Impact of Organic Amendments on Soil Organic Carbon Dynamics: A Kinetic Modelling Approach

Abstract

This study investigates the dynamics of carbon (C) mineralization and carbon dioxide (CO2) emissions in tropical soil treated with different organic amendments over a 120-day incubation period. The findings reveal a notable spike in CO2 emissions during the initial three days, primarily due to the quick breakdown of easily degradable organic materials. Following this peak, emissions decreased significantly until day 24, stabilizing afterward. Among the organic amendments, cow dung manure produced the highest CO2 emissions (129.13 mg C kg⁻¹), and maize straw yielded the lowest (98.74 mg C kg⁻¹). A combination of cow dung and rice straw resulted in substantial CO2 production (122.66 mg C kg⁻¹). When cumulative C mineralization was modeled using first-order and second-order kinetic equations, cow dung manure showed the highest mineralization rates and maize straw the lowest due to its high lignin content. The first-order model effectively characterized long-term C mineralization dynamics, showing the strong R² values between 0.9198 and 0.9864. This study highlights a crucial paradox in soil management: while organic amendments like cow dung enhance short-term nutrient availability. Conversely, amendments like maize straw, despite their lower mineralization rates, foster the formation of stable C pools essential for sustainable soil health, emphasizing the importance of choosing organic amendments based on their long-term objectives for C management and climate change mitigation.