IAEA-311-D1-RC-810.3 LIMITED DISTRIBUTION

Working Material The Development of management Practices

for Sustainable Crop Production Systems on Tropical Acid Soils through the Use of

Nuclear and Related Techniques

Report of the Third Research Co-ordination Meeting of the Co-ordinated Research Project,

Ouagadougou-Burkina Faso, 18-22 August 2003

Reproduced by the IAEA Vienna, Austria, 2003

NOTE

The material in this document has been agreed by the participants and has not been edited by the IAEA. The views expressed remain the responsibility of the participants and do not necessarily reflect those of the government(s) of the designating Member State(s). In particular, neither the IAEA nor any other organization or body sponsoring this meeting can be held responsible for any material reproduced in the document.

JOINT FAO/IAEA DIVISION OF NUCLEAR TECHNIQUES IN FOOD AND AGRICULTURE

INTERNATIONAL ATOMIC ENERGY AGENCY FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS

Report of the Third Research Co-ordination Meeting of the Co-ordinated Research Project,

Ouagadougou-Burkina Faso, 18-22 August 2003

FELIPE ZAPATA (Scientific Secretary)

IAEA-311-D1-RC.810.3

Working Material Produced by the IAEA

Vienna, Austria 2003

EDITORIAL NOTE

In preparing this publication for press, staff of the IAEA have made up the pages from the original manuscripts as submitted by the authors. The views expressed do not necessarily reflect those of the governments of the nominating Members States or of the nominating organizations. Throughout the text names of Member States are retained as they were when the text was compiled. The use of particular designations of countries or territories does not imply any judgment by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA. The authors are responsible for having obtained the necessary permission for the IAEA to reproduce, translate or use materials from sources already protected by copyrights.

CONTENTS

REPORT..................................................................................................................................... 1

1. INTRODUCTION ............................................................................................................ 1

2. THE THIRD RESEARCH CO-ORDINATION MEETING (RCM)............................... 2

2.1. Objectives ........................................................................................................... 2 2.2. The Meeting........................................................................................................ 2

3. CONCLUSIONS AND RECOMMENDATIONS ........................................................... 4

ACKNOWLEDGEMENT ......................................................................................................... 4

4. REFERENCES ................................................................................................................. 8

ANNEX I. LIST OF PARTICIPANTS .............................................................................. 19

ANNEX II. AGENDA ......................................................................................................... 23

ANNEX III. ABSTRACTS ................................................................................................... 27

ANNEX IV. SUMMARY OF THE EXPERIMENTAL ACTIVITIES TO BE COMPLETED BY 2004................................................................................... 41

REPORT

1. INTRODUCTION

Against the background of the projected increases in world population there is a need to increase food production through intensification of agricultural production in the already cultivated land or expansion of the land into cultivation. Land for potential expansion of the agricultural frontier lies in the tropical rainforest and savannas regions dominated by acid infertile soils. The tropical rainforest ecosystem should be preserved to conserve biodiversity and protection against climate change. Thus, the most favoured lands are concentrated in the savanna agro-ecosystems, which are located in the sub-humid tropical region, and comprise a sizeable amount of the agricultural land in many countries of Africa and Latin America. In terms of agro-climatic conditions, the savannas present suitable conditions for rainfed agriculture. The soils, predominantly Ultisols and Oxisols, are typically acidic and infertile. In other soils, the problems of acidity are likely to increase due to increasing CO2 levels in the atmosphere, depletion of soil organic carbon, the use of ammonium-based N fertilisers and other processes.

Several international programmes of CGIAR institutes (CIAT, IITA, IFDC, CYMMIT, ICRISAT, WARDA and others) have concentrated their activities on developing technologies suitable for sustainable increases of agricultural production in the savannas. Currently there is a fast intensification through the development of intensive cropping and cultivation systems dictated by the regional and world markets. This intensification, however, must be achieved without degrading the natural resource base. There are several examples of accelerated rate of resource base degradation due to cultivation of marginal lands, and use of inappropriate soil management and conservation practices. Therefore, the overall goal of this project is to develop integrated soil, water and nutrient management practices to increase and sustain productivity of tropical acid soils. This can result in a major contribution to food security in the Sub-Saharan Africa and Latin America. Nuclear techniques will be employed to gather precise and quantitative information on the dynamics of water and nutrients in cropping systems and to monitor the value of the interventions designed to alleviate soil constraints to agricultural production and to conserve the natural resource base.

Recognizing the strategic importance of the tropical acid soils of the savannas as a new agricultural frontier, the Joint FAO/IAEA Division convened a Consultants Meeting in Vienna (March 1-3, 1999) to review advances in the approaches for sustainable intensification of agricultural productivity of the savannas and to elaborate a detailed work plan of a new Co-ordinated Research Project (CRP). Based on the recommendations of the Consultants Meeting, the Joint FAO/IAEA Division through the Soil and Water Management & Crop Nutrition Section started implementation of a research network comprising 7 research contract holders from developing countries (Africa and Latin America) and 5 agreement holders from advanced research institutes with the following specific objective: “Improve agricultural production of tropical acid soils through the use of adapted plants, the amelioration of soil acidity and infertility, and better soil, water, nutrient and crop management”.

The First Research Co-ordination Meeting (RCM) was held in the IAEA Headquarters, Vienna, Austria, from 5-9 June 2000. The Second RCM was organized in collaboration with EMBRAPA (Brazilian Agricultural Research Corporation) in Brasilia, Brazil, from 11 to 15 March 2002. This report describes the activities developed during the Third RCM convened in Ouagadougou, Burkina Faso, from 18 to 22 August 2003.

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2. THE THIRD RESEARCH CO-ORDINATION MEETING (RCM)

This meeting was organized 17 months after the second RCM in collaboration with the “Institut de l’ Environnement et de Recherche Agricole” (INERA) of Burkina Faso. Six of the eight Research Contract (RC) holders, two Research Agreement (RA) holders, two representatives of the other two RA holders and the Technical Contract (TC) holder attended the meeting. The venue was the conference room of the Hotel Splendide, Ouagadougou, Burkina Faso. The local organizer was Dr. Vincent Bado, the research contract holder from Burkina Faso. The full list of participants is shown in Annex A.

2.1. Objectives

The objectives of the Third RCM were the following:

a) To review research results obtained during the reporting period in accordance with work plan of the project, and

b) To assess overall progress in the implementation of the CRP and draw an activity plan for completion of the project.

2.2. The Meeting

Dr. Jean Sibiri Zoundi, Director of Research and Development of INERA, who explained the mandate and role of the organization on sustainable development of Burkina Faso, formally opened the meeting.

On behalf of the IAEA and FAO, Dr. F. Zapata welcomed the participants and thanked the host Government and INERA for the local organization of the meeting. In his introductory remarks Dr. Zapata made an account of the background and past activities of the CRP, in particular the first and second RCM and presented the objectives and program of the meeting. Dr. Bado in turn made remarks about local arrangements for the meeting.

Two and a half days consisted of technical sessions, with presentations by all the participants. One full day was devoted to a field excursion to the savannas of Africa and the last one and a half day to group development and discussion sessions on the future activities to complete the CRP and a final session with conclusions and recommendations. The agenda of the meeting is given in Annex B.

Presentations The RC holders presented their research results obtained during the reporting period highlighting the progress made along the main areas of research of the project, i.e. identification of adapted genotypes, amelioration of acidity and infertility and development of improved soil management practices for sustainable crop production in tropical acid soils. The presentations by the RA holders (or representatives) focused on identification and characterization of aluminium-resistant and P-efficient plant genotypes; and soil, crop and nutrient management practices to ameliorate soil acidity and infertility of tropical acid soils. The Technical contractor reported on studies carried out using P-33 isotopic techniques to measure P acquisition from different pools by genotypes of rice, soybean and cowpea that are reported to differ in P-efficiency, with the aim of identifying P efficiency mechanisms. The results

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obtained so far were thoroughly discussed after each presentation. Abstracts from the presentations are given in Annex C.

Field Excursion On Wednesday 20 August 2003, a field visit was made to the INERA experimental station at Saria and the villages of Saria, Nandiala and Manega. A long- term experimental field for the improvement and maintenance of the soil fertility under several crop rotations was visited at the INERA station at Saria and the results obtained so far explained by Dr. Moussa Bonzi. Farmer’s fields were also visited and the constraints and potential improvements were discussed with the farmers. The field visit provided an insight on the main biophysical and socio-economic constraints for the sustainable development of the savannas of West Africa region, and the approaches/strategies followed to overcome them at both research and small-scale farm level. Discussions focused on the need to address land degradation issues and socio-economic constraints to promote sustainable agricultural development.

Special lectures To complement the presentations on the savannas of West Africa, Drs. Laurent Sedogo and Jules Bayala, two local scientists participating in the IAEA regional TC project RAF/5/048 “Combating desertification in the Sahel” were invited to deliver lectures on the assessment of land degradation in Burkina Faso and the role of trees in the savannas of Burkina Faso respectively.

The FAO/IAEA Tropical Acid Soils Dr. Zapata, the scientific secretary reviewed the logical framework of the project, the main topics of investigation, target cropping systems and the expected outputs of the project. In accordance with the objectives of the meeting, overall progress in implementation of the project was assessed. Results are summarized in Table 1. It was noted that that the work plan of the project is in advanced stage of implementation and the results have been published and/or presented as communications in scientific meetings.

The RCM enabled a comprehensive review of work done so far and an assessment of the individual progress made by each contractor. From the examination of the studies, it was found that studies conducted by most contractors focus on amelioration of acidity and infertility of tropical acid soils.

The integrated approach to crop, and soil, water and nutrient management (SWNM) in predominant cropping systems of the savannas of Africa and Latin America has been adopted. Complementary studies for further integration were discussed and agreed to.

In addition to the technical aspects, administrative procedures that are handled by the Contract Administration Section (Mr. J. Reed) were briefly reviewed. Points of discussion included: Meeting deadlines for contract renewals and arrangements for RCMs (travel, reports, summaries), reporting system, publications of results, final evaluation the project, and supportive services.

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Group development and discussion sessions At a later stage of the meeting, participants divided in three working groups (Savannas of Africa, savannas of Latin America and supportive research) reviewed their work plans and identified activities for completion of their individual work plans. They then made presentations on the updated work plans and provided recommendations for completion of the CRP (Annex D).

Final session Final issues for completion of the updated CRP, including the preparation of final reports and manuscripts for the CRP publication were discussed (See Table 2). Detailed information (printed material) was distributed to the participants. Finally, conclusions and recommendations were drafted, presented and adopted. Prof. Hamidou Boly, Director General of INERA, formally closed the meeting.

3. CONCLUSIONS AND RECOMMENDATIONS

During the final session of the meeting, the participants formulated the following conclusions and recommendations:

(1) The objectives of the meeting were successfully achieved. Overall, progress made in implementation of the CRP is satisfactory.

(2) The data generated so far by the participants should be synthesized and published in scientific journals as well as presented in scientific meetings. Due acknowledgement should be given to the IAEA for work done under contract.

(3) The data required for the creation of suitable databases to run the selected models should be properly collected and attached as annex to the progress reports.

(4) The fourth and final RCM will be held in Vienna, Austria, 15-19 November 2004. (5) Dr. Felipe Zapata should be charged with the termination of the RCP including the

appropriate publication of the results regardless his contractual status within IAEA. (6) IAEA should continue to support long-term field experimental approaches dealing with

the analysis and development of sustainable cropping systems on acid, infertile soils of the tropical savannas.

(7) A new CRP should be initiated by IAEA on the “Development of germplasm adapted to acid, infertile soils, particularly P-efficient, N-efficient, and Al-resistant” in a concerted effort of Plant Nutritionists, Plant Breeders, and Plant Molecular Biologists.

ACKNOWLEDGEMENT

The “Institut de l’ Environnement et de Recherche Agricole” (INERA) of Burkina Faso (INERA) should be commended for accepting to host the meeting. Special thanks are given to Dr. Vincent Bado for the excellent local arrangements and organization of the meeting.

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Table 1. SUMMARY.

STUDIES CONDUCTED BY CRP PARTICIPANTS, PERIOD 1999-2003.

Participant Cropping system/locations Experiments Main type studies using NT Publications/Communications

S. URQUIAGA

(Brazil)

Maize/ Soybean / green manure and several soybean-based rotations

Five locations Cerrado (Planaltina, Uberlandia, Passo Fundo, Londrina, Dorados)

Field experiments

Amelioration acidity and infertility

C and N cycling and dynamics Conventional and zero tillage

8 papers,

13 communications

T. MURAOKA

(Brazil)

Maize/millet/Crotalaria

(no till system)

Maize/soybean

Two locations Cerrado

Greenhouse experiments

Field experiments

Corn, several plant species

Amelioration acidity and infertility (N fertilization /N supply from GM/

P utilization from DAPR)

2 papers,

3 communications

A. GARCIA

(Cuba)

Ferric Luvisol, P fertility status

Common bean/Maize Two locations

Laboratory studies

Greenhouse and field experiments

Soil P status P-32 IEK

Amelioration acidity and infertility (Liming, N and P management)

2 papers (submitted)

11 communications

5

M. LOPEZ

(Venezuela)

Sorghum/legumes

One location

Greenhouse exp.

One long term field experiment and isotopic field studies

Genotypic differences

Amelioration infertility (N fixation and fertilizer balance)

V. BADO

(Burkina Faso)

Long term experiment

Sorghum-based crop rotations.

2 locations

Field experiments Legume species and cowpea BNF/acid tolerance genotypic differences

Amelioration acidity and soil fertility, N cycling studies

One main publication

(Ph.D. thesis)

E. IWUAFOR

(Nigeria)

Crop rotation soybean/maize

Greenhouse exp.

On farm field experiments

Legume genotypes adapted to acid and low P soils

BNF and Fertilizer N management

HOUNGNANDAN

(Benin)

On farm trials crop rotation maize/soybean

Greenhouse exp.

Field exp.

Soybean cultivars BNF

Amelioration acidity/infertility

N cycling studies (fert.N recovery/N supply residues to maize and N fixation soybean)

PENA CABRIALES

(Mexico)

Greenhouse experiments.

Genotypic diff. N and P nutrition sorghum transgenic lines

Microbial studies in maize and

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Maize/legume association and rotation

Field experiments

legumes

Amelioration infertility (N and P nutrition/ fertilization)

P. J. RANDALL

(CSIRO)

Plant species/ Crop genotypes differences in P use efficiency

Greenhouse

experiments

Mechanisms of P use efficiency

W. HORST

(UH)

Plant species and genotypic differences in Al-resistance and P efficiency

Greenhouse experiments Screening methods for Al resistance and P use efficiency studies in maize and common bean

VANLAUWE/

BATIONO

(TSBF/CIAT)

Several cropping systems across Africa

Field experiments

Soil, nutrient and crop management practices to combat acidification

DIELS/

ABAIDOO

(IITA)

Legumes in tropical acid soils Lab/Greenhouse/field

experiments

P use efficiency studies

CHIEN/BOWEN

(IFDC)

Upland rice/soybean

Greenhouse exp. P sources / liming interactions

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Table 2. FINAL ISSUES OF THE CRPFinal contract renewals (extension R3)

Complete experimental work by July 2004.

Final RCM, Dates and venue: November 2004, Vienna??

Final report of each participant (Account of all work done).

Includes

*full characterization of soil and climatic conditions, *an executive summary and

*list of publications/communications

Required for closing CRP and final outstanding payments

Final report of the CRP Final list of publications of the participants Follow-up of the project????

Final Publication (s) of the CRP: IAEA TECDOC / special issue scientific journal / Both

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Annexes

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ANNEX I. LIST OF PARTICIPANTS

Third Research Co-ordination Meeting of the Co-ordinated Research Project on “The Development of Management Practices for Sustainable Crop Production

Systems on Tropical Acid Soils Through the Use of Nuclear and Related Techniques” 311-D1-RC-810.3

Ouagadougou, Burkina Faso, 18 – 22 August 2003

Research Contractors

Dr. Pascal Houngnandan BEN-11874-RB Faculté des Sciences Agronomiques Université d’Abomey-Calavi 01 BP 526 Recette Principale Cotonou - République du Bénin Tel: 00229 42 20 85 / 00229 36 08 26 (private)/ 00229 36 01 26 (office) Fax: 00229 36 01 22 Email: phoungnandan@yahoo.com

Dr. Segundo Urquiaga BRA-10953/RB EMBRAPA, Agrobiologia CP 74.505, Km 47, Estrada Antiga Rio – Sao Paulo Seropédica 23851-970 Rio de Janeiro - Brazil Tel: 5521-2682 1500 Fax: 5521-2682 1230 Email: urquiaga@cnpab.embrapa.br

Dr. Takashi Muraoka BRA-10954/RB Centro de Energia Nuclear na Agricultura (CENA) University of Sao Paulo Soil Fertility Laboratory Avenida Centenario, 303 Caixa Postal 96 13400-970 Piracicaba, SP - Brazil Tel.: +5519 34294600 (CENA); +5519 34294720 (of.-direct) 34227231 (res.) Fax: +5519 34294610 Email: muraoka@cena.usp.br

Dr. Boubié Vincent Bado BKF-10952/RB Institut de l’Environnement et de Recherche Agricole Programme Gestion des Ressources Naturelles de l’Ouest Station de Farakôba BP 910, Bobo-Dioulasso, Ouagadougou - Burkina Faso Tel.: (226) 97 33 78 (ofc)/(226) 97 46 77 (res.) Fax: (226) 97 01 59 Email: Vincent.Bado@coraf.org

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Dr. Aurelio Garcia CUB-10956/RB Instituto de Suelos Fertilidad del Suelo y Nutrición de Plantas Estacion Experimental “La Renee” Autopista Costa-Costa y Ant. Carretera de Vento C.P. 10800, Capdevila, Boyeros Ciudad de La Habana - Cuba Tel: (537)-451166; (537) 2679406 (res.) Fax: 0043 1 877 81 98 30 (c/o Cuban Mission in Vienna) Email: larenee@ceniai.inf.cu Email: ecologia.ies@ama.cu

Dr. J.J. Pena-Cabriales MEX-10959/RB Centro de Investigacion y de Estudios Avanzados del IPN, U. Irapuato Km 9,6 Lib. Norte de la Carretera Irapuato-Leon Apartado Postal 629, Irapuato, Gto., C.P. 36500 Mexico Tel: +52-462 6239600 Ext. 642 Fax: +52-462 6239642 Email: jpena@ira.cinvestav.mx

Technical Contractor

Dr. Peter J. Randall AUL11244/R1 CSIRO, Division of Plant Industry GPO Box 1600 Canberra, ACT 2601 Australia Tel: +61 2 6246 4911 Fax: +61 2 6246 5000 Email: Peter.Randall@csiro.au

Research Agreements

Dr. Walter Horst GFR-10957/CF Institute for Plant Nutrition University of Hannover Herrenhaeuser Strasse. 2 D 30419 Hannover - Germany Tel: (495 1) 7622626 Fax: (495 11) 7623611 Email: horst@pflern.uni-hannover.de Dr. Andre Bationo (Instead of Dr. Bernard Vanlauwe) KEN-11804/CF Tropical Soil Biology and Fertility Institute of CIAT (TSBF-CIAT) C/o ICRAF, Gigiri UN Avenue, P.O. Box 30677

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Nairobi - Kenya Tel: +254 2 524755/54 Fax: +254 2 524763/64 Email: A. Bationo@cgiar.org

Dr. Robert Abaidoo (Instead of Dr. Jan Diels) NIR-11135/CF International Institute of Tropical Agriculture, Ibadan, Nigeria International mailing address: IITA, c/o Lambourn Carolyn House 26 Dingwall Road Croydon CR9 3EE - United Kingdom Tel: +234 2 241 2626 Fax: +234 2 241 2221 Email: R.Abaidoo@cgiar.org

Dr. Walter Bowen (Instead of Dr. Sen H. Chien USA-10961/CF Research and Development Division International Centre for Soil Fertility and Agricultural Development (IFDC) P.O. Box 2040 Muscle Shoals, Alabama 35662 United States of America Tel: 001 256 381-6600 Fax: 001 256 381 7408 Email: wbowen@ifdc.org

Scientific Secretary:

Dr. Felipe Zapata Soil and Water Management & Crop Nutrition Section Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture P.O. Box 100 Wagramer Strasse 5 A-1400 Vienna - Austria Tel: +43 1 2600-21693 Fax: +43 1 26007 Email: F.Zapata@iaea.org

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ANNEX II. AGENDA

TROPICAL ACID SOILS CRP (D1.50.06) THIRD RESEARCH CO-ORDINATION MEETING

INSTITUT NATIONAL DE L’ENVIRONNEMEN ET DE RECHERCHE AGRICOLE (INERA), OUAGADOUGOU, BURKINA FASO

18-22 AUGUST 2003 Monday 18 August

08:30 Participants’ registration. Administrative arrangements (V. B. Bado) 09:00-9:30 OPENING Session

Opening address and Welcome address (INERA and IAEA Representatives) 9:30-10:30 Introductory Remarks (F. Zapata) 10:30-11:30 Tea break/Change of money 11:30-12:30 Session I : Savannas of Latin America : South America.

Chairperson: P. Randall 11:30-12:30 Nitrogen dynamics in crop rotations under conventional and zero tillage systems in Brazilian Oxisols. Segundo Urquiaga (Brazil)

12 :30-13:00 Discussion

13:00-14: 00 LUNCH BREAK 14:00-17:00 Session II: Savannas of Latin America : Caribbean and North

America. Chairperson : W. Bowen 14:00-15:00 Improvement of fertility and productivity of acid soils of Cuba. Alvaro Garcia (Cuba) 15:00-15:30 Tea break 15:30-16:30 Use of Nuclear Techniques in Studies on Soil Productivity in the Savannah from Tabasco State, Mexico. J.J. Pena Cabriales (Mexico) 16:30-17:00 General discussion on presentations Sessions I and II. Facilitators: Chairpersons 19: 00 Welcome Reception

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Tuesday 19 August 09:00-13:00 Session III : Savannas of Africa.

Chairperson : A. Bationo 09:00-10:00 Groundnut and cowpea effects on nitrogen availability in a weakly

acid Ultisol and nitrogen recovery by sorghum in legume/sorghum rotations. Vincent B. Bado (Burkina Faso)

10:00-10:30 Tea break 10:30-11:30 Response of soybean to N fertilizer and organic amendment and its

effect on subsequent maize grown on "Terre de barre" soil in the centre of Benin. Pascal Houngnanadan (Benin)

11:30-12: 30 General discussion on presentations of Session III. Facilitator: Chairperson 13: 00-14: 00 LUNCH BREAK 14:00-17:00 Session IV : Savannas of West Africa.

Chairperson :V. Bado. 14:00-15:00 Assessment of land degradation in Burkina Faso M. Sedogo (CNEDD, MECV) 15:00-15:30 Tea Break 15:30-16:30 Understanding the role of trees in the savannas of Burkina Faso J. Bayala (INERA) 16:30-17:00 General discussion on presentations of Session IV Facilitator: Chairperson

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Wednesday 20 August FIELD EXCURSION Coordinators : Dr. Vincent Bado and Dr. Marcel Bonzi 8:00 Departure from the hotel 08:00-9:00 Trip to Saria 09:00-10:30 Introduction (Director of the research station of Saria) Visit to long –term fertilization experiment: Study of the soil fertility

maintenance under crop rotations. 10:30-11:30 Visit to small holders in the villages of Nandiala and Saria 11:30-13:00 Trip to Manega 13:00-13:30 Lunch Break 13:30-16:00 Local field visit 16:00-17:00 Return to Ouagadougou Thursday 21 August 08:30-13:00 Session V: Supportive research work. Chairperson : S.Urquiaga

09:00-10:00 Improving soil fertility management of Cerrado (Savannah) through

the use of nuclear and related techniques. Takashi Muraoka (Brazil) 10:00-11:00 Identification and characterisation of aluminium-resistant,

phosphorus-efficient plant genotypes adapted to tropical acid soils. Walter Horst (Germany).

11:00-11:30 Tea/Coffee break 11:30-12:30 Using radioisotopes to measure phosphorus (P) acquisition from

different P pools in the soil by plants genetically modified for improved P-acquisition efficiency. Peter Randall (CSIRO, Australia).

12:30-13 :00 Discussion on the presentations 13:00-14:00 LUNCH BREAK

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14:00-17:00 Session VI : Supportive research work (Cont.) Chairperson : J.J. Pena Cabriales.

14:00-15:00 Effect of Lime on Crop Response to Phosphate Sources Varying in

Solubility. Walter Bowen and S.H. Chien (IFDC, USA). 15:00-16:00 Soil and crop management strategies to mitigate soil acidification of

Alfisols in West Africa. A. Bationo and B. Vanlauwe (TSBF/CIAT, Kenya).

16:00-16:30 Tea Break 16:30-17:30 Improving phosphorus availability in cropping systems in Sub-

Saharan Africa. R. Abaidoo in lieu of J. Diels (IITA, Nigeria) 17:30-18:00 General discussion on presentations of Sessions V and VI Facilitators : Chaipersons Friday 22 August 08:30-14:00 Session VII : Final session. Conclusions and recommendations.

Chairperson : W. Horst 08:30-09:30 Overall Assessment of progress made in accordance with work plan

and objectives of the CRP.F. Zapata 09:30-10:30 Group development session: Participants divided in three groups

develop detailed plans for completion of CRP activities. Group A : Savannas of Latin America (Rapporteur : Urquiaga) ; Group B : Savannas of Africa (Rapporteur : Bado); Group C : Supportive research : Progress and future outlook (Rapporteur : Horst).

10:30-11:00 Tea Break 11:00-12:30 Presentations of reports of the working groups 12:30-13:30 Conclusions and recommendations. 13:30 CLOSING Session (Representatives of INERA and IAEA). 14:00-15:00 Lunch break Afternoon Individual consultations

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ANNEX III. ABSTRACTS

Evaluation of selected soil and nutrient management practices to improve the fertility and productivity of acid soils of Cuba

Aurelio García Altunaga

The grain legume common bean (Phaseolus vulgaris L.) is the most important protein source for the Cuban population, although yields are generally low in different production systems because of insufficient water supply, nitrogen (N) and phosphorous (P) deficiencies and soil acidity, among other soil constraints. Soil P status can be improved by the application of local phosphate rock (PR)-based products, like partially solubilised PR (PSPR) that are natural resources locally available, cheaper and environment-friendly. On the other hand, common bean is a legume that contributes to cropping sustainability through their ability for biological N2 fixation, but this process requires additional P supply for optimal plant growth and nodule formation and function. A possible strategy would be to select common bean genotypes with better P acquisition from sparingly soluble soil and fertilizer source (PR and PSPR) and thereby increase and maintain the bean productivity and biological N2 fixation with moderate levels of P inputs. Moreover Ca requirements by legumes are also relatively high. Thus soil liming can be considered as a practice that can improve further the sustainability of the common bean production system. The application of lime may interfere on the PR dissolution and P availability. There is little information on these interactions in the literature. Several of these aspects were investigated in laboratory, glasshouse and field experiments during the last reporting period.

In a laboratory experiment using the P-32 isotopic exchangeable kinetic method it was found that the PR based - product, called C40 (PR from Trinidad de Guedes Cuban ore partially solubilized at 40 % with H2SO4 + mono ammonium phosphate) improved soil P availability and soil P dynamic parameters when the soil is limed.

In a glasshouse experiment using the P-32 isotopic dilution method, it was demonstrated that the PSPR (PR from Trinidad de Guedes Cuban ore partially solubilized at 50 % with H2SO4) was as effective as single super phosphate (SSP) for common bean and doses between 0.96 and 1.44 kg of PSPR - depending of the common bean genotype - are equivalent to 1 kg of SSP.

Results from another glasshouse experiment showed that the maize cultivar P18 should be preferred to R28, as subsequent crop to common bean cultivation, because P18 had higher utilization of residual N and did not require additional N fertilizer application.

In the field experiment significant differences were found regarding the response of common bean genotypes to soil liming. The applied doses were 15 kg N ha-1 and 2700 kg calcium carbonate ha-1, respectively and the seeds were inoculated with Rhizobium. The seven common bean genotypes tested increased grain yield due to soil liming. The economic profit in the liming treatments ranged between 1243.29 USD ha-1 (BAT 304) and 158.08 USD ha-1 (DOR 364), while without liming was between 553.68 USD ha-1 (BAT 304) and 84.25 USD ha-1 (DOR 364).

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Effect of Lime on Crop Response to Phosphate Sources Varying in Solubility

S. H. Chien and W. T. Bowen

Phosphate (P) fertilizers and lime are often required for sustainable crop production on tropical Ultisols and Oxisols because of low available P and potential Al and Mn toxicity in these soils. Both inputs, however, are costly to crop growers, especially to resource-poor farmers in the tropics. Use of alternative P fertilizers such as indigenous phosphate rock (PR) or partially acidulated PR (PAPR) rather than the use of conventional water-soluble P fertilizers may be a more cost-effective means of supplying P under these conditions. Although a considerable amount of research work has been conducted on the use of PR and PAPR, little research has been conducted to investigate the effect of limestone applications on the agronomic effectiveness of PR and PAPR. Since liming is frequently practiced for acid Ultisols and Oxisols in the tropics, there is a need to investigate the interaction of lime and PR or PAPR for crop production.

The objective of the present study was to determine the effect of liming on the relative agronomic effectiveness (RAE) of three P sources varying in water and citrate solubility for cereal and legume crops grown for three consecutive years in the greenhouse. Three P sources were used in the study: a highly reactive unground, as received Sechura PR (Peru), a granular PAPR produced from a medium-reactive Huila PR (Colombia) partially acidulated with H2SO4 at a 50% level, and a commercial-grade granular triple superphosphate (TSP). An acid Hartsell soil (Ultisol) with an original pH of 4.8 was limed to a pH of 5.6 and 6.6, providing three soil pH levels. Phosphorus was then applied to each pH treatment at rates of 0, 25, 75 and 150 mg P kg-1 of soil. Upland rice and soybean were grown during the first year followed by only upland rice in the second year. This paper reports on results for the first two years of the study.

Results after the second year of the study are summarized as follows:

1. For the first upland rice crop, Sechura PR was less effective than TSP across all soil pH levels, decreasing in agronomic effectiveness as lime rate and soil pH increased. This relationship changed, however, for the second upland rice crop (following upland rice) as the residual P effect of Sechura PR was as good or better than TSP across all lime rates. Huila PAPR was less effective than both Sechura PR and TSP for the second upland rice, although it was more effective than Sechura PR at the highest lime rate in the first upland rice.

2. Liming significantly decreased the effectiveness of Sechura PR for first-year soybean. The RAE (relative to TSP) decreased from 85% to 65% to 5% as soil pH increased, respectively, from 4.8 to 5.6 to 6.6. The effectiveness of Huila PAPR remained relatively unchanged for the second crop of upland rice after upland rice or soybean. For upland rice after soybean, however, Sechura PR was as effective as TSP in increasing grain yield and was more effective than Huila PAPR.

3. Upland rice following soybean responded more to urea as a source of N than decomposing soybean residue containing an equivalent amount of N. The availability of N from the incorporated soybean residue was minimal probably due to a moderately high C/N ratio.

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Results thus far show that a highly reactive indigenous PR such as Sechura PR can be an important source of P for sustainable crop production on tropical acid soils, having both immediate and residual effects on increasing yield. Nevertheless, the effect of liming on the agronomic effectiveness of PR should also be carefully monitored since liming can significantly reduce the initial effectiveness of PR. The use of potentially more cost-effective P fertilizers such as Huila PAPR can also be an alternative P source to water-soluble P fertilizers such as TSP for these types of soils. Its RAE ranged from 80% to 91% of TSP for soybean and upland rice across all lime rates and resultant soil pH levels.

Groundnut and cowpea effects on nitrogen availability in a weakly acid Ultisol and nitrogen recovery by sorghum in legume/sorghum rotations

Dr. B. V Bado, A. Bationo, F. Lompo and A. Sawadogo

The effects of cowpea (Vigna unguiculata) and groundnut (Arachis hypogea) on succeeding sorghum and cotton yields are studied in a long term long experiment, which started in 1993 on a weakly acid Ultisol. A factorial design in a split plot arrangement with four replications using crop rotations as first factor and fertilizers as second factor were used. In a second experiment carried out since 2000, biological nitrogen fixation (BNF), the effects of the two legumes on a succeeding sorghum yields, N recovery and nematode infection were measured. A 4x6 factorial experiment with 4 rotations as first factor and 6 fertilizers as second factor in a split plot arrangement with 4 replications was used. N fertilizer equivalencies of groundnut and cowpea were measured over two years (2001-2002). In a fourth experiment, the effects of dolomite on BNF by ten varieties of cowpea were measured in a weakly acid Ultisol. All field agronomic experiments were carried out at the agronomic research station of Farakô-Ba, located in the North Guinean zone of Burkina Faso.

The results showed that the precedent legume crops had significant effects on the succeeding sorghum and cotton yields. All the two legumes significantly increased the succeeding sorghum yield compared to the continuous sorghum cultivation. Cowpea was the most efficient on the increase of succeeding sorghum yield. Legume-sorghum rotations increased sorghum grain yield from 60 to 300 % compared to continuous sorghum. Groundnut fixed 8 to 23 kg N ha-1 and the percentage of N derived from the atmosphere varied from 27 to 34 %. Cowpea fixed 50 to 115 kg N ha-1 and the percentage of N derived from the atmosphere varied from 52 to 56 %. Compared to the mineral NPK fertilizer alone, the legumes fixed more nitrogen from the atmosphere when phosphate rock (PR), dolomite or manure was applied with mineral fertilizer. Compared to continuous sorghum, legumes-sorghum rotations increased sol mineral nitrogen and N absorption by sorghum. In continuous sorghum, fertiliser N use efficiency (NUE) was 20%, but in cowpea-sorghum and groundnut-sorghum rotations, NUEs were 28 and 37% respectively. Compared to continuous sorghum, cowpea-sorghum and groundnut-sorghum rotations provided more nitrogen to sorghum. The N fertilizer equivalency of groundnut (35 kg N ha-1) was higher than those of cowpea (25 kg N ha-1), indicating that using these legumes like precedent crop may involve an economy of 25 to 35 kg N ha-1 in mineral fertilizers.

Local varieties of cowpea fixed less N (4 to 8 kg N ha-1) from the atmosphere compared to the improved varieties (6 to 37 kg N ha-1) and dolomite didn’t significantly affect biological nitrogen fixation (P> 0.05). A more accurate measurement of BNF was obtained by the N-15

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isotopic dilution method. However, a significant correlation (P<0.05) was observed between the values obtained by the two methods (total N difference and isotopic). Groundnut decreased soil and sorghum roots infection by nematodes but cowpea increased nematode infection. Key words: Fertilizer, Nitrogen, Legume, Biological Nitrogen Fixation, Crop Rotation

Response of soybean to N fertilizer and organic amendment and its effect on subsequent maize grown on "Terre de barre" soil in central Benin

Pascal Houngnandan

There is a need to develop technologies such as improved residue management and N-fixing grain legumes, which will enable most farmers in the sub-Saharan Africa to manage better their scarce resources, regenerate their land and raise the productivity of the maize-grain legume systems in a sustainable manner. In the study area located in central Benin, soils are highly degraded due to their long occupation and cultivation over the last 300 years. Various grain legumes (groundnuts, bambara nuts, cowpea, beans etc…) cultivated now by the farmers do not show any symbiotic and good agronomic performance and also beneficial effects on soil fertility improvement in the area. Their growth and establishment on these soils are still possible but they continue to exhaust soil nutrients especially nitrogen, phosphorus and potassium without contributing anymore to their replenishment. With the increase of population pressure, agricultural intensification in these degraded soils becomes a serious threat to food security in the area. In this context, nutrient inputs must be applied to obtain good growth and adequate yield of grain legumes and their beneficial effects on soil fertility status and subsequent crop yields. Studies were carried out during the period 2001-2003 in farmers’ fields at Adingningon, southern Benin to assess the response of soybean cv TGX 1448 2E to the application of N fertilizer, chicken manure and rhizobial inoculation and their contribution to maize production planted on rotation. A basal application of 30 kg P2O5 and 30 kg K2O was given to all plots, at the starting of the experiments in 2001. Treatments included (i) soybean + 0N; (ii) soybean + 20N; and soybean + chicken manure; a fourth treatment was planted with maize and was used as reference crop to assess BNF of soybean and they were replicated in 21 farmers’ fields. In 2002, maize crop was grown on the plots of 2001 to assess the residual benefits of soybean while 15 new farmers’ fields were chosen and received the following treatments: (i) soybean + 20N; soybean + 100N; and (iii) soybean + 20N + Bradyrhizobium inoculation. Two others plots were grown with maize fertilized with 20 kg N and 100 kg N ha-1 respectively and these plots were used as reference plots to measure nitrogen fixation of soybean. In 2003, maize was grown on these plots.

In both years 2001 and 2002, nodulation, biomass production and N accumulation of soybean were not affected by the application of 20 kg N when soybean was uninoculated in 2001 or inoculated in 2002. However, the inoculation treatment produced the highest nodule number and nodule weight in 2002. The highest values of biomass production and N accumulation were found with soybean that received manure in 2001 and 100 kg N ha-1 as urea in 2002 but this was dependent on the farmer’s field. The highest biomass and N accumulation in 2001 was 1600 kg ha-1 and 41 kg N ha-1 at 12 weeks after planting with soybean that received chicken manure. The basal application of P and K followed by the slight increase of N level application in 2002 contributed to improve the biomass production at harvesting time that averaged 2570 kg ha-1. The corresponding values of N biomass and N grain yields of soybean

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averaged respectively 25 and 64 kg N ha-1. The mean value of percentage of N derived from atmosphere ranged from 12 to 68% amounting on average from 3 to 26 kg N ha-1. These values are too low indicating that soybean cultivated in the study area is far from satisfying its N requirements through N fixation. The N balance calculated on the basis of the amount of N fixed removed in N seeds is negative (-48 kg N ha-1). In the season 2002 it was observed that the contribution of soybean plots that received previously 20 kg N to the maize growth did not show any significant difference from the plots that received previously soybean + 0 N. Significant increases occurred only when plots were previously grown to soybean and fertilized with poultry manure (4999 kg DM ha-1 for maize shoot and 2311 kg DM ha-1 for maize grain). The contribution of soybean to maize yield was not significantly different from the contribution of maize-to-maize in 2002. Further investigations are required to identify soybean varieties with better agronomic performance in the study area.

Improving soil fertility management of Cerrado (Savannah) through the use of nuclear and related Techniques

T. Muraoka

The Cerrado (savannah) region has been the main agricultural expansion area in Brasil, because it has several favorable characteristics, but also limitations to crop production, mainly low soil P and N contents. Corn is the main crop (followed by soybean) in terms of cultivated area for grain production in Cerrado, and also responsible for the consolidation of no-till system in the region.

The following experiments were conducted during the period 2002-2003: a) Nitrogen fertilization of corn in a Central Cerrado soil

The objectives of this field experiment were to: a) establish an optimum N fertilizer rate (120, 150, 180 and 250 kg N ha-1) for corn crop, and b) evaluate the fertilizer N use efficiency on an Oxisol of Central Brazilian Cerrado, as affected by split application (0, 30 and 45 days). 15N labeled urea was utilized. Brachiaria ruziziensis was sown as cover crop after corn harvest. 15N labeled Brachiaria and corn plants were produced for follow up experiment. Main conclusions: a.) It is not recommendable to apply more than 30 kg N ha-1 at seeding; b) Application of 90 kg N ha-1 at 30 days after seeding supplied the N needs of the crop. Above this rate, the N utilization by the corn crop does not increase; c) the efficiency of top-dressed fertilizer N utilization depends on the rate of N applied at the previous stage; d) Increasing the rate of N fertilizer did not affect the P utilization by corn crop.

b) Improving phosphate rock phosphorus utilization by corn crop, mixing with triple superphosphate, in a Cerrado soil

The objective of this pot experiment was to evaluate the effect of triple superphosphate (TSP), when applied mixed with phosphate rock (PR), on PR phosphorus utilization by corn plants, in an Oxisol of the Cerrado region. The experiment consisted of the following treatments (the values are the P rate in mg kg-1 soil): T1 : Control; T2 : 50 TSP; T3 :100 TSP; T4 :200 PR; T5 : 400 PR; T6 : 800 PR; T7 : 50 TSP + 200 TSP; T8 : 50 TSP + 400 PR; T9 : 50 TSP + 800PR; and T10 : 100 TSP + 400 PR. Granular TSP (18.13 % water soluble P) and finely powdered Patos PR (10.53% total P and 1.76% P soluble in 2% citric acid) were applied, according to the treatments, in 1.5 kg soil contained in plastic pots, previously labeled with 32P (10

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MBq/pot). The following aditional treatments, with labeled TSP (TS32P), were included: T11 : 50 TS32P + 200 PR; T12 :50 TS32P + 400 PR; and T13 : 50 TS32P + 800 PR. Corn plants were grown for 40 days, and then cut for analysis. Conclusions: The combined applications of triple superphosphate with Patos phosphate rock increased the utilization of phosphorus of phosphate rock by the corn plants. However, this phosphate rock, due to its low reactivity, was little efficient as P source, even with the aid of TSP. Probably the proportion of soluble phosphate source in relation to PR should be increased to 1:1 to increase the effect of TSP on PR phosphorus utilization by the plants.

c) Utilization of urea, millet and crotalaria nitrogen by corn in southern Cerrado (no-till system)

The study is being carried out in Selviria, MS (Mato Grosso do Sul Estate), southern Cerrado, in an Oxisol (clayey distrophic red latosol), previously under Cerrado vegetation and cropped for 19 years in the conventional system of soil management and non tillage over last 3 years. The objective of this study is to evaluate the urea-15N nitrogen use efficiency by the corn crop, applied in several rates (30, 80, 130 and 150 kg N ha-1), 30 kg at seeding and 50, 100 or 150 kg at 4 or 8 leaves stage, combined or not with green manure crotalaria (Crotalaria juncea) or millet (Pennicetum americanum) grown previously. The green manure N utilization by corn plants will also be evaluated. The experiment consists of two same trials carried out in two consecutive years (2001/2002 and 2002/2003). Conclusion (first year): There was a significative interaction effect between grain yield and the cover crop (or green manure) systems. The maximum efficiency was reached with the rate of 116, 96 and 124 kg N ha-1, for fallow-corn, crotalaria-corn, and millet-corn system, respectively. The highest yield was obtained with crotalaria-corn succession, followed by fallow-corn and the lowest with millet-corn. Considering that millet-corn system is often recommended and therefore used by considerable number of farmers, it should be carefully re-evaluated, as in this trial it did not show advantage over fallow system. With regard to time of top-dreessing N fertilizer, the best was at 4 leaves stage.

Use of Nuclear Techniques in Studies on Soil Productivity in the Savannah from Tabasco State, Mexico

*J.J. Peña-Cabriales1 (Responsible), J.A. Vera-Núñez1, M.F. Nieto-Jacobo2, S. Salgado-García3, D.J. Palma-López3, L. Pastrana-Aponte4 and A. Ortíz-Ceballos5 (Collaborators)

Several studies were carried out in acid soils of the Tabasco state, Mexico with the aim to generate adequate agronomic practices and to enhance the important role of the microbial components on the sustainable productivity of the agro-ecosystem, i.e. Rhizobium, mycorrhizae, earthworms, etc. Seven experiments (four in the greenhouse and three in field conditions) are reported here. Others are still ongoing. In all cases, the soil used correspond to a typical Ultisol with a pH (4.6) classified as “strongly” acidic and low available P content (6 mg P-Olsen kg-1 soil) and N, K, Ca and Mg elements and a high Al and Fe availability. Four greenhouse experiments were conducted with the following specific objectives: a) to evaluate the capacity of transgenic lines of sorghum that overproduce citrate on the N uptake from 15N-fertilizer, b) to asses the capacity of sorghum transgenic lines on P uptake derived from phosphate rock using the 32P-isotopic dilution technique, c) to evaluate the nitrogen fixation capacity of representative native Rhizobium strains isolated from seven legume species of multiple potential use in the study area: Mucuna deeringiana (Mucuna blanca), Canavalia

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ensiformis (Frijol espada), Vigna umbellata (Frijolin), Cajanus cajan (Gandul), Dolichos lablab (Dolicos), Arachis pintoi (Cacahuatillo) and Crotalaria juncea (Crotalaria) and d) to evaluate the effect of a native tropical earthworn and Mucuna added as green manure on maize production. Three field experiments were established: a) to compare the 15N-fertilizer efficiency of the regional recommended dose (120 kg N ha-1 as urea) by five different maize genotypes (3 commercial recommended for acid soils: VS-486, VS-536, C-343, and 2 wild types: WT1 (sharp corncob) and WT2 (wide corncob), b) to evaluate the role of mycorrhizal inoculation on N yield in a selected maize genotype (VS-536) as influenced by phosphate rock applied at different rates (0, 100 and 200 kg P2O5 ha-1), c) to determine the time course of N-ase activity (acetylene reduction) and to asses the biological nitrogen fixation (BNF) potential of the symbiosis Rhizobium-legumes (species mentioned above) by 15N-isotopic dilution technique (“A”-value).

With regard to the evaluation of the transgenic lines of sorghum, no differences were observed beetwen lines tested neither in terms of the 15N-fertilizer efficiency (L8 overproducer citrate line=15 vs. Commercial genotype=18 %), nor in P uptake derived from the applied phosphate rock (L8 overproducer citrate line=22 vs. Commercial genotype=20 %). In relation to root nodule bacteria, 115 Rhizobial isolates were obtained from the different legumes. Using 12 antibiotics these isolates were grouped in 10 different patterns (approximately two patterns per legume species). Evaluations of the BNF of these representative strains are in progress. From the experiments dealing with the contribution of earthworm-green manure, the results indicate a positive effect of the earthworm plus Mucuna sp. on yield (77.7 g grain plant-1) vs. control (25.5 g grain plant-1). The evaluation of maize genotypes in field conditions showed a good agronomic performance of the VS-536 genotype of maize (2.35 Mg grain ha-1 average yield), suggesting that this genotype could be recommended for inclusion in the cropping system. The rate 100 kg P2O5 ha-1 as phosphate rock seems to be adequate for supplying P to maize crop in this savannah soil. The mycorrhizae treatment resulted in a negative effect on grain yield (-Mycorrhizae=2.7 vs. +Mycorrhizae=1.9 Mg grain ha-1). With regard to the symbiosis Rhizobium-legumes, Cajanus cajan and Canavalia ensiformis showed a better performance in terms of nodule number (C. cajan=147 and C. ensiformis=170 nodules plant-1), dry weight of nodules (C. cajan=5.27 and C. ensiformis=1.50 mg nodules plant-1), and nitrogen fixation (C. cajan= 230 and C. ensiformis= 318 kg N ha-1 cycle-1). The appropriate integration of these management practices will contribute to assess the potential of the technologies in study (Rhizobium-legume symbiosis, mycorrhizae, P-fertilization and earthworms) on the sustainable production of maize-based cropping systems, and ultimately allowing the restoration of the fertility status of these soils otherwise considered unfertile and marginal.

Using radioisotopes to measure phosphorus (P) acquisition from different P pools in the soil by plants differing in P-acquisition efficiency.

P J Randall and P J Hocking

Phosphorus (P) is a key element determining levels of agricultural production in many soils, and much effort has been devoted to understanding the P cycle in agriculture with the aim of optimising the efficiency of P use. The longer-term aim of this work is to develop improved, P-efficient cultivars and understand how to use them with appropriate fertiliser and management in cropping systems to improve yields and make better use of scarce P resources. It is known that species differ in their ability to access insoluble forms of P in soil, and that P-

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efficient species (White lupin being the classic example) are able to modify the chemistry of their rhizosphere to dissolve insoluble P and increase the P available for uptake. It has been reported that genotypes of several species differ in P efficiency. Techniques employing radioisotopes of P allow us to test the hypothesis that such genotypic differences are due to mechanisms that allow access to normally insoluble soil P pools. Answers to this question allow us to better focus research on mechanisms aimed at discovering key genes and developing screening methods for breeding of more efficient cultivars.

The current work has examined genotypes of rice, soybean and cowpea that are reported to differ in P-efficiency, with the aim of identifying P efficiency mechanisms. Labelling with 33P radioisotope was used to calculate L-values to assist the understanding of P nutrition, especially the complex questions surrounding P acquisition from different soil P pools. The 33P radioisotope technique allows testing of the hypothesis that differences in P efficiency are linked to differences in ability to access normally insoluble forms of soil P. The data for rice did not support the hypothesis, while that for soybean and cowpea was equivocal.

To further test the hypothesis, root exudates from soybean and cowpea genotypes were analysed and depletion of P by different genotypes from chemically-defined fractions of rhizosphere soil was measured. As no large genotypic differences were found, the results provide no support for the hypothesis. Some preliminary work on excess cation content of the legume genotypes will be reported but its completion awaits suitable field-grown-material.

Identification and characterisation of aluminium-resistant, phosphorus-efficient plant genotypes adapted to tropical acid soils.

W.J. Horst

In most tropical acid soils aluminium (Al) toxicity and phosphorus (P) deficiency are the most important factors limiting plant growth and crop yields. One of the key elements of sustainable cropping systems on theses soils is the integration of crops and/or crop cultivars with high Al resistance and P efficiency.

Own experimental activities in the reporting period concentrated on three aspects related to Al toxicity and resistance: (i) the development of a selection technique for Al resistance and thus adaptation to acid soils and the genetics of Al resistance in maize, (ii) the role of cell–wall characteristics in Al resistance in maize, and (iii) the characterisation of differences in Al resistance in common bean. (i) The method of the determination of Al-induced callose formation in root tips of maize was further optimised in order to be able to screen a larger set of genotypes for Al-sensitivity, a pre-requisite for the analysis of a complex diallel. The improvements achieved now allow the evaluation of a 15x15 diallel in one concise experimental setup. The statistical analysis clearly shows that the General Combining Ability (GCA) rather than the Specific Combining Ability (SCA) is of major importance for the selection criteria “Al-induced” callose formation as a indicator of Al sensitivity. Among the cultivars included into the diallel SA3, SA4, SA 7 and CMS 36 showed the best GCA for low Al-induced callose sythesis that means Al resistance. Al-induced callose formation was negatively correlated to yields on acid soils. This screening technique proved to be a powerful tool in the identification of germplasm with high combining ability for adaptation to acid Al-toxic soils.

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(ii) There is increasing evidence that cell-wall characteristics may modulate Al sensitivity. Silicon-induced amelioration of Al toxicity could be related to an “in-plant” effect. Al-treated plants accumulated higher amounts of Si in the root apical cell walls than -Al plants. From the fractionated desorption of Al from the cell-wall material it appears that the amount of the readily cell wall-exchangeable Al in -Si plants is higher than in +Si plants suggesting that Si modifies Al binding to the cell walls.

(iii) Common bean (Phaseolus vulgaris) cultivars were evaluated in nutrient solution containing a range of aluminum (Al) concentrations (0, 10, 15, 20, 50 µM) at several pH levels (6.0, 4.5 and 4.3). Effects on root-elongation rate, callose formation and Al content in root tips were determined. Root elongation was highly reduced at pH 4.3, complicating the selection of a control for the Al treatments at low pH. Increasing the Ca2+ supply to 5 mM (CaCl2) was necessary to avoid proton toxicity. Similarly, addition of K+ enhanced the root growth especially when plants were treated with Al, allowing for a better differentiation between cultivars. Despite the high Ca2+ concentration in the nutrient solution, Al-inhibited root elongation was observed at 10 µM Al supply. However, Al-induced callose formation and Al contents in root tips were highly reduced. Significant differences in root elongation were observed between 28 cultivars treated for 36 h at 20 µM Al, pH 4.5. Also, significant differences in callose formation and Al contents of root tips were observed between the same cultivars treated for 4 h at 20 µM Al, pH 4.5. However, no correlation between Al induced callose formation and inhibition of root elongation by Al was found. Moreover, Al-resistant cultivars tended to accumulate more Al in the root tips. In conclusion, in contrast to maize, in beans Al resistance seems to be related not to Al exclusion but rather to Al tolerance.

Soil and crop management strategies to mitigate soil acidification of Alfisols in West Africa

A.Bationo and B. Vanlauwe

Besides the Oxisols and Ultisols of the humid forest of West Africa, most soils in this region are Alfisols that do not have inherent aluminum toxicity problem. Under the natural vegetation of the Alfisols, it is unlikely to find highly acidified soils. This could be attributed to the general recycling of most bases through deep rooting system of the natural vegetation. It has however been reported that after continuous cultivation there is an increased acidification. Among the factors responsible for this acidification are the type of parent material, nitrate and base leaching; removal of bases with crop harvesting; use of acidifying fertilizers such as ammonium sulphate and depletion of soil organic matter combined with low applications of organic amendments.

This report will highlight the strategies to combat the acidification of the Alfisols, which cover most parts of the moist and dry savannah of West Africa. Liming not being available to many small-scale farmers in the region, strategies promoted to combat soil acidification of these soils are the application of the right type of fertilizer, organic materials like crop residue, manure and compost and legume-cereal crop rotations.

Key words: Acidification; alfisols; savannah; organic materials

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Nitrogen dynamics in crop rotations under conventional and zero tillage systems in Brazilian Oxisols

URQUIAGA Segundo (1), SISTI Claudia P.J. (2), SANTOS Henrique P. dos (3), KOCHHANN Rainoldo (3), RESCK Dimas (4), FERNANDES Francisco (5), LARA Waldo (6), ALVES Bruno J.R. (1), BODDEY Robert M. (1)

(1) Embrapa Agrobiologia, CP 74.505, Seropédica, 23890-000, RJ, Brazil. (2) Departamento de Fitotecnia, Universidade Federal Rural do Rio de Janeiro, Seropédica, 23890-000, RJ, Brazil. (3) Embrapa Trigo, CP 569, Passo Fundo, 99001-970, RS, Brazil. (4) Embrapa Cerrados, CP 08223, Planaltina, 73301-970, DF, Brazil. (5) Embrapa Agropecuaria Oeste, CP 661, Dourados, 79804-970, MS, Brazil. (6) Universidade Federal de Uberlândia, Uberlândia, MG, Brazil.

As mentioned in previous reports, in Brazilian agriculture the zero tillage (ZT) system is considered today as the best alternative to conventional tillage (CT). Preserving crop residues on the soil surface, the ZT system contributes to control soil erosion and is seen today not only as a means to contribute to sustainable agriculture, but also to mitigate the emission of CO2 to the atmosphere. In 1999 the National Centre for Agrobiology Research of Embrapa-Seropedica, started a research program in different acid soils of this country, to study the biological processes involved in the dynamics of N in the soil/plant system under different crop rotations under ZT, in comparison to CT. This project has received strong assistance from the IAEA through the research contract Nº 10953/R2, which was renewed last year. The main activities of this project are being conducted in representative acid soils located at experimental stations of different Embrapa research centres and one other collaborative institution. In continuation results of the last year are sumamrtize below. From Embrapa Cerrados (Planaltina, Brasilia), 1. In an Oxisol of the Cerrado of Brasilia, for a maize crop fertilised with 90 kg N ha-1 no significant differences were found among the effects of soil tillage systems neither on the grain yield (7 Mg ha-1) nor on the total N accumulated by this crop (161 kg N ha-1). 2. Under ZT the N fertiliser use efficiency (%N-FUE) of the maize crop was higher (54%) in comparison to the CT (46 %). Under ZT the %N-FUE did not vary with time of N application but under CT the %N-FUE was significantly lower when N was applied later. The lower value of the %N-FUE under CT could be associated with the influence of this practice on the mineralisation of the soil organic N, contributing to higher soil N availability. This effect was demonstrated by the results of the “A” value technique, which was higher under CT (246 kg Nha-1) than under ZT (218 kg Nha-1). 3. The higher values of soil N availability under CT could explain the rapid and significant decrease of the total N content of the soil profile especially in the upper layers of the soil. From the University of Uberlândia (Uberlândia, Minas Gerais State), 4. A soybean crop inoculated with Bradyrhizobium spp grown in an Oxisol yielded over 3.4 Mg ha-1 independent of the tillage system in this study (ZT and CT), and there was no significant response to the application of 60 kg N ha-1 at the flowering stage, even though the %N-FUE was high (54%). From these results it is inferred that BNF in soybean is very efficient in the Cerrado region, independent of the tillage system, and its contribution is sufficient to cover the whole N demand of this crop. The BNF significance is inversely related to the soil N availability including N fertilisation. From Embrapa Wheat (Passo Fundo, Rio Grande do Sul), 5. In the subtropical region of Brazil, the more diversified crop rotations, which included vetch as green manure and the maize crop (R2, wheat/soybean/vetch/maize; R3, wheat/soybean/ vetch/maize/oats/soybean), under ZT and CT systems, promoted a significant input of C and N to the soil via crop residues, especially under ZT, being 32% higher than the traditional crop rotation wheat/soybean (R1). Under the conditions of this study the maize crop residues contributed 14.5 to 19 Mg ha-1 of

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organic C in 13 years. The results showed also a clear and positive influence of BNF as a source of soil N. The vetch crop used as green manure in crop rotations R2 and R3 contributed with 630 and 950 kg ha-1 of N from BNF and these contributions made the great differences in these crop rotations to the input of N, being 67% higher than that of rotation R1. In general, the contribution of BNF to the soil via crop residues of legume crops (vetch and soybean) was approximately 50%. These results confirm the great importance of the quantity and quality of N-fixing crop residues as a source of organic C and N to the soil, contributing in this form to soil C sequestration. 6. During the rainy season of last year (2002) the influence of crop rotation and tillage systems on the emission of N2O and CH4 from the soil surface was evaluated in the experimental plots in comparison to the soil under native vegetation (control). Values of the emission of N2O were extremely variable but there was a clear tendency to increase significantly during the first 10 days after sowing (especially under the crop rotation soybean/wheat) to a maximum of 156 µg N-N2O m-2 h-1 under CT and 100 µg N-N2O m-2 h-1 under ZT, eventually decreasing to the level of the control soil (average of 5 µg N-N2O m-2 h-1) after this period. 7. The emissions of methane, independent of the treatments studied, were always similar to the control soil. The values varied around 10 mg CH4 m-2 day-1 from November to December 2002 and doubled from December 2002 to January 2003, and only during the first period of this study there were days on which this gas was consumed. From Embrapa Soybean (Londrina, Paraná), 8. Estimation of the underground N of soybean plants applying the traditional and the 15N leaf labelling techniques produced contrasting results, and this was greatly affected also by the age of the plants. The measurements carried out at the harvest time (120 days after sowing) using the traditional method indicated that only 2% of the whole N accumulated by this crop was in the underground part, while the 15N leaf labelling method indicated a value of 25%. These results appear to be overestimated. Even if the 15N method is a promising tool for this kind of study it needs to be improved, because from previous studies on crop rotation based on this crop it is not easy to see in the field any significant positive N balance. 9. From a survey made in 21 representative commercial areas of soybean crop from the Paraná State it was determined that the contribution of BNF to the soybean crop varied from 60 to almost 100%, and in 20% of these areas the contribution of BNF was lower than 80%, which was the same value as the mean N harvest index, and from this we may deduce that in 20% of the soybean areas evaluated, this crop is leaving a negative soil N balance. Applying a Multivariate statistical design it was found that the most limiting factors to BNF in this region are associated with the non-inoculation or poor quantity of inoculant of Bradyrhizobium spp. used, sowing in periods of low rainfall period and in the older areas under ZT. From Embrapa Western Agriculture (Dourados, Mato Grosso do Sul) 10. Evaluating the influence of crop rotations that included soybean, wheat, maize, forage rape (green manure), oats and cotton grown under ZT on the soil N availability using the “A” value technique, wheat and oats as indicator crops, it was found that the “A” values were similar for most crop rotations studied, showing only significant differences between the indicator crops, varying from 116 kg N ha-1 (Oats) to 183 kg N ha-1 (Wheat) when N was applied as ammonium sulphate. Under these conditions, the best performance of the wheat crop was associated with its better tolerance to the drought during the previous winter. This study demonstrated also that the soybean crop had a similar effect to the other crops on the soil N availability.

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Improving Phosphorus Availability in Cropping Systems of sub-Saharan Africa

R. Abaidoo et al.

Previous work to increase yields of staple cereals in West Africa had concentrated on the introduction of grain legumes in rotation with maize to provide a second cash crop and to increase soil nitrogen levels for the maize. However, a major limitation is that legume growth and nitrogen fixation is restricted by widespread phosphorus deficiency. Supplies of fertilizer P are unreliable and relatively expensive. The current research investigated the genetic route to optimize use of P in these cropping systems with the additional objectives of identifying genotypes that are better able to acquire P from soil or fertilizer sources or better able to use the P taken up, understanding and quantifying P “efficiency” character and developing tools for use in breeding programmes.

Soils from field experimental sites in West Africa have been characterised chemically (using an enhanced method to determine isotopically exchangeable P in the soil) and biologically (using P uptake by maize and P response curves) as a necessary first step for interpreting performance of the soybean and cowpea lines under study. The isotopically exchangeable P in soil, or E-value, is difficult to determine in many tropical soils with high adsorption capacities because these soils often have P-concentrations in the soil solution lower than the detection limits of the standard colorimetric methods. An enhanced method to determine the E-value, as proposed by Maertens et al. (in press), uses an anion exchange membrane (AEM) to extract the isotopically exchanged P and overcome detection limits of dissolved P in the soil solution. This method has been compared to the traditional E-value assessment for a selection of West-African topsoils and subsoils. In addition, several legume varieties are being screened for their capacity to mobilize soil phosphorus in a greenhouse experiment. Methods based on isotopic dilution (E-value and L-value determination) are used to assess P-utilization. The two E-values, Esoil solution and EAEM, were nearly equal in soils with P-concentrations in the soil solution larger than 0.01 mg P L-1. Esoil solution-values were overestimated and several times larger than EAEM-values in soils with smaller P-concentrations. As such, the enhanced method is a valuable technique to determine the E-value in soils with sparingly soluble P.

The identification and agronomic characterisation of soybean and cowpea genotypes capable of efficient use of sparingly available soil phosphorus were carried out in greenhouse studies and field trials to identify mechanisms that may explain differences between genotypes in phosphorus acquisition efficiency. The plots sown to legumes and maize in the previous season were sown to maize in the subsequent year and the yield from this cereal phase then used to evaluate rotation benefits and the role of the grain legumes in P cycling to subsequent cereal crop. The genotypes were put into four P efficiency groups (Efficient responders, Inefficient responders, Efficient non-responders, and Inefficient non-responders) based on grain yield differences between genotype means and the general means of both 0 P and the 30 kg P ha-1 treatments in all the three locations. Out of the 13 soybean genotypes, six were classified as efficient responders; two as inefficient responders; and five as inefficient non-responders while four cowpea genotypes were classified as efficient responders; one as inefficient responder; one as efficient non-responder; and two as inefficient non-responders. It appears from this initial data that the P cycling benefits through previous cowpea and soybean cultivation may not be large.

Studies of mycorrhiza infection did not significantly explain varietal differences in P efficiency character. Analysis of depletion of P in rhizosphere soil has indicated some genotypic differences, an observation that is being followed up using soil labelled with 33P to

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measure P uptake from different soil P pools. Levels of citrate exuded from roots were too low to be significant, and rhizosphere pH showed no consistent genotypic differences in short-term experiments. Excess cations measured in samples from the West African field experiments and from glasshouse experiments in Australia showed significant genotypic (and species) differences. The glasshouse data suggest a possible relationship between P content of whole plants at flowering and excess cations.

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ANNEX IV. SUMMARY OF THE EXPERIMENTAL ACTIVITIES TO BE COMPLETED BY 2004

Presentations of the Working Groups

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Working Group: Savannahs of Latin America Participants: Brazil: Dr. T. Muraoka Dr. S. Urquiaga Cuba: Dr. A. Garcia Mexico: Dr. J.J. Pena-Cabriales Summary Main activities to be developed during 2003 – 2004

Topics Experimental Activities Participating scientists

a. Soybean cultivars for high P use efficiency.

Muraoka

b. Common bean cultivars for high P use and BNF efficiency.

Garcia Pena-Cabriales

1. Plant genotypes

c. Enhancement of BNF in different legumes (Canavalia, Cajanus and Mucuna) by microbial partners (Rhizobium and VAM).

Pena-Cabriales

a. Residual effect of N fertilizers and green manure (Legumes and millet) under different crop rotations.

Takashi

b. Soil N losses (N2O and NO3) under different tillage and crop rotations.

Urquiaga

2. Cropping systems

c. Determination of the best association of three maize cultivars and three legume species previously selected for high BNF and VAM efficiency.

Pena-Cabriales

3. Amelioration of soil fertility (P fertilization)

a. Determination of the best ratio of PR-TSP to enhance PR agronomic effectiveness for maize (Greenhouse studies).

b. Determination of P rate and P sources for common bean

Takashi Garcia

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Working group: Savannahs of Africa Members: BADO Vincent (Burkina Faso) HOUNGNANDAN Pascal (Benin) Iwuafor Emmanuel (Nigeria) Summary Main activities to be undertaken in 2003-2004 Topics

Experimental activities

Participating scientists

1. Genotypes

1.1. Screening soybean cultivars for high yield and BNF in “Terre de barre” (greenhouse) and in different locations of in the derived savanna and coastal savanna in Benin (field) 1.2. Screening of cowpea varieties for adaptation to acid soil and BNF performance in Sudano- Sahelian zone in Burkina Faso (greenhouse) 1.3. Screening of legume species adapted to acid and low P soils in the northern Guinea savanna (field)

Houngnandan Pascal Bado Vincent Iwuafor Emmanuel

2.Integrated approach in cropping systems.

2.1. Nitrogen cycling in maize/soybean crop rotation (field) 2.2. Nitrogen cycling in maize/legume species crop rotation (field) 2.3. Nitrogen cycling in sorghum-based crop rotations (field) 2.4. Long term evaluation of soil fertility maintenance technologies in Sudano and northern Guinea zones (field)

Houngnandan Pascal Iwuafor Emmanuel Bado Vincent Bado Vincent

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Working Group: Supportive research (Agreement holders) Participants: W. Horst (UH); R. Abaidoo/J. Diels (IITA); P.J. Randall (CSIRO); W. Bowen/S.H. Chien (IFDC); A. Bationo/B. Vanlauwe (TSBF/CIAT). Summary of completed work and research plans for the final period 2003-2004

UH, the developed method for the screening of maize genotypes for Al resistance based on callose formation has been further improved. The study of a diallel from contrasting cultivars showed that additive gene action plays, an important role in the inheritance of Al resistance of the tested genotypes and proved to be a powerful tool in the identification of maize germplasm with high combining ability for adaptation to acid Al-toxic soils.

The application of this technique for the screening of common bean for Al resistance failed. It appears that the expression of Al toxicity and Al resistance in common beans differs from maize. Whereas Al toxicity and Al resistance in maize expresses particularly in the root apoplast, in bean the root symplast seems to play a more important role.

Future work will concentrate on the better understanding of Al toxicity and Al resistance in common bean, which is obviously a pre-requisite for the development of a screening procedure in this plant species.

Studies conducted at IITA have investigated the genetic variability in P use efficiency in cowpea and soybean genotypes for P use efficiencies in legume-cereal cropping systems leading to the identification of P response groups within cowpea and soybean genotypes. Field data have been analysed to select reliable field criteria for P use efficiency.

Future work will focus on

1. continue efforts to identify genotypes for efficient nutrient use, tolerance to nutrient toxicities as components of integrated soil-nutrient management systems.

2. use of enhanced isotopic methods to measure exchangeable P in order to overcome detection limits of P concentrations in the soil solution. It is anticipated that this work will contribute to the development of improved methods for screening legume genotypes for their capacity for P acquisition.

3. continue to screen legume genotypes for efficient use of PR.

In order to facilitate the development of P efficient cultivars to make optimum use of scarce P soil and fertilizer resources, work at CSIRO aims to identify the genes responsible and develop screening procedures based on an understanding of the mechanisms involved in P efficiency. The use of 33P labelling to determine L-values has allowed us to conclude that P efficiency in the genotypes tested (rice, cowpea and soybean) is probably not due to differences in ability to access normally insoluble P sources.

Future work will therefore concentrate on other mechanisms involving differences in root characteristics or internal redistribution of P in the plant. It will include work at the physiological and molecular levels.

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Study at IFDC: A three-year greenhouse study is underway to determine the initial and residual effect of lime on crop response to phosphate sources varying in solubility. Three P sources are being studied: a highly reactive unground, as received Sechura PR (Peru), a granular PAPR produced from a medium-reactive Huila PR (Colombia) partially acidulated with H2SO4 at a 50% level, and a commercial-grade granular triple superphosphate (TSP). An acid Hartsell soil (Typic Hapludult) with an original pH of 4.8 was limed to a pH of 5.6 and 6.6, providing three soil pH levels. Each P source was then applied to each pH treatment at rates of 0, 25, 75 and 150 mg P kg-1 of soil. To pick up possible rotation effects, an upland rice – upland rice – upland rice sequence is being compared to a soybean – upland rice – soybean rotation. Data from the first two years of the experiment show that liming significantly decreased the effectiveness of Sechura PR more for first-year soybean than for upland rice. For the first upland rice crop, Sechura PR was less effective than TSP across all soil pH levels, decreasing in agronomic effectiveness as lime rate and soil pH increased. This relationship changed, however, for the second upland rice crop as the residual P effect of Sechura PR was as good or better than TSP across all lime rates.

Future plans: The study will continue for one more year with crop yields, nutrient uptake, and long-term changes in soil acidity and nutrients and P source effectiveness to be analyzed following the full three-year period.

TSBF/CIAT: Within the frame of Integrated Soil Fertility Management, TSBF has conducted field experiments in all agro-ecosystems of Africa covering a wide range of tropical acid soils. Of particular relevance to this project is the development and testing of soil and crop management strategies to combat soil acidification of Alfisols in West Africa (reported in the meeting). As lime is not available to many small-scale farmers in the region, work will continue on strategies focusing on the application of the right type of fertilizers, use of organic materials and legume-cereal crop rotations.

Summary Table of Supportive Research

Topics Experimental activities Institutions Germplasm development Use of molecular biological

techniques in breeding and selection for Al resistance and P efficiency

UH, CSIRO

Screening techniques Al resistance of maize and beans P efficiency of soybean and cowpea

UH IITA, CSIRO

Efficiency/resistance mechanisms

P efficiency in soybean and cowpea Al resistance of maize and bean

CSIRO, IITA UH

Isotopic techniques Further refinement of techniques for use in tropical acid soils (N-15, C-13, P-32, Cs-137 and other radionuclides)

IAEA

Cropping systems Integrated soil fertility management (field experiments)

TSBF

Fertilizer technologies PR /lime interactions IFDC

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