Assessment of maturity indices of rock phosphate enriched composts using variable crop residues

•Assessed maturity indices of rock phosphate enriched composts with variable C/N.•Distinct variations in NH4+-N, NO3−-N, Olsen-P and NH4OAc-K were found in composts.•Enriched compost prepared with rice straw found well-matured and stabilized compost.•Enriched composts could be used to supplement costly fertilizer for crop production. This study aimed to asses maturity indices of rock phosphate enriched composts using crop residues having variable C/N ratios. There were distinct differences in concentration of NH4+-N, NO3−-N, Olsen-P and NH4OAc-K for composts generated from different crop residues, the highest being in rice straw. Water soluble P varied from 3.47–4.45% of total P, while citrate soluble P varied from 32.7–54.0% of total P. Rice straw composts showed lower C/N, WSC/Org-N and E4/E6 ratio and higher germination index indicating that they are well-matured and stabilized compost. The relative order of performance of crop residues in aggrading compost quality was chickpea stover>rice straw>mustard stover>wheat straw>tree leaves. The results demonstrated that all the enriched composts had higher contents of available nutrients and quality indices, indicating that enriched composts could be used to substitute costly chemical fertilizers for crop production.