Soil Fertility Dynamics of Ultisol as influenced by greengram and mucuna green manures

Synchronisation between supply of plant available nutrients to crops’ needs and uptake is a major challenge in Sub- Saharan Africa. Experiments were set to evaluate release patterns and availability of nutrients by leguminous green manures in soil. Mucuna and greengram materials were buried 10 cm in mesh bags.

Replicated bags removed weekly and analysed to determine decomposition rates and quantities of nutrients released into soil. Mucuna decomposition was faster compared to greengram, from third to twelve weeks of incubation. This implies that greengram has relatively more resistant materials to decomposition compared to mucuna.

Maximum effect on soil nutrient content occurred in sixth and seventh weeks after application of green manures. Total organic C in soils increased by a factor of 2.3 to 3.2. Total N increased significantly from 1.28% to 2.64% at sixth week in soil with greengram and 2.83% at seventh week in soil with mucuna.

Available P content of soil increased from 0.03 to 0.39 and 0.37 mg kg-1 in soil treated with greengram and mucuna. Optimum microbial population was attained from fifth to seventh week after manure application, with 2.3 × 108 in soil with greengram and 3.08 × 108 with mucuna, significantly improved compared to original population.