Friday, 14 July 2006 - 2:25 PM

Developing Management Strategies to Sustain Soil Fertility in West Africa.

Mateugue Diack, Université Gaston Berger, Saint- Louis, Senegal

Food security is one of the most serious challenges facing the countries of West African sub-region. The rapid population growth which, in the past decade, exceeded growth in agricultural production, has resulted in pressure on land and cultivation on marginal lands to maintain food production at minimum level. Coupled with this situation, is the increased population of livestock on the rangelands which are hardly managed and, in most cases, over-stocked, causing serious soil erosion and land degradation. Deforestation, land mismanagement, bush fires and inappropriate soil management and farming practices among others have accentuated land as well as environment degradation. Nutrient depletion is the most important element in the land degradation equation. Unlike the more rather abrupt catastrophes such as drought and earthquakes, the reduction of the fertility on the soil is a gradual but steady process. For nations whose livelihood is solely dependent on agricultural production, unchecked soil fertility declines poses a major threat to economic development. In the fight against land degradation, emphasis needs to be shifted away from the erection of physical structures to a better understanding of the role of vegetation as a provider of organic matter for soil improvement and canopy to intercept rainfall. Many areas in West Africa have predominant inherently low fertility soils; degraded soils-soils cropped over long periods and removing nutrients through crops and residues both domestic and export crops-without replenishing the nutrient lost and, marginal areas unsuitable for agricultural activities. In addition, non-adoption of improved management practices by the majority of farmers has resulted in accelerated erosion, one of the major causes of land degradation. Removal of vegetative cover and plants residues for alternative uses has contributed little to erosion control in these environments. One of the serious threats to the environment is the annual bush fires that occur at the end of the rainy season and which is deliberate in many cases but also in few accidental. The bush fires destroy the organic matter in the top soil in particular in the semi-arid zones where the accumulated organic matter is crucial to soil fertility maintenance. A few studies have shown that management practices using the quality of agroforestry tree or shrub litter could affect the diversity of microbial biomass. These findings showed that manipulating residues to promote microbial biomass might be a way to improve soil sealing index for which microorganisms are known to play a role in forming aggregates. Plant residue mixes, added together or in temporal sequence, offer potentials to meet crop nutrient needs while improving soil quality and manipulating the microbial community to promote crop yields. However, to reach these goals, a much greater coordinated research effort is needed in all regions of West Africa to: 1) characterize soil microbial communities and microbial mediated processes; 2) evaluate the benefits to society from policy changes regarding soil quality and soil productivity and 3) set agricultural and environmental policies for decision makers. Key words: management practices, soil fertility, soil quality, agricultural and environmental policy.

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