Integrated Nutrient Management For Sustained Crop Production In Sub Saharan Africa A Review

'Slash and burn agriculture'remains the major food production system in sub-Saharan Africa. However, in a major part of the region, where fallow periods have been shortened below a critical level, the system can no longer sustain crop yield due to decline in soil fertility. In order to allow continuos crop production, principles and practices that mimic natural fallow and enhance soil organic matter build-up need to be integrated into new cropping systems that replace shifting cultivation or 'slash and burn agriculture'. These include (a) returning of organic materials to the soil, (b) ensuring minimum disturbance of soil surface, and (c) use of multipurpose trees and perennials. At the time, inorganic fertilizers are also needed to maintain a positive nutriente balance of the agroecosystem. On the widespread sandy kaolinitic soils in sub-Sahara Africa, numerous published results have shows that without appropiate organic inputs, inorganic fertilizer alone cannot sustain crop yield and maintain soil fertility in the long run because of soil acideification, loss of soil organic matter and compaction. The adoption of management practices that integrate organic, chemical and biological inputs into economically and environmentally sound production systems is an essential step towards sustaining high crop yields and preventing land degradation in the region. In the humid forest region, where root crops and tree crops are ecologically more suitable, agroforestry systems, such as multistory homestead gardens, plantation/crop combinations, and alley cropping, appear to have a high potencial for maintaining soil organic matter at levels adequate for sustaining crop growth. In the subhumid and humid/subhumid transition zones, crop residue mulch, minimum tillage and leguminous cover crops are promising tecnologies for improving nutrient and water use efficiency and sustaining high yields of maize, sorghum and cowpea. In the semiarid regions, however, improvement of millet and sorghum yields is severely limited by the lack of organic inputs. The potencial for increasing and sustaining food crop production in the seminarid zone ultimately depends upon successful integration of crop, fodder and fuelwood production within a farming community.

'Slash and burn agriculture'remains the major food production system in sub-Saharan Africa. However, in a major part of the region, where fallow periods have been shortened below a critical level, the system can no longer sustain crop yield due to decline in soil fertility. In order to allow continuos crop production, principles and practices that mimic natural fallow and enhance soil organic matter build-up need to be integrated into new cropping systems that replace shifting cultivation or 'slash and burn agriculture'. These include (a) returning of organic materials to the soil, (b) ensuring minimum disturbance of soil surface, and (c) use of multipurpose trees and perennials. At the time, inorganic fertilizers are also needed to maintain a positive nutriente balance of the agroecosystem. On the widespread sandy kaolinitic soils in sub-Sahara Africa, numerous published results have shows that without appropiate organic inputs, inorganic fertilizer alone cannot sustain crop yield and maintain soil fertility in the long run because of soil acideification, loss of soil organic matter and compaction. The adoption of management practices that integrate organic, chemical and biological inputs into economically and environmentally sound production systems is an essential step towards sustaining high crop yields and preventing land degradation in the region. In the humid forest region, where root crops and tree crops are ecologically more suitable, agroforestry systems, such as multistory homestead gardens, plantation/crop combinations, and alley cropping, appear to have a high potencial for maintaining soil organic matter at levels adequate for sustaining crop growth. In the subhumid and humid/subhumid transition zones, crop residue mulch, minimum tillage and leguminous cover crops are promising tecnologies for improving nutrient and water use efficiency and sustaining high yields of maize, sorghum and cowpea. In the semiarid regions, however, improvement of millet and sorghum yields is severely limited by the lack of organic inputs. The potencial for increasing and sustaining food crop production in the seminarid zone ultimately depends upon successful integration of crop, fodder and fuelwood production within a farming community.

This book contains 23 peer-reviewed papers presented during the 'International Symposium on Balanced Nutrient Management Systems' which was held between 9 and 12 October 2000 in Cotonou, Republic of Benin. This book is presented in seven sections (i) general introduction; (ii) variability on physical and socioeconomic factors and its consequences for selection of representative areas for integrated nutrient management (INM) research; (iii) soil processes determining nutrient dynamics, particularly N and P; (iv) interactions between organic and mineral nutrient sources; (v) improved utilization of rock phosphate; (vi) decision support systems to improve resource use at farm level: on-farm testing of improved technologies; and (vii) recommendations. The currently accepted INM approach advocates the use of organic resources and mineral fertilizer inputs to redress nutrient depletion and sustain crop production. It also ensures that development of nutrient management strategies is problem-driven and involves farmers that are the end-users of such technologies.

World Bank Technical Paper No. 408. This report is a critical review of the technical, economic, and institutional constraints on improving soil fertility in Sub-Saharan Africa, and the actions recommended to address them. Action plans prepared for Ghana, Kenya, Malawi, and Mali examine the demand for and supply of mineral fertilizers, the exploitation of local mineral resources, the prevention of soil erosion and increasing soil-water retention, and soil fertility management using organic technologies and management practices.

This publication reviews issues related to land degradation, with focus on problems of soil fertility management in sub-Saharan Africa. It highlights some successful experiences in the region, constraints and possible solutions specific to the major agro-ecological zones and the importance of the holistic and participatory approaches for soil productivity improvement. The need for action and collaborative efforts of all stakeholders, within the framework of ongoing initiatives, are emphasized. It is hoped that this document will contribute to increase awareness of senior specialists and policy-makers about the problems and alternative solutions towards enhanced and sustained soil productivity.

Legumes play an important role in the cropping systems of sub Saharan Africa (SSA). Legumes are an important source of nutrition to both humans and livestock by providing the much needed protein, minerals, fibre and vitamins. The sale of legumes seed, leaves and fibre generates income for the marginalized communities especially women. Cultivation of legumes is essential for the regeneration of nutrient-deficient soils. By biologically fixing nitrogen (BNF) in the soil, legumes provide a relatively low-cost method of replacing otherwise expensive inorganic nitrogen in the soil. This enhances soil fertility and boosts subsequent cereal crop yields. Production of legumes in SSA is however; hampered by a number of constraints among them low and declining soil fertility, low soil pH, high salinity, drought and flooding, poor access to improved germplasm, diseases, pests and weeds. Farmers need to learn how to overcome these constraints if the full benefits of legumes are to be gained. This book presents a synthesis of research work on legumes and draws attention to the importance of legumes in integrated soil fertility management (ISFM) and poverty alleviation in SSA.

History and evolution. Resource and crop management. Crop improvement. Plant health management. Looking ahead.

Judicious soil fertility management is crucial for sustainable crop production and food security in sub-Saharan Africa (SSA). This book describes the various concepts and approaches underlying soil and soil fertility management research in SSA over the last fifty years. It provides examples of important innovations generated and assesses the position of research within the research-to-development continuum, including how innovations have been validated with the intended beneficiaries. Using the experience of the International Institute of Tropical Agriculture (IITA) as a case study, the authors analyse how processes, partnerships and other factors have affected research priorities, the delivery of outputs, and their uptake by farming communities in SSA. They evaluate both successes and failures of past investments in soil fertility research and important lessons learnt which provide crucial information for national and international scientists currently engaged in this research area. The book is organised in a number of chapters each covering a chronological period characterised by its primary research content and approaches and by the dominant research paradigms and delivery models.