Compost Amendment Rates Modulate Soil Carbon Mineralization, Nutrient Dynamics, and Microbial–Enzymatic Interactions
摘要
This study examined carbon mineralization, microbial and enzyme activity in soils amended with composts over 18-week incubation. Carbon mineralization followed three phases: initial, intermediate, and stabilization, with T6 (poultry manure compost @ 5 t ha− 1) and T4 (cow dung compost @ 5 t ha− 1) exhibiting the highest carbon mineralization rates, reaching 308.6 and 281.7 mg CO2-C kg− 1. Microbial Biomass Carbon (MBC), Microbial Biomass Nitrogen (MBN), Dehydrogenase activity (DHA), and Basal Soil Respiration (BSR) were strongly correlated and T6 recorded the highest MBC (486.6 ± 1.95 mg kg− 1) and MBN (18.8 ± 0.27 mg kg− 1), with highest bacterial and actinomycetes counts (50.24 × 107 CFU/g and 56.67 × 105 CFU/g). Fungal counts were highest in T2 (42.74 × 103 CFU/g). Nutrient analysis revealed that T6 had the highest mineral N (131.5 mg kg− 1), and T4 showed the highest available P (15.9 mg kg− 1) and available K (115.7 mg kg− 1). The strong positive correlations between MBN, alkaline phosphatase activity, and Cumulative (cm) indicate their interconnectedness in nutrient cycling. Partial Least Squares Regression (PLSR) identified MBC, mineral N, and enzymes as key predictors for Cumulative cm, with MBC having the highest importance score (1.2) followed by mineral N and available K. Among the different treatments, for predicting cumulative cm T6 followed by T4, T10 and T8 were found to best. This study emphasizes the critical role of organic amendments in enhancing microbial activity, sustaining long-term carbon cycling, and improving soil fertility for sustainable soil management.