Residual Effect of Rock Phosphate and Waste Mica Enriched Compost on Yield and Nutrient Uptake by Soybean

A field experiment was conducted to evaluate the residual effect of rock phosphate and waste mica enriched compost on phosphorus and potassium supplying capacity under soybean crop grown after wheat in a Typic Haplustept. Enriched compost prepared using rice straw, rock phosphate, waste mica and Aspergillus awamori had higher chemical (total P, K, Ca, Mg and micronutrients) as well as biological properties (microbial biomass C, dehydrogenase, phosphatase activity and microbial biomass P) than ordinary compost. Application of enriched compost @ 5 t ha-1 along with 50% recommended dose of fertilizer (RDF) to the first crop resulted in a significant increase in soybean grain and stover yield (1.52 and 4.33 t ha-1 respectively) grown on residual fertility. Significant increase in N, P and K uptake by soybean grown on residual fertility after wheat were observed over control. Application of fertilizer materials to the first crop also resulted in significantly higher P recoveries in soybean crop. However, higher K recoveries were obtained in the treatment receiving integrated use of ordinary compost applied at lower dose along with chemical fertilizers i.e. 50% RDF. The results clearly demonstrated that enriched compost could be used for supplying phosphorus and potassium to crop grown in a cropping sequence which could maintain soil fertility and substitute half of the water soluble fertilizers demand by the residual crop.