Kinetics of Soil Carbon Mineralization Under Continuous Site-Specific Nutrient Management in Ultisols Under Cassava

Abstract

ABSTRACT The present study focused on the effect of 10 years of continuous fertilizer trials on soil organic carbon (SOC) mineralization in cassava grown ultisols. The study determines the carbon (C) mineralization potential, dynamics, and kinetics of C mineralization by fitting five decay models, significance of various long-term fertilizer applications on C mineralization and the relationship between soil physico-chemical properties with carbon mineralization parameters derived from the best model. To determine the potential of the soil to mineralize organic C a short-term aerobic incubation procedure – alkali trap method – was used. The best model fitting first-order E (R2 = 0.994) was used to describe the dynamics and kinetics of C mineralization. Relationships between soil physico-chemical properties and C mineralization parameters of first-order E model were studied by using correlation analysis. The site-specific nutrient management (SSNM) treatment showed the highest carbon dioxide-carbon (CO2-C) evolution value (2049.61 mg of CO2-C kg−1 soil) while NPK omission treatment showed the lowest (1703.37 mg of CO2-C kg−1 soil). The initial potential rate of carbon mineralization (C0k) was highest for SSNM treatment (159.78 mg kg−1) and lowest for K omission treatment (123.25 mg kg−1) indicating that the organic matter quality has increased in continuous SSNM treatment for 10 years compared to all other treatments. Significant positive correlations were shown between cumulative C evolved (Cm) and SOC. Significant negative correlations were observed between size of the mineralization flush (C1) and silt as well as between potentially mineralizable carbon (C0K) and clay.