Transformation of Organic Matter in Soil in Relation to Mineralisation of Carbon and Nutrient Availability

Three organic matters, viz., F.Y.M. (Farmyard manure), dhaincha (Sesbania), and poddy straw were incorporated in soil and incubated for 120 days to study the rate of their decomposition, pattern of nutrient mineralisation and their efficiency as soil organic matter builder.

The rate of CO₂ evolution from all the treatments was found to be highest within the first 48 hours of incubation. Farmyard manure has been graded as the best material amongst the three as soil organic matter builder, followed by dhaincha, straw being least efficient in this respect. As supplier of N, P and K to the immediate next crop, the efficiencies of the organic materials have been graded as follows: for N, dhaincha > F. Y.M. > straw; for P, F. Y.M. > dhaincha > straw; and for K, straw > dhaincha > F.Y.M. Straw maintained nitrate depression throughout the period of incubation. After 120 days of incubation, both straw and F.Y.M. maintained higher soil pH than control, whereas soil with dhaincha maintained the same pH as that of control.