Alley Cropping in the Moist Savanna of West-Africa III. Soil Organic Matter Fractionation and Soil Productivity

Nitrogen concentration and the size of the particulate organic matter pool were determined as a function of organic inputs and soil characteristics for a range of soils representative of the West-Africa moist savanna zone. In addition, the contributions of the various sources of N to maize uptake were evaluated. The studies, which all involved alley cropping, were conducted in Benin, Togo, and Cote d'Ivoire. Results indicated that sites with larger N inputs in the form of organic residues contained a relatively higher amount of total soil N in the particulate organic matter material. No quantitative relationships between particulate organic matter N contents and individual organic matter inputs were discerned, however. The particulate organic matter N content explained less of the variation in total maize N uptake than the total amount of pruning N added.