Changes in Labile Pools of Soil Organic Carbon in Relation with Crop Productivity in Different Long-term Fertilizer Treatments

Studying the dynamics of soil organic carbon (SOC) is important for understanding the carbon stabilization into different pools. Thus, a 25-year old experiment was used to assess the impact of double rice cropping system with addition of organics and grades of fertilization on labile carbon pools and crop yield sustainability in an Inceptisol in southern India. There was significant decrease (p<0.05) in bulk density with increase in the use of organics over control. Green manure applied (in combination with NPK or NPK+farmyard manure) showed greater mineralisable carbon hence, could say greater microbial activity and carbon turnover. The lowest value of microbial quotient (MQ) in the control indicated a poor quality soil with impairment of its capacity for C cycling. The better nutritional environment to microbial population in the soils under balanced fertilization along with organics increased the quotient. The higher respiration quotient (qCO2) in the control treatment suggested a less efficient use of available carbon by the microbes there.