Phosphorus Supplying Capacity of Value Added Compost Prepared from Low-Grade Indian Rock Phosphates and Crop Residue

Abstract

In this study, value added compost was prepared from low-grade Indian rock phosphates (RPs) and isabgol straw as an alternative sources of phosphorus. Three different sources of low-grade RP namely Udaipur, Jhabua and Purulia were evaluated for alternative source of P. Total carbon (C) decreased while total nitrogen (N) increased, leading to a decrease in the C/N ratio at the end of composting. Notable increases in total and available P was found in the composts charged with RPs. The rate of P released from the composts was studied through leaching experiment in the laboratory. An incubation study was carried out to evaluate the effect of different compost on soil P availability. Data revealed that the sharp increase in water soluble P from all the compost at 14 days of leaching then a gradual decrease. Significantly higher water soluble P released from the value added (RP charged) compost as compared to ordinary compost throughout the leaching period. Application of value added compost in soil increased water soluble, available P, microbial biomass C and P as well as acid and alkaline phosphatase activity in soil. Initially, the value added compost showed lower available P as compared to DAP however, improved significantly at a later stage of incubation. The increase in different labile pools of P in soil amended with value added compost also indicates substantial amount of P mobilized from the compost during incubation. Thus, the value added compost could be an effective alternative of chemical fertilizer and promising technology to utilize low-grade RP as P source.