Soil Organic Matter and Soil Water Interactivity in the Semi-Arid Tropics of West Africa.

Soil organic matter (SOM) has many functions in physical, chemical and biological processes in tropical soils. Deforestation has resulted in much SOM decline in the humid tropics. Crop residue removal for various uses and rapid decomposition of organic materials under continuous cultivation contribute to low SOM in the semi-arid and arid tropics. An on-going concern that is expected to worsen with climate change is the occurrence of soil water deficits. Maintenance or improvement of SOM is important to soil water availability through good soil aggregation for rapid water infiltration with little runoff and erosion and for available water holding capacity and water retention. IPCC projects this region to become drier with climate change, and this presents a dire need to sustain food production for the ever increasing population. Prospects for soil water conservation include climate-smart strategies such as intercropping with legumes, use of mulches and cover crops, minimum tillage practices and addition of other organic inputs or polymer-based bio-conditioners. These measures have been shown to improve soil organic matter and water retention properties in short and long terms. Integrated management practices that optimize crop productivity and affect physical soil quality such as use of different sources of organic matter, tillage and/or deficit irrigation has been explored and will be presented.