluated were: dry matfive varieties, two levels of aluminum and ter production of roots and tops, root two levels of phosphorus, replicated three length, relative growth rates, mean relative times. extension rates, and nutrient absorption and
The pH of the nutrient solution was translocation rates for aluminum, phosmaintained at 4.5, and the concentration of phorus, calcium and magnesium. At the date Al and P was measured and adjusted to the of this writing the nutrient analyses are not original levels every two days. Considering available. the large number of pots used in the experi- Growth Rates (GR), Mean Relative ments, the flow culture solution technique Growth Rates (RGR), and Mean Relative had the advantage of permitting to control Extension Rates (RER) were calculated by the pH, aluminum and phosphorus levels in the use of the following formulae: GR=W2nutrient solution every two days within an W-1/t2-t1 (mg/day) and RGR=1n W2-1n acceptable degree of precision in only Wl/t2-t1 x 100 (%/day), where W2 and W,




43
POT
NUTRIENT SOLUTION POT
LEVEL
OUTLET
POT
INLET
INLET OUTLET
TUBE TUBE
POT
HEAD
TANK
POT
INLET INLET
VA HEAD
VA TANK
OUTLET
STORAGE TANK STORAGE TANK
WATER PUMP WATER PUMP
Figure 2.16 Flow path diagram for tolerance experiments in nutrient culture solution (Brasilia, 1975).-




44
are the top or root weights at time t2 and t1, (a Brazilian line) were most susceptible to respectively. RER=1n L2 In L1/t2-tl x phosphorus stress, attaining less than 33% of
100 (% day), where L2 and L1 are the root the maximum top growth rate. Among the lengths at time t2 and tl, respectively, wheat varieties the Brazilian ones were as a
The results are presented in Tables 2.11 group more tolerant to phosphorus stress and 2.12 and discussed in terms of their tol- than the Mexican varieties. The Brazilian erance to stress factors by comparing indi- varieties, with the exception of IAC-5, provididual treatment pairs: duced more than 50% of the maximum top
Treatment Al P Stress growth rate, while the Mexican varieties pro---ppm--- duced less than 50%. The Brazilian varieties
1 0 0.20 None IAS-20 and BH-1 146 were the most tolerant
2 0 0.05 P to phosphorus stress according to top
3 8 0.20 Al growth parameters.
4 8 0.05 Al + P Tolerance to Aluminum Stress Alone
Tolerance to Phosphorus Stress Alone (Treatments 3 vs. 1)
(Treatment 1 vs. 2) In general, most of the corn and wheat
When the corn and wheat varieties were varieties showed a greater reduction in root subjected to low available phosphorus (0.05 growth rates than in top growth rates in reppm P) in nutrient solution, absolute (GR) a sponse to high levels of aluminum in nuand relative growth rate (RGR) of roots and trient solution. This is the opposite of the tops, and mean relative extension rates situation when phosphorus was the limiting
(RER) of roots decreased in all varieties of factor. These results indicate that the main both species. Larger reductions were ob- effect of aluminum toxicity is the marked served in top growth rates than root growth reduction in root growth while the main efrates. These results suggest that the phos- fect of phosphorus deficiency is the reducphorus requirements for roots may be rela- tion in top growth. The reduction in root tively low compared with that for tops. Top growth rates and root length in the presence growth rate (GR) was the parameter which of aluminum was the criteria used to evalvaried the most among varieties. In corn, the uate aluminum tolerance. Brazilian varieties or hybrids Tuxpon-5243, Cargill-1 11, White Carimagua and
SA-30672, Agroceres-152 and Cargill-111 Catete-18267 corn lines were the lease affecproduced more than 50% of the maximum ted by high aluminum levels as compared to
top GR under phosphorus stress, while the control treatment. On the other hand,
DeKalb XL45-A (a U. S. hybrid), White Cari- Yellow Carimagua, DeKalb KL-45A and magua (a Colombian line) and Catete-18267 Tuxpon-52453 were the most sensitive. It




45
!iH 114G SONORA 633
0 ppm Al. 8 ppm Al. 0 ppm Al. 8 ppm Al.
Differential effects of aluminum and low phosphorus on root growth of wheat varieties. Left: BH-1 146, a tolerant variety. Right: Sonora-63, a susceptible variety. All roots were grown at the low phosphorus concentration (0.05 ppm P).




46
is also of interest to note that Catete-18267 Considering the difficulty of obtaining
and White Carimagua showed tolerance to seedlings of equal root length for all varialuminum stress but not to phosphorus eties, due to the inherent genetic differences,
stress. The opposite response was observed mean relative extension rate (RER) of roots with Tuxpon-52453. These characteristics appears to be a good parameter of evaluating
should be of interest to plant breeders, sug- aluminum tolerance since RER removes inigesting the possibility of crossing to provide tial root length differences. Moreover, exa dual tolerance to both aluminum toxicity pressing the rates in relative units (%) as a and low available phosphorus. function of the maximum rates attained
The varietal differences in wheat essen- without phosphorus or aluminum stress protially followed those observed when phos- vides a promising test for identifying varietal
phorus stress was the limiting factor. The differences. Brazilian varieties BH-1146, IAC-5 and According to mean relative extension
Toropi were the most aluminum tolerant rates, the ranking in aluminum tolerance
varieties, while the Mexican varieties (from the least to the most tolerant) for the INIA-66, Paraguai-214, CIANO and corn inbred lines was: SA-30672 > CateteSonora-63 were the most sensitive. Thus, the 18267 > White Carimagua > Catete-28150> wheat varieties sensitive to aluminum stress Yellow Carimagua > Palha Roxa-15768> were also sensitive to phosphorus stress, and Tuxpon-52453. In the hybrid corn lines the those tolerant to one were tolerant to the ranking was: Cargill-Ill > Agroceres-259> other. DeKalb-XL-45A > Agroceres-152. However,
A visual characteristic of the sensitive the hybrid corn lines had smaller differences corn and wheat varieties growth with 8 ppm in RER's among them than inbred corn Al was that their roots became stubby, thick lines. and brown. The lateral roots which initiated In general, the mean relative extension
during the first 7-day period in nutrient solu- rates of roots in all the wheat varieties detion without aluminum did not elongate creased more than 50% when aluminum was
when exposed to 8 ppm Al. The leaves added to the nutrient solution. However,
showed the phosphorus deficiency symp- varietal differences were noted since this
toms which normally accompany aluminum parameter fluctuated between 51% and 83%.
toxicity. In corn, the leaves of sensitive lines BH-1146, IAS-55 and Toropi showed the were deep purplish-red in color and the sen- smallest reduction and Sonora-63 and Amasitive wheat varieties developed a purple zonas had the largest reduction.
coloration in stems and leaves and after that Tolerance to Combined Aluminum and a yellowing of leaf tips. Phosphorus Stress (Treatments 4 vs. 1).




Table 2.11 Effects of phosphorus and/or aluminum stress in culture solution on growth rates (GR) mean
relative growth rates (RER) of corn tops and roots and the mean relative root extension rate
(RER). Expressed as percent of values attained by the treatment without any stress.
Corn Varieties P Stress Al Stress Al and P Stress
or Top Root Top Root Top Root
hybrids GR RGR GR RGR RER GR RGR GR RGR RER GR RGR GR RGR RER
----------------------------- % of unstressed treatment-------------------------------DeKalb XL-45A 29 40 44 52 97 57 67 34 42 52 29 39 34 42 34
Catete-18267 33 51 63 78 86 54 71 52 71 53 24 40 35 55 32
White Carimagua 38 47 49 60 58 60 69 51 61 51 33 42 33 43 31
Yellow Carimagua 41 53 57 68 49 37 49 42 53 47 32 44 31 42 43
Agroceres-259 42 58 61 73 75 51 65 49 63 53 18 29 13 22 23
Palha Roxa-15768 45 61 58 73 74 34 49 40 59 38 17 28 15 25 23
Catete-28150 45 62 72 80 93 23 39 62 72 49 15 28 31 42 17
Agroceres-152 52 64 70 79 59 49 61 40 52 43 29 41 28 40 27
Cargill-111 54 63 80 86 60 61 70 55 67 58 30 40 24 35 28
SA-30672 63 74 66 79 85 55 68 31 49 56 32 45 14 26 13
Tuxpon-52453 67 77 78 85 80 46 59 48 59 15 35 48 19 27 9




48
In Treatment 4, phosphorus was low These preliminary results have shown
(0.5 ppm P) and aluminum concentration some varietal differences in important
high (8 ppm Al). All the growth parameters growth characteristics among corn and evaluated in corn and wheat varieties were wheat varieties. When nutrient absorption reduced by more than 50% in the presence and translocation rate data (P, Al, Ca and of the combined stress when compared to Mg) are completed in 1976 a much more
the control treatment in which neither of complete interpretation will be possible. these two elements were limiting. In spite of Greenhouse Studies with Beans this considerable reduction, there was a In the case of beans, due to the conrange of tolerance within corn and wheat siderable number of varieties and unknown
varieties. to aluminum, the methodology was modiWithin inbred corn lines, the compar- fied for the initial screening. A factorial deison between the inbreds Tuxpon-52453 and sign using 10 bean varieties and two levels Catete-18267 is of interest. Catete-18267 of aluminum was replicated three times. had a larger reduction in top RGR than in Selected bean seedlings without attached root RGR and RER compared with Tuxpon- cotyledons were transferred to the flowing
52453 which showed the opposite response. solution culture and were grown for 15 days Probably this type of response is due to the under two levels of aluminum (2 and 8 ppm different performance of both inbreds under Al) and one level of phosphorus (0.05 ppm conditions of critical aluminum and low P). Consequently, the screening compared
available phosphorus in the growth medium. the presence or absence of aluminum stress The inbred SA-30672 seems to present a re- both in the presence of phosphorus stress. sponse similar to Tuxpon-52153. Palha Except for this change, the methodology
Roxa-15768 and Catete-28150 were the was the same as used in the corn and wheat
most sensitive inbreds to both high alu- experiments. minum and low phosphorus conditions. The results are shown in Table 2.13. In
Within the hybrid corn lines, the exception order to remove the effect of inherent was Agroceres-259 which showed the largest growth characteristics between varieties, the reduction in all the parameters considered in data for the 8 ppm Al treatment were exthis dual tolerance evaluation, pressed as percentage of those for the 2 ppm
The wheat varieties which maintained Al treatment. These relative yield indexes the best overall top and root growth rates were used to calculate the correlation coeffiand RER of roots in the presence of high cients of greenhouse and field parameters.
aluminum and low phosphorus in nutrient Relative yields of both tops and roots
solution were BH-1 146, IAC-5 and Toropi. reflected a wide range in tolerance to alu-




Table 2.12 Effect of phosphorus and/or aluminum stress in culture solution growth rates (GR), growth rates
(RGR) of wheat tops and roots and on mean relative root extension rates (RER). Expressed as
percentage of values attained by the treatment without stress.
P Stress Al Stress Al and P Stress
Top Root Top Root Top Root
Wheat Varieties GR RGR GR RGR RER GR RGR GR RGR RER GR RGR GR RGR RER
-----------------------------% of unstressed treatments-------------------------Mexican:
Paraguai-215 49 55 57 61 37 43 40 40 44 33 23 27 26 30 24
Sonora-63 42 50 50 55 47 39 47 34 40 21 33 41 29 34 21
INIA-66 40 48 45 54 50 37 45 23 30 42 32 40 19 25 26
CIANO 40 46 54 62 47 35 41 33 41 31 23 28 17 23 24
Ecuadorian:
Amazonas 43 49 66 71 45 37 44 33 38 17 15 18 25 30 28
Brazilian:
IAS-20 59 66 75 81 51 40 48 39 48 36 13 17 13 18 27
IAS-55 53 61 57 60 61 40 48 29 34 48 28 36 11 13 36
Toropi 51 58 67 75 61 55 62 54 63 45 45 53 37 47 37
BH-1146 64 71 79 86 54 55 62 48 56 43 43 51 41 49 40
IAC-5 48 59 86 89 59 46 57 41 49 31 41 52 40 48 39
-01




50
Table 2.13 Response of 18 Phaseolus vulgaris varieties grown in nutrient
solution containing high and low aluminum concentrations and
at a uniformly low level of available phosphorus. Mean of
three replications. Brasilia, 1975 dry season.
Top Yield Root Yield Root Length ,
Variety 2ppm 8ppm RTY1/ 2ppm 8ppm RRY./ 2ppm 8ppm RRLY
mg/plant % mg/plant % --- cm --- %
Diacol Nutibara-235 484 176 36 125 52 42 146 77 53
Caraota-260 504 191 38 305 207 67 148 50 34
Blue Lake 477 193 40 306 242 79 131 78 59
Manteigao FoscoNI-11 313 155 49 219 129 59 137 79 57
Tocantins-1222 238 132 55 363 197 53 136 79 58
897-S-182-N 329 196 59 150 119 79 112 83 74
Rico-23 274 179 65 190 148 77 110 82 74
Pretoredondao-242 687 452 66 331 245 74 94 59 63
Manteigao preto 625 430 68 263 193 73 140 88 62
1032-Col-1-63-A 361 264 73 192 172 89 133 88 66
Jalo-251 429 315 73 287 175 61 118 92 78
Selegao Cuba-1002 316 272 86 101 78 77 97 76 78
VI-1010 333 262 78 170 106 62 146 112 76
Ricobaio-1014 392 266 68 131 102 78 162 106 65
Costa Rica-890-37R 397 304 77 208 161 77 103 74 72
Costa Rica-1031 470 399 85 248 206 82 104 85 81
Ricopardo-896 450 358 79 188 176 93 107 89 83
Carioca-1030 354 315 89 217 193 89 95 83 87
/RTY = Relative Top Yield = (8 ppm Al/2 ppm Al) x 100. 2/RRY = Relative Root Yield = (8 ppm A1/2 ppm Al) x 100. 3/RRL = Relative root Length = (8 ppm Al/2 ppm Al) x 100.




51
Above: Varietal differences in top growth of beans under high levels of aluminum (8 ppm Al) and low levels of phosphorus (.05 ppm P). From left to right: Ricopardo-896 (a tolerant variety), Caraota-260 (a susceptible variety). Below: Root response to high Al levels in the susceptible bean variety (Diacol Nutibara-235). Left: 8 ppm Al, right 2 ppm AI.




52
minum toxicity and phosphorus deficiency fected more severely than root yields when in nutrient solution. For example, relative phosphorus stress occurs and root length is top yields ranged from 36% for Diacol Nuti- reduced significantly when aluminum stress bara-235 to 98% for Carioca-1030. Relative occurs. Consequently, the use of these pararoot yields varied from 42% for Diacol Nuti- meters in the screening of bean varieties for bara-235 to 89% for Ricopardo-896 and rela- dual tolerance (aluminum toxicity and phostive root length index from 34% for Caraota- phorus deficiency) looks promising. 260 to 87% for Carioca-1030. Visual symp- Field Experiment toms of aluminum injury were noted in the The next step in this investigation inroots which became thickened, turned volved subjecting the varieties to phosphorus
brown, and lateral roots which did not elon- and aluminum stress in the field. A new field gate (see photo). This symptom is character- experiment was established during the 1975 istic of aluminum toxicity and was observed dry season where all the material tested in to be more severe in aluminum-sensitive the greenhouse could be evaluated at three
bean varieties such as Caraota-260, Diacol levels of phosphorus and three levels of aluNutibara-235, and Manteig~o Fosco NI-11 minum saturation. The properties of the
than in aluminum-tolerant bean varieties Dark Red Latosol used appear in Table
such as Carioca-1030, Ricopardo-896, and 2.14.
Costa Rica-1031. Figure 2.18 shows the aluminum neuThe relationships for the different para- tralization and phosphorus retention curves meters are shown in Figure 2.17. Correlation based on soil-lime incubation and phoscoefficients between the relative top, root phorus sorption isotherm studies carried out and root length indexes were r = 0.46 for on the surface soil. A factorial design with relative top yields with relative root yields, three lime levels (designed to provide 10%, r = 0.32 for relative root yields with relative 35% and 70% aluminum saturation) and root length index, and r = 0.64 for relative three phosphorus fertilizer levels (to provide top yields with relative root length index. 0.008, 0.02 and 0.05 ppm P in the soil soluWith the exception of the root yield-root tion) was used, replicated three times. The length index correlation, the other r values lime levels applied were 0.5, 1.5 and 4.0 were highly significant at the 1% level. These tons/ha of CaCO3-equivalent. The phosresults suggest that the best parameters for phorus rates needed to achieve the desired evaluating bean tolerance to aluminum toxi- levels in the soil solution were 160, 778 and city and phosphorus deficiency in nutrient 1374 kg P205/ha as triple superphosphate solution are the top yields and the root broadcast and incorporated into the topsoil.
length, probably because top yields are af- The lime was applied to the field and incor-




53
Table 2.14 Chemical characteristics of the Dark Red Latosol site at CPAC used for the tolerance experiment. Mean of nine replications.
Soil pH Available P Exchangeable
Depth H20 1:I IN KC1 (NC extractant) AI Ca + Mg ECEC Al Sat.
-- cm -- ----ppm---- --- meq/100cc --- %
0-20 4.7 3.9 1.9 1.04 0.15 1.19 87.8
20-40 4.6 3.9 1.5 0.90 0.15 1.05 84.8
9@ 600
80 -6.0
500
70 A 0.
c ~Alo ..
60 / 5.5 E40050- s,
a / pH
5o _0 300
40- 5.*- I
-- 0 o o0
30/ 0 200
20' -4.5
100
10
O -4.0 0
0.55 1.64 4.37 0 .008 .02 .05 .1 I 2
Dolomitic Lime (tons/ha) P in Soil Solution (ppm)
Figure 2.18 Aluminum neutralization and phosphorus retention curves of
the Dark Red Latosol soil (10-20 cm layer).




54
porated to 20 cm depth on March 20, 1975. aluminum stress alone (0.05 ppm P and 61% A detailed sampling of soil was done at one, Al saturation). Although grain yield data resix and ten months after incorporation and ported on a row basis cannot be directly standard analyses were made to evaluate the interpreted in terms of tons/ha because of soil-lime reaction during the dry and wet sea- border effects, the maximum yields of each sons. variety were equivalent to a range from 1.3
During the 1975 dry season the 10 to 3.5 tons/ha, which is normal. The range
wheat varieties and the 18 bean varieties tes- of yields observed between wheat varieties ted in the screenhouse were planted in indi- was thirty-ninefold under both phosphorus vidual 6 m rows. Also 26 sorghum lines not and aluminum stress, about sevenfold under previously tested in the greenhouse were aluminum stress alone, fivefold under phosplanted to take advantage of the available phorus stress alone, and about twofold with space. The sorghum results will be reported no stress. This illustrated the wide varietal next year to accompany the greenhouse differences in tolerance to the combinations
data. Corn was planted during the of high levels of aluminum and low available
1976 rainy season and will be reported in phosphorus, the two main adverse soil condithe 1976 Annual Report. The experiment tions characteristic of this Dark Red Latowas planted on May 26, 1975. Beans were sol.
harvested on August 29 and wheat on Sep- Of the ten wheat varieties tested at the
tember 5 and 22, depending on the variety, lowest lime-P levels, IAC-5, BH-1146, and A blanket broadcast application of 100 kg Toropi showed most tolerance. They showed K20/ha as KCI, 10 kg Zn/ha, 10 kg borax/ha a better stand and produced significantly and 0.5 kg Na2MoO4/ha was applied. Nitro- higher grain yields than the other wheat varigen was applied according to the crop: eties. The most sensitive varieties under both
wheat 80 kg N/ha in two applications and adverse soil conditions were Sonora-63, Parabeans 60 kg N/ha also in two applications. guai-214, and INIA-66 with grain yields less Wheat than 10% of their maximum yields. These
The performance of the 10 wheat vari- sensitive varieties showed phosphorus defieties is reported on Table 2.15. All varieties ciency symptoms in stems and leaves during responded strongly to phosphorus and lime early growth and after that a yellowing and application but showed marked differences necrosis in the leaf tips. particularly under both phosphorus and All wheat varieties showed a significant
aluminum stress (0.008 ppm P and 61% Al yield response to phosphorus at all lime
saturation), phosphorus stress alone (0.008 rates. Maximum yields were obtained at the ppm P and 24% Al saturation) and under highest phosphorus rate although at differ-




Table 2.15 Field performance of various wheat varieties at different levels of phosphorus (160, 778 and
1374 kg P205/ha*)and aluminum saturation. Brasilia 1975 dry season (irrigated). Mean of
three repT ications.
Lime: 0.5 tons/ha 1.5 tons/ha 4.0 tons/ha
Wheat 67% Al saturation 46% Al saturation 24% Al saturation
varieties 160 778 1374 160 778 1374 160 778 1374
------------------------------Grain yields (g/4m row) ------------------------Mexican:
Paraguai-214 4 26 83 26 109 196 37 150 170
Sonora-63 14 67 148 31 216 265 152 249 170
INIA-66 14 36 50 71 76 96 76 123 160
CIANO 59 117 175 ill 185 190 88 134 229
Ecuadorian:
Amazonas 78 206 227 166 308 265 153 263 356
Brazilian:
IAS-20 49 174 150 140 199 261 114 243 258
IAS-55 76 237 288 188 323 424 116 387 399
Toropi 116 243 245 255 377 409 146 256 416
BH-1146 132 216 311 147 289 323 180 244 259
IAC-5 157 326 357 143 248 317 179 195 251
01
*Equivalent to a soil solution level of 0.008, 0.02 and 0.05 ppm P, respectively.




56
ent levels of liming. Maximum yield was ob- conditions. Figures 2.19 and 2.20 show this gained with IAC-5 at the lowest lime rate trend expressed as the mean of the four
(0.5 tons/ha), Sonora-63, BH-1146, Para- Mexican varieties and the five Brazilian variguai-214, IAS-55, and IAS-20 at 1.5 tons/ eties. Nevertheless, these appear to be imporha, and finally Ciano, Amazonas, INIA-66 tant differences between varieties of the
and Toropi at the highest lime rate (4 tons/ same origin. Among Brazilian varieties, the ha). two developed closest to the Cerrado, IAC-5
Varietal differences also were noted in Campinas, and Bh-1146 in Belo Horizonte
with respect to phosphorus response. While were more tolerant to the stress factors than
BH-1 146 and IAC-5 produced nearly half of those developed in Rio Grande do Sul (IAStheir maximum yields with the lowest broad- 20 and IAS-55) where the soils, although cast rate (160 kg P205/ha), Sonora-63, Para- acid, are more fertile than in the Cerrado. guai-214, and INIA-66 produced only a Variability is also observed among the Mexitenth of their maximum production at that can varieties. Figure 2.21 shows an example
rate. Both BH-1146 and IAC-5 were devel- of this variability. These results suggest good
oped in the periphery of the Cerrado, in possibilities of breeding the tolerance to aluMinas Gerais and Sg'o Paulo, respectively. minum and phosphorus stress of Brazilian
From the results it was also possible to varieties with the short-statured, lodging renote that the most tolerant wheat varieties sistance properties of the Mexican varieties. (IAC-5, BH-1146, and Toropi) had smaller Beans
yield increases to the first increment of lime The results of the bean field data are than the sensitive varieties and showed a shown in Table 2.16. All 18 varieties resharp yield decrease at the highest lime rate sponded positively to both lime and phos(4 tons lime/ha). On the other hand, the phorus applications, although the larger
most sensitive varieties such as Sonora-63, yield increases (more than 50%) were obParaguai-214, and INIA-66 showed a positive served in response to phosphorus than in reresponse to all increments of lime. None of sponse to liming (less than 30%). In general, the Brazilian varieties appeared to be sensi- the maximum grain yields of all varieties are tive to aluminum stress. high. If extrapolated on a per hectare basis,
The general trend shows that varieties they range from 2.8 to 4.7 tons per hectare; bred in Brazil exhibit greater tolerance to but these figures include border effects. both stress factors than varieties bred in Several bean varieties were found tolMexico. Brazilian varieties were generally se- erant to both phosphorus and aluminum lected in acid soil conditions while the Mex- stress. The most tolerant were Carioca-1030, ican ones were selected under calcareous soil Ricopardo-896, Costa Rica-1031, Costa Rica-




400
S160 kg P2O/ha 778 kg P205/ha 1374 kg P205/ha
2 (3ppm avail. P) (7.4 ppm avail. P)
200
E 300 Brazillio
200 Brazilian .o------- J/d, Mexican
Z s *.,o Mexican
_ Mexican/ os
100--E c: 0/ o-' ....Mexican o a (16.8 ppm avail. P)
S I I I I
0 0.5 1.5 4.0 0.5 1.5 4.0 0.5 1.5 4.0
Lime Added (tons Ca Co3 equiv. /ha)
II I II InI
61 46 24 61 46 24 61 46 24
% Al Saturation
Figure 2.19 Differential performance of wheat varieties at various levels of aluminum as a function of phosphorus under field conditions in Brasilia. Mean of five Brazilian varieties and four Mexican varieties with three replications each. 1975 dry season.
01




500 Lime: 0.5 tons/ha Lime: 1.5 tons/ha Lime: 4.0 tons/ha
(61 % AI Satn.) (46% Al Satn.) (24% AI Satn.)
0 400- IAS-55 /400 IAC-5 (Brazilian / / IAS-55
E ,A-/
3" IAC- 5
300 / IA-- IAC-5
/ /
/// ~(Brazilian) / S
200- / /Sonora 63
SSonora 63
.5 100 / (Mexican) INIA 66 A INIA 66
o /7
Mexican)
I I I I I I I
160 778 1374 160 778 1374 160 778 1374
P Applied (kg P205/ha)
I I I I I I I I
0.008 0.02 0.05 0.008 0.02 0.05 0008 0.02 005
P in Solution (ppmrn )
I I I I I II I I
2.8 8.1 18.4 3.2 72 16.0 2.8 7.0 16.0
Available P N.C. Extraction (ppm)
Figure 2.20 Comparison between two Brazilian varieties (TA-C-5 and IAS-55) and two Mexican varieties (INIA 66 and Sonora 63) to show variability in response to aluminum and phosphorus stress under field conditions. Brasilia 1975 dry season.




S 400 Lime: 0.5 ton / ha Lime: 1.5 tons/ha Lime: 4.5 tons / ha
o (61 % Al Satn.) (46 % Al Satn.) (24 % Al Satn.)
E
300
Brazilian Brazilian Brazilian
U)
200
-///0,0 0~ y '
Z
. 100 MMexican Mo Mexican
I I I I I I I
S160 778 1374 160 778 1374 160 778 1374
P Applied (kg P205/ha)
I I I I I I I
Q008 0.02 0.05 0.008 0.02 0.05 0.008 0.02 0.05
P in Solution (ppm)
I I I I I I I I I
2.8 8.1 18.4 3.2 7.2 16.0 2.8 7.0 16.0
Available P N.C. Extraction (ppm)
Figure 2.21 Differential performance of wheat varieties at various levels of phosphorus
as a function of aluminum saturation under field conditions in Brasilia. Mean of five Brazilian varieties and four Mexican varieties with three replications each. 1975 dry season.




60
Al and P stresses (61% Al sat., 3 ppm avail. P) P stress only (24% Al sat., 3 ppm avail. P)
Wheat-varietal differences in tolerance to aluminum and phosphorus stress. On the left furrow, two Mexican varieties (Sonora-63, Ciano); on the right furrow, two Brazilian varieties (IAC-5, BH-1 146).
Al stress only (24% Al sat., 17 ppm avail. P) No Al or P stress (24% Al sat., 17 ppm avail. P)




61
890-37R and Ricobaio-1014, which reached lime for all phosphorus rates (Figure 2.23).
yields greater than 50% over the most sensi- A comparison of grain yields of the two crop tive varieties at the low phosphorus, high species on the basis of their relative yields
aluminum stress treatment (0.008 ppm P (% of maximum) shows that wheat had
and 61% Al saturation). The most sensitive higher grain production than beans at the
varieties were Diacol Nutibara-235, Caraota- intermediate level of lime and showed no 260, Blue Lake-141 and Manteigao Fosco further yield increases with an additional
N1-11. Table 2.16 shows no relationship be- lime. This indicates that lime requirements tween country of origin or seed coat color for beans are higher than those for wheat,
with tolerance to aluminum or phosphorus and suggest a lower aluminum tolerance in
stress. beans than in wheat.
Bean yields of the tolerant varieties With respect to phosphorus response,
were higher than the sensitive varieties at all the aluminum-tolerant and aluminum-senphosphorus and lime rates. However, when sitive bean varieties also showed similar tolthese yields were expressed as a percent of erance or susceptibility to low available their maximum yields, important varietal phosphorus. Differences among wheat and differences were only noted at the two beans also were noted. Figure 2.22 illustrates
lowest lime rates (61 and 46% Al saturation) the positive response of both crop species as with the lowest phosphorus rate (160 kg phosphorus rates increased and also shows
P205/ha). In response to liming, sensitive species differences at the lowest broadcast
bean varieties showed higher grain yield in- phosphorus application (160 kg P205/ha). creases (about 50%) than tolerant varieties Wheat showed a higher percentage of maxifor each increment of lime at the lowest mum yield than beans at all lime rates. For
phosphorus rate. These results show the evi- example, at the 1.5 and 4 tons lime/ha dent varietal differences among beans under levels, wheat produced 50% of its maximum both adverse soil conditions and also that yield with the lowest phosphorus rate. On
when aluminum is neutralized and available the other hand, beans at the same limephorphorus is increased the differences tend phosphorus combination produced only 22 to disappear. and 34% of their maximum yield, respecAll bean varieties showed a positive tively.
yield increase for each increment of lime ex- These preliminary results indicate that
cept at the highest lime-P combination. This wheat, in addition to tolerating aluminum, is a different type of response than that of presents a better response to low available wheat varieties where essentially the yield phosphorus than beans. A more detailed response was only to the first increment of analysis, taking into consideration other pa-




Table 2.16 Bean grain yields at different levels of phosphorus and aluminum saturation in the field.
Mean of three replications. Brasilia, 1975 dry season (irrigated).
Seed 0.5 tons/hal/ 1.5 tons/ha 4.0 tons/ha
coat 61% Al sat. 46% Al sat. 24% Al sat.
Bean varieties Origin* color 160 778 1374_/ 160 778 1374 160 778 1374
---------------------- g/4m rows-----------------------Diacol Nutibara-235 BR Pinto 27 199 278 38 196 271 69 277 286
Caraota-260 VZ Black 49 207 230 70 222 300 134 323 293
Blue Lake-141 US White 34 275 336 69 317 358 89 265 296
Manteigao Fosco NI-11 BR Black 35 225 288 64 278 350 123 238 312
Tocantins-1222 BR Black 55 171 303 79 224 332 106 252 358
897-S-182-N BR Black 77 245 482 101 417 517 163 427 566
Rico-23 BR Black 38 378 479 84 366 469 188 365 475
Preto redondao-242 BR Black 62 289 399 62 327 469 151 353 392
Manteigao preto BR Black 69 170 328 90 277 425 163 310 416
1032-Col-1-63-A BR Brown 55 302 445 110 363 393 137 370 395
Jalo-251 BR Red 52 160 363 72 250 407 151 213 341
Selegao Cuba-1002 CB Black 69 203 404 104 341 462 209 426 453
VI-1010 BR Red 78 251 371 85 338 443 163 417 446
Ricobaio-1014 BR Red 83 279 406 109 381 413 144 422 456
Costa Rica 890-37R CR Red 83 392 457 130 406 515 217 469 503
Costa Rica-1031 CR Black 90 356 381 122 402 493 167 498 496
Ricopardo-896 BR Brown 124 342 464 133 404 501 205 486 563
Carioca-1030 BR Pinto 151 391 432 152 401 489 169 522 530
*BR=Brazil, VZ=Venezuela, U.S.=United States, CR=Costa Rica, CB=Cuba. i/Lime 2/kg P205/ha




3
o 600
E 0.5 tons time / ha 1.5 tons lime/ha 4.0 tons lim /hq__500 (61 % AI Satn) (46% Al Satn) (24% Al Carloca
4 A -0 - .- Satn) / 1030
a 400 >*a"Crioca-IO30
CA s Coariocam1030 -Carloco -1030
S300- / # 0/ /
Caraota-260
- 200 Caraoto- 260 1 Caraota- 260
100
C I I I I I I I I
o 0 160 778 1374 160 778 1374 160 778 1374
P Applied (kg P205/ha)
S I I I I I I I I I I
0.008 0.02 0.05 0.008 0.02 0.05 0.008 0.02 0.05
P in Solution (ppm)
i I I I I I I I I I I I
I 2.8 8.1 18.4 I 2.8 7.2 16.0 1.3 2.8 7.0 16.0
Available P-N.C. Extraction (ppm)
Figure 2.22 Differential response of two bean varieties (Phaseolus vulgaris) at different levels of phosphorus and aluminum stress under field conditions. Mean of three replications. Brasilia 1975 dry season (irrigated).
C)




64
11 100 BE N
100 WHEAT BEANS
E
80
>- 6003
C 200
160 778 1374 160 778 1374
P Applied (kg P2O5/ha)
S0.5 tons/ha lime 160 kg P20s/ha
(61% AI Satn.) (3 ppm avail. P)
1.5 tons/ha lime 778 kg PA/ha
(46% Al Satn.) (7 ppm avail. P)
/ 4.0 tons/ha lime 1374 kg P2Os/ha
- (24% Al Satn.) (17ppm avail. P)
0100- ..
E
O
80
" 604
0
**, ::*.:
o --:
..-
20 .... "'"
0.5 1.5 4.0 0.5 1.5 4.0
Lime Applied (tons/ha)
Figure 2.23 Species differences in tolerance to phosphorus and aluminum
stress between wheat (left) and beans (right) grown at the
same time during the 1975 rainy season in Brasilia. Mean
of 10 wheat varieties and 18 bean varieties and time replications.




65
rameters, should provide additional informa- fective in predicting field performance when tion useful for selecting crop species and high aluminum saturation and low available varieties able to function well in these high phosphorus are the limiting factors in aluminum, phosphorus-deficient Oxisols. growth and grain yields. Further evaluations
Correlation Between Greenhouse and Field taking into consideration other important Data. growth and physiological parameters and
One of the objectives of these studies yields of other crops species will provide was to determine if varieties and species can additional information for better evaluating be selected for tolerance to aluminum and the advantages of using greenhouse tests as a low available phosphorus in greenhouse tests practical and economical screening method using nutrient solution culture. The green- in tolerance studies. house test was considered an important tool
because it greatly reduced the space and MANAGEMENT OF WATER STRESS time needed during the screening process as PERIODS compared to field tests. D. E. Bandy and R. B. Musgrave
The correlations between grain yield in Crop physiology studies were conthe field and several greenhouse parameters tinued during the year with the overall obare shown in Figures 2.24, 2.25 and 2.26 for jective of understanding the relationship bevarieties under both aluminum and phos- tween temporary drought stresses caused by phorus stress in the field and greenhouse. veranicos and soil fertility management. Two Figure 2.24 shows a very close relationship consecutive experiments continued to evalubetween wheat yields and mean relative root ate the effect of key soil management pracextension rates with an r rate of 0.93.** tices on water stress in corn. Two other conFigure 2.25 shows the correlation with other secutive experiments studied the potential growth parameters which was not as close as of mulching as a practice for attenuating the previous one but ranged in r values from drought stress. A fifth field experiment stu0.62** to 0.83. dies similar parameters on upland rice.
Among bean varieties, Figure 2.26 Soil Management Effects on Water Stress
shows very close correlations between field in Corn grain yields and relative top yields, root The field experiment initiated during
yields and root length under greenhouse con- the 1974 dry season was continued during ditions. the 1974-1975 rainy season and the 1975
These close relationships between dry season. The first crop results were hamgreenhouse and field observations suggest pered by the slow reaction of lime during that preliminary greenhouse screening is ef- the dry season and the abnormal phosphorus




66
200- WHEAT
EIO
A
A
100
A
S50- A
A Y= -91.30 + 149.54 X
a A&A rc0.93**
0 0.5 1.0 1.5 2.0
Mean Relative Root Extension Rate
(% /day)
Figure 2.24 Relationship between mean relative root extension
rates of wheat varieties measured in the greenhouse and grain yields in the field, both under aluminum
and phosphorus stress. Brasilia 1975 dry season.




WHEAT 67
200
ISOA A
3: 150oo
100 -= .6 066
A A
M~ A A A A
c 50 A Y=4.36+55.54X Y=3.76+106.68X
50
r = 0.69* r = 0.83~*
M& AA
A I I A
0 I 2 3 0 0.5 1.0 0.5
Growth Rate of Tops (%/day) Growth Rate of Roots (%/day)
A A
l 150S100 ,0
A A
50 A Y A 3.36+ 28.56X A Y=-II.35+41.84X
o" / / r=0.6 2* r =0.77**
0 1.5 3.0 4.5 o 1.5 3.0 4.5
RGR Tops (%/day) RGR Roots (%/day)
Figure 2.25 Correlation between growth rate parameters of wheat varieties measured in the greenhouse and wheat grain yields in the field, both under aluminum and phosphorus stress. Brasilia 1975 dry season.




BEANS
160- DA
A A A
o 120
E
V
80 A
A AA A
- 40 Ak
. Y=-26+ I.42 X Y=-44+ 1.54X Y-46+ I.66X
r=0.80* r= 0.70** r=0.70* *
I II I I I I I I I I I
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
Relative Top Yield (%) Relative Root Yield (%) Relative Root Length (%)
Figure 2.26 Relationship between greenhouse and field parameters measuring joint tolerance to aluminum and phosphorus stress in beans. Brasilia, 1975 dry season.




69
contents of the superphosphate applied early stressed plants. The results of both
(1974 Annual Report). These problems were plantings are discussed as follows. corrected in the two subsequent experiments Growth Analysis. as lime reacted properly and additional triple The growth of the unlimed treatsuperphosphate of known phosphorus com- ment was always inferior to the deep and
position was applied, shallow lime treatments. There were no
The rainy season experiment was significant growth differences between the
planted in December and was designed to deep and shallow lime treatments during
measure the effects of water stress on plants the early part of vegetative growth with as a result of a veranico under five different shallow incorporation at times giving better soil management treatments as follows: no growth. From about 50% tasseling on, deep lime, 8 tons/ha of lime incorporated into 15 liming usually showed significant increases cm depth, 8 tons/ha lime incorporated to 30 in leaf area, leaf dry weight, and total dry cm depth, 640 kg P205/ha broadcast, and weight. Figure 2.28 shows this effect for the
160 kg P20,5/ha banded. The lime treat- rainy season experiment. The better growth
ments received 400 kg P20,5/ha of broad- seems to be related to delayed leaf senescast and 100 kg P205/ha banded, and the cence.
P25treatments received 4 tons/ha lime in- Phosphorus applied in bands gave betcorporated to 15 cms. A blanket application ter seedling vigor than the broadcast appliof all other required nutrients was given to cation because the phosphorus band was all plots. more easily utilized by the young corn root
There were no major changes in plan- system. After the seedling stage, the broadning and execution of the 1975 dry season cast treatments gave significantly superior experiment from the previous two experi- growth for the first two crops. The amount ments. The experiment was planted on June of phosphorus applied in the bands was not 2, 1975 and was harvested 164 days later, sufficient to maintain optimum plant growth Two veranicos were simulated by with- as Figure 2.28 shows. During the third conholding irrigation water. The first veranico secutive crop, however, plants in the banded (early stress period) occurred during the treatments were able to grow at the same rapid stage of vegetative growth, 63 to 80 rate as those in the broadcast treatment bedays after planting. The late stress period cause of the reapplication of phosphorus in commenced 100 days after planting and bands for each crop and the diminishing relasted for 10 days. Fifty percent tasseling sidual effect of the only broadcast applicawas obtained 98 days after planting for the tion. non-stressed plants and 100-104 days for the




70 Veronica
O No Lime
O Shallow Lime
4- 0 Deep Lime
4\
3
,
50% \\,..,
2- ~~Tassel I .
01
S5
-- Broadcast P Veranico
o 0 Banded P
a, '
4-4
-J 3-,
2 50% .7
Tassel
- T
jL..
20 30 40 50 60 70 80 90 100 ,,C
Days After Planting
Figure 2.28 Effects of water stress and fertility treatments on the leaf
area index of corn during the 1974-1975 rainy season. Solid lines are treatments where no water stress occurred. Dashed lines are the treatments subject to the veranico. Bars are
LSD.o5.




71
Water stress during the vegetative temperatures were found to fluctuate daily
growth stage produced significant decreases down to a 60 cm depth, as Figure 2.30
in all growth parameters. The plants did not shows. The upper soil layer was cooler at recover from the effects of the water stress night by 5 degrees Centigrade or more than period during the vegetative stage in the deeper soil depths which could cause the up1975 dry season crop as the measurements ward movement of water due to the assofor leaf area (Figure 2.29), leaf dry weight ciated vapor pressure gradient. Soil temperand plant height, indicate. Other growth atures during the two simulated veranicos
parameters, such as stem dry weight, were reflect the air temperature differences as the
not permanently affected. Fertility treat- season progresses. September soil temperaments usually did not produce differences in tures averaged 6 degrees Centigrade warmer the initial water stress effect, but deep lim- than August's soil temperatures. ing and broadcast-P plants recovered from Soil Water Use.
some of the stress effects earlier than the Soil water use was shown to be inother treatments. Water stress after tasseling fluenced by depth of lime incorporation for enhanced leaf senescence and reduced leaf all three experiments. Water use during the
dry weight, stem dry weight, ear dry weight, early stress period usually did not show a and tassel dry weight. Net assimilation rates large deep lime effect. Late stress periods (NAR) and relative growth rates (RG R) were widened the differences between the nureduced by the early stress period but did trient treatments with the deep lime treatnot show a late stress effect. No significant ment always showing the greater soil water differences between the five fertility treat- use, especially below the 22.5 cm soil depth. ments were seen for NA R and RG R. Deep-limed plants used anywhere from 2 to
Soil Temperature 18 mm more soil water than the other treatThe dry season is not only without ments. Table 2.17 shows that soil water exrainfall but it is also the coldest season of traction was influenced by lime rates, depth the year with May through August night of lime incorporation and method of phostemperatures averaging 4 to 5 degrees Centi- phorus application. grade lower than the rest of the year. Night For a proper study of soil-plant water
temperatures for 1975 were quite cool in use it was necessary to get an understanding
June and July, averaging 13 and 12 degrees of the amount of soil water used by a corn
Centigrade, respectively. The coolest night crop grown under well-watered conditions was 4 degrees Centigrade. The cool nights re- and under veranico conditions where the sulted in low soil temperatures which were water contents become very limiting. The
not conducive to optimum corn growth. Soil 26th of February, 1975 was the last day of a




72
4.0
Shallow Lime
-- No Stress
--Early Stress
3.0 ....Late Stress
2.5 / \
2.0
1.5
1.0 -1.05 1.05 1.05 1.05 .05
0.5
0
S3.5 Deep Lime
._1 2.5-/
20
1.5
10 .05 1.05 1.05 1.05
0
24 34 44 54 64 74 84 94 104 114 124 Days After Planting
Figure 2.29 The effect of plant water deficit on corn leaf area index.
1975 dry season.




0
22
22 5cm
2- 18 cm
eL 14
1 I 1I I I I I I I I I 1 I
1016 24 6 16 26 5 15 25 4 14 24 4 14 24 3
June July August Sept. Oct. Nov.19
Figure 2.30 Soil temperature profile of uncropped Dark Red Latosol in Brasilia during the late dry season and early rainy season of 1975.
C,,




Table 2.17. Comparison of the amount of soil water unused by the corn plant in relation to the deep
liming treatment during the stress periods for three growing seasons.
O-Lime Shallow Lime Deep Lime Broadcast-P Banded-P
Early Late Early Late Early Late Early Late Early Late
Crop Stress Stress Stress Stress Stress Stress Stress Stress Stress Stress
------------------------------------ -mm H20 -- --------------------------1974 Dry 4.4 5.0 4.2 4.1 0 0 5.2 1.5 7.2 8.8
1974-75 Rainy l/ 5.1 2.1 0 0 2.0 6.2
1975 Dry 8.4 18.6 1.5 6.7 0 0 6.2 5.8 4.0 11.8
Mean 6.4 9.6 2.9 4.3 0 0 5.7 3.1 5.6 8.9
No early stress during this season.




75
4-day 96.3 mm rain. Soil water measure- ishes as the soil dries out. The 45 cm soil ments began two days later to determine soil layer supplied very little water at first, water use by corn in relation to five fertility but it was supplying over 20% of the availmanagement practices. The results are shown able water within five days after irrigation. in Table 2.18. Plant Water Status.
Over the same 5-day period soil water The various soil management practices
lost from a bare soil, with no vegetative influenced plant water stress with deep growth (0-45 cm soil profile), to surface eva- limed plants usually showing less stress in poration and drainage amounted to 3.10 comparison to the other four treatments.
mm. Soil water contents in the same bare Deep limed plants became water stressed
soil area for 12 days of the 18-day veranico later on in the day and returned to less negaare shown in Figure 2.31. The top 22.5 cm tive leaf water potentials earlier in the evendried out at the rate of 1.53 mm per day. A ing. For example, during the 1974-1975 wet 5-day comparison (Table 2.19) was made be- season veranico, shallow limed plants reach tween the ET rates from stressed and non- a leaf water potential of -20 bars four days
stressed plants during the veranico to deter- earlier than deep limed plants (Figure 2.32). mine the respective ET rates or amount of In other stress periods, deep limed plants
soil water used per day. never became severely stressed while the
Soil water contents were measured in shallow limed plants were near the permathe early morning and late afternoon to nent wilting point. Banded P plants were less
study the daily water flux and extraction stressed during the first two experiments bepatterns. In four days under optimum soil cause they were much smaller plants. When
water conditions the corn plants used 47.7% the corn plants were equal in size for the of the total available water in the 0-45 cm two phosphorus application treatments, the soil profile. The average soil water tension broadcast P treatment was superior, i.e., after four days was 37.75 centibars. The 30 lower leaf water potential and higher relative cm soil depth always showed that soil water water contents (Figure 2.33). was used during the night. The reason was Stomatal resistance (Rs) and transpiraprobably related to the water extraction pat- tion rate (E) results always showed that deep tern for the corn plants as shown in Table lime incorporation delayed and reduced 2.20. The extraction pattern was a dynamic plant water stress. Diurnal measurements process, changing daily as the soil dries out. showed that stomates were closing in the For example, the 0-15 cm soil layer supplied late morning for shallow limed plants as the more than half of the water used during the veranico became more severe. The stomates first few days but its supplying power dimin- never closed in the late morning due to plant




76
Table 2.18. Average daily evapotranspiration rates over a 5-day period
for corn (Hanway stage 5-6) in relation to five fertility
management practices and LAI. (February 28- March 4, 75).
Treatment ET LAI
mm cm2/cm2
O-Lime 5.12 3.1
Lime-Shallow 6.44 4.2
Lime-Deep 6.16 4.1
Broadcast-P 4.67 3.9
Banded-P 5.07 3.6
Bare Soil 3.10 --Table 2.19. Evapotranspiration rates from stressed and non-stressed corn
plants during a veranico.
Date Stressed Non-stressed Bare Soil
---------------------- mm/day--------------------August 3 5.66 3.79
September 3 1.12 8.15
October 3 0.95 7.24
November 3 1.95 5.10
Mean 2.41 6.07 1.37




77
Soil Water Content (g/OOg)
18 20 22 24 26 28 30 32
15 11111 -20
25
E
0
30)
40
45
"14 '16 5 2 16 12 9 50 L Days After Last Rain
0
Figure 2.31 Decreasing soil water content under a bare soil during
14 days without rain. Brasilia 1974-1975 rainy season.




78
Table 2.20. Soil water extraction pattern for corn, 1-5 days after
irrigation.
Soil Depth (cm)
Date 0-15 15-22.5 22.5-30 30-45
------------------- % H 2 0 ------------------August 3 44.9 30.7 19.6 4.8
September 3 52.8 20.8 16.0 10.4
October 3 36.2 28.8 21.3 13.7
November 3 6.6 35.4 34.5 23.5
Mean 35.5 28.9 22.9 13.1
Measuring leaf area during water stress periods.




0 79
-21 Shallow Lime
-20
O
00
a -1 aDeep Lime
0
-18
- 16
0)
-15
-14
13 ,I I I I I I I
5 6 7 8 9 10 II 12
Days During Water Stress
Figure 2.32 Effect of depth of liming on the leaf water potential for
corn (third leaf from top) taken during a veranico
(February 27-March 17, 1975). Brasilia 1974-1975 rainy
season.




80
-21
-20
-19 Banded P18
0
Broadcast P 14
10 12 14 16 17 18 19
Days During Water Stress
Figure 2.33 Effect of phosphorus placement methods on the
leaf water potential of corn during a 17-day
water stress period. February 27-March 17,
1975. Brasilia 1974-1975 rainy season.




81
water stress in the deep lime treatment (Fig- grain formation stage decreased yields by ure 2.34). The transpiration rate (E) for 100-140 kg/ha/day.
plants in the deep limed plots was shown to With all other fertilizer treatments being
average 68% more than E for shallow limed equal, incorporation of lime 30 cm deep inplants during the 1974-1975 veranico (Table stead of the traditional 15 cm depth pro2.21). duced 1157 kg/ha more grain for the three
Other Effects. crops under non-water stressed conditions
Leaf temperatures generally agreed very and produced 2043 kg/ha more grain under
closely with stomatal resistance and trans- the stressed conditions. On a three crop averpiration results. Plants with the least Rs and age, late stress reduced yields by 19% for most E had the lowest leaf temperatures. deep limed treatments and 27% for shallow
This occurred in the deep limed plants. Corn limed treatments. canopy microclimate was usually influenced Broadcast application of phosphorus
by lime depth incorporation. Shallow limed gave less yield reduction in relation to plant
plant canopies showed lower percent relative water stress when compared to the banded humidities than deep limed plant canopies. application of phosphorus. Both treatments
Leaf chlorophyll contents were found to be showed significant reductions in grain yield
degraded with increasing plant water stress when water stress was imposed on the plants but no nutrient influence was noted. Photo- during the grain filling stage. synthetic rate measurements were taken on The effect of the late water stress period
one experiment only. The results showed on final grain yield was directly related to
that the deep limed plants averaged 10 mg photosynthate production and translocation
CO2 dm-2 hr-1 more than shallow limed to the ear. Stover dry weight decreased durplants during the stress period. ing the ear filling stage which suggests that
Grain Yield. photosynthate stored in the culm during the
At harvest, the deep lime incorporation vegetative stage was translocated to the ear.
plots outyielded shallow limed plots in both The results also suggest that the late water water stressed and non-water stressed treat- stress period (79-90 days after planting) ments. The overall results of the three crops slowed photosynthate production but inare shown in Table 2.22. Non-limed treat- creased photosynthate partitioning. Over
ments yielded less than limed plots. A 10-15 30% of the ear dry weight accumulation day water stress period during the vegetative occurring during the water stress period growth stage permanently reduced plant size came from photosynthate stored in the but it did not significantly reduce grain culm, whereas only 2.9% was translocated
yield. A 10-15 day stress period during the in the no water stress period treatment over




82
80 No Lime Days'
5
60 40
9
20 2
0
0
100- Shallow Lime
I 0
~60
040- 5
E9 09 .1-- 2
0
40 -Deep Lime5
2
20- 9
Time (hrs.)
Figure 2.34 Effect of the duration of water stress and fertility
variables on the diurnal stomatal resistance of corn during the first stress period of the 1975 dry season.




Table 2.21. Transpiration rates for maize during the veranico in relation to five fertility
treatments.
Sampling Days During Water Stress
Treatment 6/3 7/3 8/3 9/3 10/3 11/3 12/3 13/3 Avg.
----------------------- g H2/cm2/sec.
O-Lime 1/ 3.1 .93 .80 .42 .60 .38 .57 .76 .95
2/ 3.2 1.13 1.15 .63 .87 .38 .61 .71 1.09
Lime-Shallow 2.1 2.00 1.32 .60 1.44 .52 .55 .74 1.16
3.8 2.60 1.40 .81 1.42 .60 .68 .82 1.52
Lime-Deep 7.8 5.61 8.94 4.02 2.77 2.17 3.03 2.86 4.65
7.0 5.75 12.95 3.17 1.94 2.08 3.21 2.08 4.77
Broadcast-P 2.9 1.42 1.29 .71 .80 .39 .59 .42 1.07
2.4 1.64 .97 .97 1.67 .34 .53 .57 1.14
Banded-P 2.1 1.62 1.14 .49 .58 .55 .84 .52 .98
2.9 3.22 2.71 1.55 .77 .61 1.19 .52 1.68
1/Adaxial side of the leaf.
2/Abaxial side of the leaf.
00




84
Table 2.22 Effect of water stress and fertility treatments on corn
grain yields for the soil management experiment averaged
over three cropping seasons. Results are based on a 15.5%
moisture basis.
Treatment No stress Early stress Late stress
-----------------tons/ha------------------O-Lime 4.94 4.45 3.35
Lime Shallow 5.85 5.26 4.15
Lime Deep 6.14 5.12 4.83
Broadcast-P 5.91 5.54 4.78
Banded-P 3.69 3.70 3.30




85
the same period. In addition, plant water was used, the objective was to learn if the
stress resulted in approximately one gram corn roots were entering aluminum saturated
per day less of ear dry weight accumulation subsoil and still staying active. The second when compared to the no water stress treat- method was supposed to measure total root ment. About 50 kg/ha lost each day for 30 length per volume of soil. When using this
days which equals 1500 kg/ha or approxi- method, the main objective was to measure
mately the final yield difference between the total root distribution in relation to soil
stressed and non-stressed treatments. depth as influenced by the five fertility manA yield component analysis was con- agement treatments.
ducted to determine what effect the soil The percent root distribution as determanagement practices and what effect plant mined by the rubidium-86 method is shown
water stress had on the various yield compo- in Table 2.23. Both depth and lateral distrinents which influenced final grain yield. bution of roots are shown. Deep liming reDeep limed plants outyielded shallow limed suited in a fairly uniform rooting distribuplants because they had longer ears, more tion while 0-liming for example, showed a
kernels/row, more kernels/ear, more grains/ high concentration of roots in the 0-15 cm plant, and a better grain:cob ratio. Late soil layer. The general root pattern was as
water stress (Hanway, Stage 5) reduced grain expected. Many roots were shallow close to yield by producing fewer rows of kernels/ear the row and as lateral distance became and fewer kernels/ear. For early stress condi- greater, more of the roots were deep. The eftions, ear and kernel length/ear were highly fect of phosphorus application on root discorrelated to yield. This seems logical since tribution was not clearly shown. the plant stress occurred during the ear The second method, modified Newman
shoot formation stage (Hanway, Stage 2.5). technique, measures root length per 100
Root Distribution cm3 (Table 2.24). No effort was made to
Many of the findings shown so far in this analyze lateral root distribution per se, only report have been based on the corn plant's depth of rooting. The results show the beneroot distribution and ability to extract soil ficial effects of deep liming as well as liming water in relation to the low pH and high per- itself. The banded-P treatment shows more cent Al saturation of the Dark Red Latosol. roots and deeper root penetration than the To verify the previous results, root measure- broadcast-P treatment. The largest amount ments were taken when the corn plants had of roots in the 0-15 cm soil layer for the
just started to tassel (Hanway, Stage 4). Two banded-P treatment could be related to the methods were used. The rubidium-86 high concentration of roots in the band of
method is supposed to only detect the active phosphorus. portion of the root zone. When this method




86
Table 2.23. Percent root distribution for corn as determined by the
rubidium-86 method.
Soil Depth (cm)
Treatment Locationl 0-15 15-30 30-45
O-Lime 1 5.1 4.1 1.6
2 11.5 5.6 5.6
3 10.2 7.6 6.1
4 12.2 3.9 10.1
5 8.3 6.2 1.9
Mean 9.46 5.48 5.06
Lime-Shallow 1 7.7 1.0 10.6
2 9.1 5.7 8.6
3 2.8 10.4 4.6
4 7.6 2.4 11.4
5 6.6 5.5 6.0
Mean 6.76 5.0 8.24
Lime-Deep 1 6.2 6.2 2.6
2 7.4 5.8 5.7
3 8.5 5.2 3.5
4 8.8 7.6 9.6
5 5.2 7.4 10.4
Mean 5.72 6.44 6.36
Broadcast-P 1 15.7 2.8 0.6
2 8.3 7.7 2.2
3 14.2 10.1 5.1
4 4.4 7.5 7.0
5 6.2 4.1 4.0
Mean 9.76 6.44 3.78
Banded-P 1 5.7 11.9 2.5
2 6.0 1.6 7.4
3 9.3 6.6 4.7
4 2.8 13.5 7.2
5 4.3 11.9 4.6
Mean 5.62 9.1 5.28
-= 2.5 cm from plant within row. 5 45 cm from plant beside plant
2 = 17.5 cm from plant within row. between row.
3 = 15 cm from plant beside plant between row.
4 = 30 cm from plant beside plant between row.




87
Table 2.24 Root length (cm/100 cm3) for corn at the start of the
tasseling stage (Hanway, Stage 4) grown during the 1975
dry season.
Soil Depth (cm)
Treatment 0-15 15b-30 30-45
0-Lime 68.8 23.1 10.5
Lime-Shallow 99.4 58.4 24.7
Lime-Deep 96.5 76.2 40.4
Broadcast-P 103.0 26.1 4.4
Banded-P 133.6 52.9 10.0




88
Deep liming improves corn root proliferation. Left: shallow liming (0-15 cm depth).
Right: deep liming (0-30 cm depth). Both received 8 tons/ha of lime.




89
In conclusion, the rubidium technique is fully recover from the veranico, water stress probably a good method to use to determine measurements were taken for two days (Janif roots have reached a certain distance from uary 29 and 30, 1975) after 47.3 mm of rain a specific plant by a certain day. The New- had fallen in the ten-day interim. During the man technique is a good method to demon- stress period pan evapotranspiration, maxstrate the accumulated total root distribu- imum temperature, and solar radiation were tion of a crop from day of planting to day of quite high. sampling. The 1975 experiment is a continuation
Mulching Experiments of the mulching experiment that was iniAn additional experiment with corn was tiated in the 1974-1975 wet season. Some initiated to test both soil and crop manage- modifications were made to verify whether ment techniques for conserving soil mois- the grass mulch had a negative effect on corn ture. The treatments were: 1)Two depths of growth. A black plastic mulch was installed lime incorporation (shallow 0-15 cm, and along with a continuation of the grass mulch deep 0-30 cm), 2) dry molasses grass mulch treatment. The black plastic should increase 10 cm thick or no mulch, 3) two corn vari- soil temperature and at the same time coneties (Cargill-Ill and Agroceres-152), and serve soil moisture equal to the grass mulch. 4) two types of antitranspirants (Wilt Pruf Two lime depth incorporations and two antiand Phenyl Mercuric Acetate), with three transpirants were used again. To accommoreplications, date the plastic mulch treatment, the AgroThe principle objective is to determine ceres-152 comparison was not continued. to what extent the various management Six plots of Agroceres corn were planted on
techniques will reduce the negative effect of shallow limed plots only to allow for a gena "veranico" on crop growth and produc- eral comparison of the two varieties growing
tion. The experiment was conducted on a during the dry season.
previously cropped area which had received Methods and procedures for the mea400 kg P205/ha broadcast and 200 kg surement of plant growth and production
P205/ha applied in bands. An additional and for the measurements taken during the
134 kg P205/ha was band applied in this ex- plant water stress period were the same as periment. was explained in the companion experiA 15-day veranico occurred 66 days ments. To simulate a veranico, water stress
after planting which coincided with the tas- was imposed on the plants by withholding seling stage. Water stress measurements were irrigation water. The principle objective of taken for six days, January 14 through 19, this experiment was the same as in the 19741975). To learn if the plants were able to 1975 wet season crop management experi-




90
Overview of corn mulching experiment. Foreground: black plastic mulch.
Background: grass mulch.




91
ment: to study various soil and plant man- temperatures substantially. During the 1975 agement techniques which may reduce the dry season, the 0-45 cm soil layer under the
harmful effects of a veranico. The experi- black plastic was on the average 3 to 4 dement was planted on September 6, 1975 and grees Centigrade warmer than without harvested 141 days later. The plastic mulch mulching (Figure 2.37). Warmer soils were was installed eleven days after planting. responsible for increased plant growth in Plant Growth both seasons. For example, in August 1975
Mulching was shown to influence corn leaf area increased by 54 cm2 plant-i day-i
growth and development in both seasons. for the plastic mulched plants over the nonGrass mulch decreased plant growth and mulched plants. This is related to an average
development while black plastic mulch in- difference in soil temperature of 5.2 degrees creased plant growth and development in Centigrade.
relation to the non-mulched plots. Soil Water
During the natural veranico in 1974- Both mulches reduced surface evapora1975 rainy season, leaf area decreased in the tion of soil water by 4 to 7 mm in the top shallow limed plots for both Cargill and 20 cm of the soil during the stress periods. Agroceres. No decrease in leaf area was Table 2.25 shows that in the rainy season
noted for either variety in the deep limed crop stress period, deep limed plants used plots. In addition, deep limed plots showed 8.2 mm more water than the shallow limed a slightly superior leaf area index over plants. In the dry season crop, grass mulched
shallow liming during the growing season plants used less soil water during the simu(Figure 2.35). Cargill's leaf area was larger lated veranico than the other treatments bethan Agroceres but both varieties reacted cause of poorer growth. equally to mulching and depth of lime in- Plant Stress corporation in relation to water stress. No severe plant water stress was imposed
The effect of mulching on leaf area index on the 1975 dry season experiment, thus, and tasseling date is shown in Figure 2.36. the stress results were not too meaningful. The black plastic mulch produced corn tas- The natural occurring veranico in the seling from 10 to 15 days earlier than with 1975 rainy season, however,' was quite sethe grass mulch, vere. During that veranico, plant water stress
Soil Temperatures was greatly influenced by depth of liming,
The grass mulch reduced soil tempera- mulching, and their combinations. For extures by 2 to 3 degrees Centigrade in the top ample, the deep lime mulched treatment had 20 cm soil layer in both seasons. The black a six day leaf water potential average of plastic mulch, in contrast, increased soil -13.5 bars. Shallow liming without mulch




* Agroceres-Shallow Lime
E o Agroceres-Deep Lime Veranico
S4 -0 Cargill-ShallowLime
E
A a Cargill- Deep Lime o
4)
3
50% Tassel
Lo
4
0
_ f r I I I I I I I
0 20 30 40 50 60 70 80 90
Days After Planting
Figure 2.35 Effects of varieties, mulching and depth of liming on leaf area
index of corn plants grown during the 1975 rainy season.