r j AM (ScOPE Nitrogen Cycling in West African Ecosystems T. Rosswall (Editor) Proceedings of a workshop arranged by the SCOPE/UNEP International Nitrogen Unit in collaboration with MAB (Unesco) and IITA at the International Institute for Tropical Agriculture, Ibadan, Nigeria 11-15 December, 1978 Cover: Burning of savanna in Tchad Photograph by Dr. C. Christiansson Department of Physical Geography University of Stockholm © 1980. SCOPE/UNEP International Nitrogen Unit, Royal Swedish Academy of Sciences ISBN 91-7190-007-I Original produced by Suridt Offset AB, Stockholm Printed in Sweden by Rekam & Katalogtryck, IJppsala PREFACE The present volume reports on the first regionai meeting arranged by the SCOPE/UNEP international Nitrogen Unit. The volume contains invited key note papers as well as papers contributed by other participants in the workshop. A major part of the meeting was devoted to discussions of present knowledge of nitrogen cycling in three major ecosystem types in West Africa, viz., savannas, forests and agro-ecosystems. The reports from these work group discussions are included together with a report on the final dis- cussion on research priorities and future cooperation. The SCOPE/UNEP Nitrogen Unit asked L.C. Nwoboshi and N.O. Adedipe in Nigeria and P. Berg in Sweden to prepare bibliographies on published articles dealing with ni- trogen cycling in West African ecosystems. These bibliographies have been extended and are included in this volume. The meeting was financially supported by the United Nations Environment Programme (UNEP), the Scientific Committee on Problems of the Environment (SCOPE) and the Man and the Biosphere programme (MAB) of Unesco. We are very grateful for their generous support, as well as for the sponsorship of the meeting by the Nigerian national committee for SCOPE. The meeting was held at the International institute of Tropical Agriculture (IITA), and all the facilities of TITA were put at our disposal thanks to the generosity of its Director General, Dr. W.K. Gamble. Dr. A. Ayanaba served as the local organizer and the hard and efficient work of the lilA staff was a very important reason for the success of the meeting. Ms G. Sunnerstrand and Mr P. Wigren did the artwork and photography, while Ms M. Ktigesson and C. Ribbing were helpful in the editing of the volume, Mr N. Robertson was responsible for the important linguistic editing. To all those,and especially to Ms G. Sundt, who was responsible for the production of the camera-ready copy, I would like to express my gratitude. The publication has unfortunately been very delayed for a variety of reasons, and I would only like to cite Hofstadter's law: It always takes longer than you expect, even when you take into account Hofstadter's Law. Stockholm December, 1980 Thomas Rosswall Project Coordinator SCOPE/UNEP international Nitrogen Unit LIST OF CONTENTS Opening remarks T. Rosswall .................................. 7 Opening remarks W.K. Gamble ................................. 11 Joint FAOIIAEA/Federal Republic of Germany international coordinated programme of research on agricultural nitrogen residues with particular reference to their conservation as fertilizers and behaviour as potential pollutants ............................................. 13 F.P. W. Winteringham 17 The nitrogen cycle - General considerations .......................... T Rosswall Aspects of nitrogen cycling from an atmospheric chemist's point of view ....... 23 R. Söderlund Losses of plajit nutrients in runoff and eroded soil ...................... 31 R. Lal Nitrogen losses from disturbed ecosystems - ecological considerations ........ 39 P.M. Vitousek Microbiological considerations of the nitrogen dycle in West African ecosystems 55 Y. Dommergues, J.-L. Garcia and F. Ganry The nitrogen cycle in West Africa - agronomic considerations ............. 73 D.J. Greenland The nitrogen cycle - pedological considerations ....................... 83 V.N. Kudeyarov Productivity of Sahelian rangelands in relation to the availability of nitrogen and phosphorus from the soil ................................... 95 W. 1'. Penning de Vries, J.M. Krul and H. van Keulen Le cycle de l'azote dans les agro-systemes de l'Afrique de I'Ouest ............ 115 Hainnaux Farming systems of West Africa in relation to nitrogen cycling .............. 131 B.N Okigbo Nitrogen cycling in a semi-arid region of tropical Australia ................ 157 R. Wetselaar A survey of nitrogen levels in the major soils of Ghana ...................171 G.K. Asamoa Nitrogen profile in a kaolinitic alfisol under fallow and Continuous cultivation . 181 A.S.R. Juo Nitrogen fixation by blue-green algal soil crusts in Nigerian savanna .......... 191 A.O. Isichej Fixation d'azote par les lëgumineuses spontanes au Mali ................. 199 S. T Sanogho, A. Sason et J. Renaut Premiers résultats concernant I'inoculation du soja au Sénégal .............. 209 J. Wey Presence et distribution de Rhizobium japonicum et de Rhizobium cowpea dans les sols de Côte d'lvoire .................................... 215 M. Zengb A deficiency of the symbiotic nitrogen fixation in a dry tropical agrosystem the nitrogen chiorosis of groundnut (Arachis hypogaea) in Senegal ....... 221 JJ. Dreon The practicabiities of legume seed inoculation with rhizobium under Nigerian conditions ............................................ 233 S.D. Agboola Effect of tillage techniques and fertilizer nitrogen on the growth and yield of cowpeas in Sierra Leone ................................... 243 C.S. Kamara Mineral nutrition of cowpea ( Vigna unguiculata (L) Walp) ................. 249 S. Uduzei Remison The effect of molybdenum and magnesium on the growth and yield of cowpea and soybean on an acid uplanJ soil ............................ 255 E.R. Rhodes Weed control and nitrogen restoration with legumes in upland rice culture in Sierra Leone ........................................... 261 G.C. Nyoka Effects of plant density and increasing levels of nitrogen on the response and uptake of N by two maize (Zea mays L.) varieties .................. 269 F.K. Adeyefa, S.0 Remison andMC Igbokwe Nitrogen requirement of corn in a newly cleared loamy sand at Uyo, Nigeria: The effect of N fertilizer and liming materials ..................... 275 MC Igbokwe Détérmination de la fértilisation azoté de rédressement sur un sot en ouverture sous climat equatorial (Vallée du Niari, Congo) .................... 285 D. Dzaba Growth stimulation by dried poultry manure: Implications for nitrogen cycling in West African ecosystems ................................. 291 B.K. Ogunmodede The role of nitrogen oxides in oxidation of sulphur dioxide in combustion stack gases ............................................ 295 J. Pawlikowska-Czubak A re-evaluation of present concepts relating to nitrifier growth and production of nitrate in soil ......................................... 303 F. Lyman Dinkins Denitrification in a toposequence ................................. 311 A. Ayanaba and W.J. Veldlcamp The effects of fire on aspects of nitrogen cycling in Olokemeji forest reserve, Nigeria ............................................... 317 A.B. Oguntala Nitrogen loss by burning from Nigerian grassland ecosystems ............... 325 A. 0. Isichei and W. W. Sanford Effects of various rates of paraquat dichloride on nitrogen transformation in some West African acid soils ................................ 333 A.G. Agbahungba Nitrogen economy in selected farming systems of the savanna region .......... 345 L.A. Nnadi Nitrogen cycling in a teak plantation ecosystem in Nigeria ................. 353 L. C Nwoboshi Nitrogen cycling in a soil-tree system in a Sahelian savanna. Example of Acacia senegal ............................................... 363 F. Bernhard-Reversat and H. Pou pan Nitrogen and potassium balance in maize in the humid tropics .............. 371 R.A. Sobulo Nitrogen cycling in the savanna zone of Nigeria ........................ 377 A. Singh and V. Balasubramanian Utilisation de l'cngrais par les cultures et pertes par lixiviation dans deux agro- systèmes de Côte d'lvoire .................................. 393 P.F. Chabalier Report of the work group on the Sahel-Savanna zone .................... 399 W. T. Penning de Vries (rapporteur) Report of the work group on tropical forests ......................... 409 P.M. Vitousek (rapporteur) Report of the work group on agroecosystems in the wet humid tropics ........ 415 Hainnau.x (rapporteur) Research priorities and future co-operation .......................... 421 T Rosswall and P.M. Vitousek (rapporteurs) References to publications on nitrogen cycling in West African ecosystems ..... 429 P. Berg, L. C. Nwoboshi, N. 0. Adedipe and T. Rosswall List of participants ........................................... 449 T. Rosswafl (ed). 1980 Nitsogen Cycling in West African Ecosystems OPENING REMARKS T. Rosswall SCOPE/UNEP International Nitrogen Unit, Royal Swedish Academy of Sciences, Box 50005, S-104 05 Stockholm, Sweden Mr Chairman, Dr Gamble, Mr lyamabo, Ladies and Gentlemen, At a meeting between the management of UNEP (United Nations Environment Pro- gramme) and the Executive Committee of SCOPE (Scientific Committee on Problems of the Environment) of ICSU (international Council of Scientific Unions) last week in Nairobi, it was decided to prepare a joint statement, to be signed by the Executive Direc- tor of UNEP, Dr M. Tolba, and the President of SCOPE, Professor G.F. White. The state- ment will deal with the importance