Title: Cornell TropSoils program review triennial review
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00080650/00001
 Material Information
Title: Cornell TropSoils program review triennial review
Series Title: Cornell TropSoils program review triennial review
Physical Description: 28 leaves : ; 28 cm.
Language: English
Creator: Soil Management Collaborative Research Support Program -- External Evaluation Panel
Publisher: Cornell University
Place of Publication: Ithaca N.Y
Publication Date: 1987
Subject: Agricultural extension work -- Evaluation   ( lcsh )
Agricultural extension work -- Brazil   ( lcsh )
Agricultural development projects -- Brazil   ( lcsh )
Genre: non-fiction   ( marcgt )
Spatial Coverage: Brazil
Statement of Responsibility: report of External Evaluation Panel.
General Note: Caption title.
 Record Information
Bibliographic ID: UF00080650
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 162176249

Full Text


Report of External Evaluation Panel

Section 1. The Nature of the Program


The Panel visited Cornell September 16-18 and CPAC, Brazil

September 19-25. At Cornell, presentations were made by staff and graduate

students involved in the program. At CPAC the panel had the opportunity to

discuss the field and laboratory programs in detail, to visit some of the

farms engaged in intensive production on acid savanna soils and to discuss

the program with CPAC staff. The Panel wishes to thank the Cornell

faculty, the EMBRAPA and CPAC staff and the students for the excellent

interaction which took place during the visits. This contributed greatly

to the work of the Panel.

Several important aspects of the program, including comments and

suggestions on future programs are discussed in Section 2 and Section 3.


The Cerrado of Brazil has about 200 million ha lying south of the

Amazon Basin at a latitude of 6 degrees to 20 degrees south at elevations

ranging between 1100 and 1300 meters. Rainfall during the wet season,

October to April, varies between 1000 mm in the south to 2000 mm in the

the north, with the CPAC station averaging about 1600 mm. Rainfall is more

than adequate for good production during the rainy season, though there are

relatively short dry spells which can have a severe impact on crop growth.


The soils of the Cerrado are dominated by the soil orders Ultisols,

and oxisols and in the Cerrado these soils are extremely low in plant

nutrients, particularly calcium and phosphorus, and are highly acidic.

However they have excellent physical characteristics and when nutrients are

supplied are capable of giving good yields. The development of the Cerrado

soils using modern technology of fertilizers and lime, mechanisation,

improved varieties and capital have demonstrated that large areas of some

of the world's poorest soils can be reclaimed for a highly productive


Development Relevance of the Program

The Ultisols and Oxisols of the Cerrado represent a substantial

part of the global area of these soils, but there are very large areas of

similar soils in Africa and South East Asia. Outside Brazil, these are

almost entirely farmed by small farmers except in the plantation areas of

South East Asia. Mostly such farmers use low or nil inputs of plant

nutrients and depend on long term fallows to sustain the low yield levels

usually obtained. The relevance of the CRSP work in Brazil to improving

the productivity of small farmers in Africa and Asia lies in the importance

of the Cerrado research in providing an understanding of the physical and

biological principles involved in reclaiming these soils from poor scrub

and grassland into highly productive agricultural land. The development

that has already taken place on Cerrado soils also provides a unique

opportunity to define the second generation problems of maintaining soil

fertility and increasing productivity, both from the chemical and physical


points of view. It also provides an opportunity to study techniques for

reducing the investments in fertilizers, especially nitrogen, which wouldbe

of specific interest to small farmers.

As knowledge and understanding of the physical and biological

problems of farming these soils are improved, the ideas and techniques

generated by the research will be tried in the very different economic and

social setting of small farmers in Brazil and elsewhere. (Section 3).

Problems being addressed

An essential part of the work of the TropSoils program is a clear

definition of the problems that are being addressed and the relevance of

the solution of those problems to agriculture development in the various

agro-ecological zones. The problem orientation is implicit in the

statements in the Cornell document and the on-site briefing report but not

always explicit. Furthermore descriptions of research topics are sometimes

intermingled with problem description. For example leaching of nitrates is

a research topic; the problem is that a substantial portion of the

nitrogen from fertilisers or organic matter is not utilised by crops. It

is inevitable of course that a research program will consist of a number of

time bound researchable topics, especially where graduate students are part

of the program. All of these will have some relevance to the problem in

the broadest sense, but some will be of much greater importance in

addressing the problem in hand and hence the need to select priority topics

within the overall problem area.


The Panel also considers that improved presentation would make it

easier to understand the priority being given to the solution of some

specific problems. For example the program on deterioration of soil

structure after several years of continuous cultivation, is based on a

rather vague problem description the importance of which is somewhat

speculative so the priority of this program in relation to the others is

not readily ap4rent.

The usefulness of clear problem definition is however well

illustrated by the program in Brazil. As indicated earlier several million

ha of Cerrado soils have been reclaimed from stunted bush and poor

grassland into productive agriculture. This reclamation was done under an

economic climate where fertilizers and lime were supplied below cost and

where an easily saleable crop, soybean, could be grown for a rapidly

expanding market. In such a climate the real costs of reclamation were not

a problem.

Thus the TropSoils program is not involved in problems of

reclamation (though its predecessor program was), the technical aspects of

which are now reasonably well understood, but in the problems of more

efficient management of reclaimed Cerrado soils. In the Panels' view the

more specific problems being addressed include those dealing with the

production and decay of organic matter and the quantitative assessment of

anion and cation movement in relation to water movement in the soils.

Improved knowledge of these processes would lead to more efficient

fertilizer, green manure and crop residue management and would provide the


technical know-how for developing new cropping or crop-animal systems that

could better use limited amounts of plant nutrients from fertilizers and

organic matter, including that supplied by green manure.

A second thrust of the program addresses the potential problems

which could arise through continuous intensive cultivation of the Cerrado

soils. While such soils appear to have an extremely stable and favorable

structure in spite of their high clay content there is some evidence that

continued arable farming does lead to some form of structural deterioration

in the subsoil.

Human Resources For the Program


The human resources for the program are a combination of Cornell

faculty, graduate students and staff of CPAC. The management of the

program is to be congratulated on an outstanding job of mobilizing the

skill and interests of the university faculty. This has been a major

factor in reaching the high scientific quality that the program has

achieved. The program has also captured the interest of CPAC, resulting in

strong support for the program from the Brazilian authorities. The

presence of graduate students and Cornell faculty in Brazil and the visits

by experienced staff from Cornell has provided an intellectual stimulus

which is much appreciated by the Brazilian scientists at the station.



The CRSP enjoys good relationships with CPAC based on many years of

productive interaction predeeeeeing the CRSP. CPAC welcomes the depth with

which the CRSP studies are carried out and feels they are well defined and

well focused. CPAC is not able to conduct the more fundamental research

work being done by the CRSP because of its broad mandate and limited

resources. CPAC would like to be able to provide more support to the CRSP,

but as their resources have been cut back over time, they have had to

reduce support to the CRSP in order to continue with their own priority

projects. A closer agreement on priorities might alleviate this.

CPAC scientists have expressed an interest in being more involved

in planning CRSP research. Some characteristics of the type of research

being conducted under the CRSP, however, have held this interaction to a

lower than desired level. When the graduate students arrive in Brazil,

their individual projects have already been approved by CPAC and they

normally have a limited amount of time in which to conduct the research

due to graduation pressures. Because of this they tend to become involved

immediately in the implementation of their projects before strong personal

contacts with CPAC staff have been developed. This problem may be lessened

as CPAC scientists return from studies at Cornell. /the short run these

scientists will be acquainted with the students, and in the longer run,

they will have the language capability and knowledge of the Cornell and

CRSP systems to facilitate interaction. Also, assuring that the students

work only on projects of high priority to CPAC will facilitate the

provision of CPAC -taff time and other resources for collaboration on CRSP



Section 2. The Research Program and its achievements

The achievements of the program have been described in detail in

the documentation from Cornell and the research site and the results are

summarised in Annex I. (documentation provided by the research group).

The comments in this section are confined to the two general areas of

quantitative description of water and chemical budgets and soil tillage and

root restriction.

Quantitative Description of Water and Chemical Budgets in Acid savannah

The Cornell TropSoils Program Review Document dated September,

1987, page 9, identified three research topics to be pursued by the future

CPAC Collaborative Research Program. These are:

1. Nitrogen management of acid savanna soils,

2. Quantitative description of water and chemical budgets in acid

savanna soils, and

3. Soil constraints to management of acid savanna soils.


Specific research projects proposed to implement Research Topic

No. 2 are Project No. 104, Nitrogen Transformation and Movement in Acid

Soils of the Tropics, and Project No. 107, Crop WAter Requirements in Acid

Savanna Soils.

The objectives of Project No. 104 are:

a. Develop a comprehensive description in simulation model form of

nitrogen movement and transformation in cropped soils of the acid

soil regions of the tropics.

b. Use the model as a guide in interpreting previous studies and in

designing further field experiments to increase understanding of

nitrogen fate in these soils/crop systems.

c. Develop a simplified model of nitrogen fate in these soil crop

systems that will be useful in guiding nitrogen management


The objectives of Project No. 107 are:

a. Determine the components of the water budget in the cropped Cerrado



b. Quantify the effects of soil tillage practices upon water

availability and soil-water movement and their impact upon crop

yield, evapotranspiration, and transient soil-water regimes in a

manner useful to irrigation and crop production programs.

c. Develop and test a simplified model relating water use to crop

yield, constructed to be useful in extending experimental results

to other locations.

Clearly, because of the close linkage between water and nitrogen

transport, the objectives of Project 104 cannot be attained without first

accomplishing the objectives of Project 107. Likewise, to predict crop

yield as a function of water use as called for in objective c. of Project

107, a quantitative knowledge of the nitrogen budget is essential.

Not only is it impossible to pursue the objectives of the two

projects within Topic 2 independently, but there is close linkage between

these objectives and the research within Topics 1 and Topics 3. The

quantitative description of nitrogen transformation and movement in soil

called for in Project 104 cannot be made without the information to be

developed on nitrogen management in Topic 1. Objective b. of Project 107

calling for quantification of the effects of soil tillage on water movement

and crop yield clearly cannot be fully attained without the results of

Topic 3 on soil constraints to management of acid savanna soils.

- 10 -

The point is that all of the projects proposed in the Cornell/CPAC

collaborative research program are closely interrelated. The objectives of

some individual projects cannot be attained without first having the

results of other projects. Rather than standing as a set of parallel

projects that can be pursued independently it would appear that a

heirarchial arrangement of research projects would be more productive.

It seems to the Panel that rather than standing as one of three

parallel topics, Topic 2, obtaining a quantitative description of water and

chemical budgets in acid savanna soils, is really the overall objective of

the Cornell/CPAC program. All of the other projects produce information to

help fill knowledge gaps required to accomplish this.

Accomplishing this overall objective will require an integrated

approach involving overall program management from the top. The systems

approach outlined in the projects of Topic 2 provides an excellent

mechanism to accomplish this management. First, all existing information

from past experiments and from literature references needs to be

incorporated into the quantitative predictive models. Where gaps occur,

new research needs to be outlined to fill them. Such overall management

will require the long turn involvement of a scientist with a holistic view

of the entire program. The pieces can be filled in by graduate student

programs, but without the overall management these pieces will not add up

to a whole that is g-eater than their sum.

- 11 -

Soil Tillage and Root Restriction

This project, Project 108 is designed to characterise the root

restricting zones in Cerrado soils.

There is circumstantial evidence that the Cerrado Oxisols which

have a very stable structure deteriorate after a period of continuous

cultivation. This deterioration takes the form of a hard and compact

layer below disk plow depth resulting in poor root development and

consequently lower yields. The evidence for this is based on the

performance of soybeans at the National Soya Bean Center, over a period of

10 years of mono cropping.on farmer observations that shallow rooting

occurs even in adequately fertilized soils and on the fact that erosion of

surface soil down to the compacted layer takes place.

Experimental evidence supporting this hypothesis has been obtained

from pot experiments whereby clay soils compacted to differing bulk

densities displayed barriers to root penetration. Chisel tillage

experiments have shown enhanced yields from this experiment.

The Panel recognizes the potential importance of structural

deterioration of the soils which do not appear to have any of the

recognized mechanisms (freezing, shrinking-swelling) for improving

structure. The apparent absence of soil fauna e.g. earth worms at depth

would also contribute to poor recovery of structure. Accomplishment of the

objectives of this research will therefore require attention to soil

properties other than mechanical compaction.

- 12 -

Section 3. Future Work


Since the original proposals for the acid savanna soils were

developed in October of 1980, major changes in the thrusts and shape of the

program have taken place. Financial cuts led to a revised program being

presented in April of 1982. This program had thee major thrusts: To

increase the efficiency of fertilizer use in acid savanna soils; to

develop improved methods of soil acidity management; and to develop

methods of characterizing soils so that results may be applied to other

acid infertile soils of the tropics.

The actual projects undertaken following this program formulation

have included only a part of it; as indicated in section 1 work on

nutrient efficiency has concentrated on nitrogen efficiency, particularly

that from leguminous crops. The work on soil acidity management has been

concentrated on movement of calcium ions. There is not an active program

by the TropSoils group on characterising soils through the project on

linking soil color to minerology and water table measurements could be

regarded as part of this.

The proposals for the 1987-1992 program follow closely on the same

lines. At this stage the Panel would not comment on the details of these

proposals which in any case will be the role of the peer review panel.

Rather our comments are focused on the general direction or strategy of

the program.

- 13 -

Future Strategy

As indicated above the original and modified proposals were set out

as a series of thrusts each of which contained several research projects,

each project having a research objective or objectives. The letter of July

21, 1987 from the Management Entity to program coordinators sets out

specific requirements for the format for the research proposals. The Panel

strongly endorses these requests and stresses the need for the projects to

be set in the context of development relevance of the subject. It also

stresses the need for a well defined problem statement that differentiates

between the problem and the research objectives that would lead to the

solution of that problem.

The Panel also considers that more attention should be given to

formulating a specific strategy with a multi-year time horizon. It

recognizes that factors beyond the University control can have a drastic

impact on such a plan. Nevertheless the development of this would provide

an excellent opportunity for CPAC and Cornell to look at their congruent

long term needs as related to the development of Cerrado agriculture. It

would provide the umbrella strategy under which the work of graduate

students, Brazilian scientists and Cornell faculty could operate and it

could lead to stronger synergistic effects from the combination of the

participants. To make such a plan worthwhile thee would have to be

obligation on the part of both the TropSoils and CPAC management to give

priority support to the agreed program. Clearly the on-site coordinator

should play a major role in developing this plan.

- 14 -

The Appropriate Role of Models in TropSoils Research

.The Panel has expressed concern in the past that simulation

modeling in some TropSoils programs has not been effectively integrated

into the theoretical and experimental research programs being conducted.

Too frequently simulation models are treated as ends in themselves and

developed as separated projects that treat one component of the overall

system and end with publication in a scientific paper. The Panel is

considerably encouraged by the presentations made by members of the Cornell

team and by the publications made available to them in the briefing

packet. The capability and desire now appears to exist within this team to

do much more. The modular concept for simulation models developed in the

publication by Buttler and Riha to allow users to incorporate additional

procedures and to link existing models into base models establishes the

necessary framework. The comprehension of the specific biological,

chemical and physical processes involved in the soil-plant-atmosphere

continuum demonstrated by the publications of Lathwell and Grove, Lathwell

and Bouldin, Wolf, de Wit, Janssen and Lathwell provide what's needed to

put the meat on this framework. The scientific talent is in place, much of

the needed basic scientific information has been developed, the time is

ripe to begin the process of developing an integrated model for acid

savanna soils.

This model must include transformation and transport processes that

involve water, nitrc en, phosphorus, calcium and aluminum that impact crop

performance. Such a model would provide the predictive capability needed

- 15 -

by managers of crop systems on these soils to assess the potential impact

of alternative management choices on crop production under specific

environmental conditions. This would permit a manager to take into account

the cost for each management alternative and choose that with most


The failure of scientists to use models to help solve management

problems stems to a large extent from the fact that they do not perceive

this to be the job of the scientists. Scientists often have the concept

that their job is to discover basic principles and publish them in the

scientific literature. The assumption is that someone else will integrate

this information into management procedures that will solve problems; that

integration of scientific information into packages to solve management

problems is not science. This orientation fails to recognize the value of

one of the most rapidly emerging and productive scientific

disciplines-systems science.

Systems science is that branch of science concerned with the

solution of management problems by use of the tools of science. it

recognizes the fact that real world problems are not water problems, or

pest problems, or plant nutrition problems, or erosion problems; they are

just problems -- with water constraints, pest constraints, nutrition

constraints and erosion constraints. Furthermore, solutions to real

problems do not come in packages labeled physics or chemistry, plant

physiology or weed science, micrometeorology or hydrology, soil science or

agronomy, economic. or marketing. They have interdisciplinary labels with

noas many disciplie name s a re needed to solve the problem.-

- 16 -

The scientific method requires the formulation of hypotheses and

experimentation to test them,. Yet the systems within which real problems

are embedded are frequently not amenable to direct experimentation. Direct

experimentation on complex systems is often too costly, too risky or it

takes too much time to get the needed result. When it is not practical to

perform direct experimentation, systems scientists construct a model of the

system. The model stands as surrogate for the real system. A model is a

description of the essential components of a real system and how they

interact. In the field of engineering, models often consist of miniature

physical representations, such as for a dam. More frequently, with the

advent of powerful and affordable computers, models are now constructed in

numerical or symbolic form to run in a computer to take advantage of

reduced cost.

The model allows the scientist to perform experiments by changing

either components or the environment of the system and determine the effect

on system response. For a model to be useful it must accurately represent

the most important attributes of the real system,. The first step in

establishing this is to verify that the output of the model is consistent

with existing observations about the real system in as many conditions as

data are available. Once verified, new conditions can be imposed on the

model, or components of the model can be altered to predict the system

response within a new environment or with an altered management scheme.

Before such predictions can be relied upon, validation experiments need to

be conducted on the real system under controlled conditions where some

components of the environment or management are changed and direct system

LrbPOLLZe IS aQsC1----------- s L maud--.-

- 17

Ultimately the goal is to construct models of real systems that can

be used by managers to achieve a specific goal. Clearly with a system as

complex and difficult to work with as the soil-plant-atmosphere system for

acid savanna soils immediate products that can be placed in the hands of

users cannot be expected. But if such a goal is ever to be achieved we

must begin somewhere. And the process of creating such a model is an

effective means of integrating existing scientific knowledge into a form

that can identify gaps. It also can serve as an effective communication

tool to link network members into an effective interdisciplinary team.

Effective inter team communication should be particularly effective if the

modular approach proposed by Buttler and Riha is used. This could permit

the fundamental physical, chemical and biological processes understood best

by scientists at the cutting edge of their discipline to be directly

incorporated into the model. Competing modules developed by other

scientists in the same field could then be substituted directly into the

model and evaluated on the basis of improvement in the predictive

capability of the overall model.

To capitalize on this systems approach, organization of the

Cornell/CPAC team would require a heirarchial structure. The primary

objective of the program would have to be directed toward the development

of a comprehensive systems model of the soil-plant-atmosphere system for

acid savanna soils. Some person would have to accept responsibility for

overall system design and coordination. Responsibility for design and

implementation or specific system modules would also need to be assigned.

- 18 -

Module teams would initially have a monumental task of incorporating

existing.scientific knowledge into their sub-model and developing the

accompanying database. An immediate return on this investment would be a

clear identification of knowledge gaps that could be filled by new

research. This could significantly impact the direction of student

research programs and provide an immediate use of student research results

beyond that of publication in a scientific journal.

It would seem most practical to place primary responsibility for

overall systems design and system module development with the Cornell

faculty. Equally as important as model development will be the job of

model validation. Since this can only be done on the real system, primary

responsibility for this phase should probably rest with CPAC and the

Cornell permanent staff in Brazilia. Graduate students could effectively

work and be supervised by staff at both locations. Close working

relationships among team members working on any specific module at both

locations is essential. Frequent visits by staff members at each other's

institutions would almost be essential to provide the real time feedback to

keep such a dynamically evolving project on course.

The opportunity to implement a systems approach to solving

management problems for which TropSoils was established appears to be great

within the Cornell/CPAC team. The Panel strongly recommends that the team

consider this as an alternative approach for team structure and research

management and present an outline in this format at the December Tropsoils


- 19 -

Deterioration of Soil Physical Conditions Under Long Term Continous

There is considerable speculation but not much hard information

about the magnitude and nature of this problem. Indeed it is possibly of

such a nature that a multidisciplinary team would be needed to tackle it

effectively. The problem, as seen by the Panel, is the need for a better

definition of what actually takes place in such soils over time. For

example, the relatively large amounts of lime may alter the charge

characteristics of these poorly buffered soils, leading to increased

dispersion of the clay. This is supported by the observation that water

dispersible clay in some Oxisols increases with cultivation. Also

changing the pH from that of the natural environment may kill organisms

such as earth worms that could help reverse this effect.

The panel recognizes that the very limited resources of TropSoils

make it possible to carry on only the limited range of research already

under way. gut the development of a multi-year program would provide the

opportunity to involve more support from EMBRAPA. The Panel would endorse

work that would lead to better characterisation of the extent and causes of

the problem.

The Panel would therefore recommend that work continue on assessing

the magnitude of the problem, on attempting to quantify the impact on

yields on well documented sites and the soil characteristics that appear to

- 20 -

encourage structural deterioration. The panel suggests that the research

should not focus solely on the mechanical aspects of long term cultivation

but should also look at the physico-chemical and'biological aspects of

structural degradation.

Diffusion of Research Products

The Output of the CRSP/CPAC Program

CRSP projects develop three different kinds of research products.

One is the development of new biophysical knowledge which has global

applicability. This product is diffused through theses, journal articles,

bulletins, state-of-the-art papers, presentations at professional meetings

and in general interaction with other scientists. Each individual paper or

presentation has value in and of itself and need not be reported in any

particular sequence nor necessarily be based on any single orientation.

The Cornell/CPAC TropSoils program reports an impressive array of products

of this nature.

A second kind of research product is created when a new research

method or technique evolves during the research process. CRSP scientists

have proved that a short-cut procedure can be used for evaluating nitrogen

mineralized after incorporation of plant material in small bare fallow

plots as a technique for screening large numbers of potential legumes as

green manures. They were also successful in developing a technique, using

polyethylene bags, to bury soil/green manure samples in the field allowing

mineralization to proceed normally while preventing nitrate escape to the

surrounding soil. This is a labor-saving technique to screen large numbers

-of legumeo ao &ourczc of nitrogen.

- 21 -

CPAC sees these products, emanating from the mission oriented

research, as the necessary basis on which further advances in yields on the

developed Cerrado soils can be made.

However, the collaborative nature of the CRSP demands a third

product for the collaborating (and other) countries. This is the'

development of new technology that helps farmers to solve their most

pressing production problems. This requires the integration of biophysical

knowledge into a practice, or set of practices (the new technology) that

farmers in the area are able to use and are willing to adopt.

Extrapolation and validation

Extrapolation and validation can take two forms. One is to

quantify soil-water-plant-nutrient relationships as is being done in the

modeling efforts, then extrapolate results to other locations and validate

the models through tests in the extrapolation locations. The Pnel

encourages this process as discussed elsewhere, even though it is seen as a

fairly long range process. It would require a faculty person from Cornell

to serve as an integrator who would work with other Cornell faculty and

with CPAC scientists as models are devised and tested. CPAC staff who are

returning with degrees from Cornell and who are familiar with the modeling

procedure would be the logical choices for collaboration.

- 22 -

The second form of validation is one with a socio-economic

component. Essentially this is directed at assuring that a technology

which is physically and biologically promising, will also operate
successfully under real farm condition. The first stage in this is a

preliminary economic evaluation. This does not have to be a sophisticated

procedure but should be sufficient to eliminate those technologies which

have no prospect of succeeding under farm conditions. An important aspect

of this is the labour component. For example the use of legumes and green

manures has a significant cost in terms of farmers' time, both for growing

the crop and incorporating it into the soil. Some of this requirement may

come at a critical time in the farm schedule; for example incorporation

into the soil gives more efficient use of the N, but mulching the surface

needs less labour and hence may be the farmers preferences.

Clearly this initial screening can be used only to eliminate

unsuitable technologies but the others must be validated under the array of

real farm conditions in which they are expected to be used; farmers must

be incorporated in the evaluation process. Though no validation has been

done to date, the Panel feels there is some technology which has been

developed suficiently on the CPAC station that it is ready to be validated

in farmer s fields.

One example is that from the research currently being conducted
under Project 103 Six legumes will be selected for further screening for

dry season survival, these six could be tested against farmers' usual

- 23 -

practices on at least 10 farms in addition to the CPAC station. The soils

and previous practices would have to be characterized at each location, but

no attempt should be made to standardize or make'corrections other than

assure that the same fallow or non-legume crop is used. By selecting a

wide range of soil environments, the selected legumes would be evaluated

and/or validated for a number of biophysical and socio-economic conditions

encountered in the Cerrado soils. Small and large farms, for example,

could both be used for the on-farm research.

On-farm research on the Cerrado and related research at CPAC would

require an integrator of CPAC to carry out the same kind of function as the

integration of modelling on the Cornell campus. The CRSP team leader would

be the logical choice for this assignment, provided he could be relieved of

some of his other duties.

In conclusion the Panel is aware that the task of on farm testing

would add a new dimension to the work of the CRSP, a dimension that can

make heavy demands on manpower and transport and is difficult to fit into

the research program of a graduate student. CPAC is, however,

strengthening its farming systems unit with a view to doing more work on

on-farm testing and it, in co-operation with EMBRATER should provide the

logistical support for the work. Involvement of graduate students at the

farm level has an important training and orientation aspect which would be

of substantial value in training such students in problem definition.

- 24 -

On Site Management

The duties of the on-site co-ordinator are many and diverse. And

the progress reports indicate that he has to spend a large amount of time

on the logistical aspects of the project. Graduate students need a lot of

support in order to get on with their thesis work and there are many other

aspects of the program where a facilitator is essential. Nevertheless it

is not very productive of a professional's time to do these essential but

non-scientific tasks. The panel therefore urges the management to explore

other means by which these logistical support tasks could be done, giving

the on-site coordinator more time for the research program.

Summary ogRecommendations

The Panel strongly supports the Management Entity in its requests

to the Program Co-ordinators for a clear statement of the problems being

addressed and their relevance to development.

The Panel recommends that attempts to improve the interaction of

CPAC staff and graduate students from Cornell be continued.

The Panel recommends that Topic 2 obtaining a quantitative

description of water and chemical budgets in acid savanna soils be used as

the definition of the overall objective of the Cornell/CPAC Program. The

development of a holistic approach will require the involvement of a

scientist with this attribute.

- 25 -

The Panel suggests the formulation of a longer range strategy for

the joint program. The development of a multi year program will provide an

opportunity for Cornell and CPAC to examine their congruent long term

needs. The on-site co-ordinator should have a major role in formulating

this strategy.

The Panel believes that there is a major role for modelling in the

program especially in the soil-plant atmosphere continuum and recommends

that this work continue to receive major emphasis; the primary

responsibility for overall systems design and system module development

should be with the Cornell faculty.

The Panel endorses work that would lead to better characterisation

of the extent and causes of the problem of deterioration of soil physical

conditions. Work should focus on both physical and chemical aspects of

structural degradation.

The Panel recommends that the work at CPAC move to on-farm

validation in some of the projects. This should follow an initial

screening of potential technologies with regard to their likely economic

benefits. On-farm validation has an important training and orientation

dimension for graduate students.

The Panel recommends that the on-site co-ordinator be relieved of

some of the non-scientific tasks which, while very important, could be done

equally well be'sjmeone else.

- 26 -


Significant research results to date from the TropSoils Program and

some possible management implications include the following items:

1) A green manure, macuna preta (Macuna aterrima (Piper & Tracy)), was

found to provide 260 kg/ha as a sole source of nitrogen for

production of 6.8 t/ha of maize grain.

2) Incorporated macuna preta showed a marked residual effect,

supplying a limited amount of nitrogen to a second maize crop while

serving to increase the indigenous population of mycorrhiza in the

soil, thus improving phosphorous uptake.

3) The quantity of inorganic nitrogen accumulated in fallow soil was

significantly proportional to nitrogen uptake by maize, proving

that a short-cut procedure can be used for evaluating nitrogen

mineralized after incorporation of plant material in small bare

fallow plots as a technique for screening large numbers of

potential legumes as green manures.

4) Burial of soil/green manure samples in the field enclosed in

polyethylene bags allowed mineralization to proceed normally,

preventing nitrate escape to the surrounding soil, thus serving as

a labor-saving technique to screen large numbers of candidate

legumes as-sources of nitrogen.

- 27 -

5) Incorporation of a green manure to Acrustox and Haplustox soil

samples reduced sulfate adsorption, increased pH levels, and

resulted in manure incorporation other than nitrogen supply.

6) Soil genesis studies verifying the presence of a water table within

2m of the surface of a red-yellow Acrustox during a "veranico" dry

spell emphasized the importance of developing management strategies

to take advantage of soil water made available by deep rooting of

annual crops grown on these soils.

7) High mechanical impedance in a Haplustox under cultivation for 11

years from the Sao Gotardo region of Minas Gerais State, was

partially alleviated by chisel plowing, permitting deeper root

proliferation, leading to a significant yield increase in rainfed


8) Addition of calcium to acid subsoils was unable to overcome the

detrimental effects of even slight soil compaction on wheat root

penetration; this serves as an alert for Cerrado region farmers

that physical barriers to root penetration, aggravated by

continuous disc tillage practices, may deter root growth in

improved profiles just as severely as chemical barriers constrain

root growth in unamended soils.

- 28 -

9) Compaction of a high clay content (70%) Haplustox in a greenhouse

experiment restricted root penetration much more severely than the

same soil with lower clay content. One df the causes of concern

with this finding is that even those soil maps that do exist for

the Cerrado region do not specify soil texture classes at a level

of detail useful for delineating these problematic soils.

10) On-farm soil sampling in fields subjected to 9 years of heavy disc

primary tillage confirmed the development of root-restricting high

mechanical impedance on high clay content (80%) Acrustox sites in

the Southeast Federal District. Nearby fields with 10 cropping

cycles under disc or moldboard plow primary tillage retained

desirable physical characteristics in spite of normal field traffic

and secondary tillage by disc harrowing.

University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs