Phosphorus Delivery Potential in Soil Amended with Rock Phosphate Enriched Composts of Variable Crop Residues under Wheat–Green Gram Cropping Sequence

Abstract

ABSTRACT Understanding phosphorus (P) transformation in soil is necessary to develop sustainable P management practices. An experiment was carried out to evaluate the P fractions and P delivery potential in soil amended with rock phosphate (RP)-enriched composts under the wheat–green gram cropping sequence. The P mineralization study also revealed that the soil treated with RP-enriched composts showed a decline in available P during the initial stages of 30 days but improved significantly with the progress of time. Data emanated from the crop trials showed that significant buildup in available P (AP) was maintained under enriched compost-treated plot than unfertilized control in both the wheat and green gram crops. Total P (TP) increased by 37.4 and 48.9% under rice straw compost (RSC) and RSC+50% NPK-treated plots, respectively, over unfertilized control in wheat. However, the corresponding increases were 32.6 and 36.5% over control for green gram. After wheat, significant improvements in water-soluble P (WSP), microbial biomass P (MBP), and enzyme activities were found in plots receiving enriched composts. Based on information assessed from cluster analysis and principal component analysis, TP, WSP, citrate-soluble P, C/N ratio, and alkaline and acid phosphatase are considered their active role in compost maturity and quality, while TP, MBP, and AP are considered important parameters for P dynamics in soil. Enriched compost prepared using low-grade RP and crop residues could be an alternative and cost-effective option for mitigating the shortage of chemical fertilizers for crop production.