AgroFossilFree - Temperature Sensitivity of Soil Organic Carbon as Affected by Crop Residue and Nutrient Management Options Under Conservation Agriculture

Γενική περιγραφή

Conservation agriculture (CA) helps in soil organic carbon (SOC) restoration and build-up. The aim of the current study was to evaluate the soil aggregation and concentration, mineralization, and thermal stability of aggregate-associated C under CA with different rates of crop residue (CR) retention and nutrient management practices in a 6-year-old experiment situated in the north-western part of Indo-Gangetic Plains (NW-IGP). The treatments were composed of 3 levels of crop residue (CR) retention, i.e., 0 (CR0), 2 (CR2), and 4 (CR4) t ha-1, and six combinations of nitrogen (N) and potassium (K) fertilizer rates in the sub-plots, i.e., 100 and 150 kg N ha-1 and 0, 30, and 60 kg K2O ha-1. Results indicated significant improvement in total SOC, its pools of varying lability, and aggregate-associated C consequent to increment in CR load. Treatment CR4 had ~ 155% and 23.2% higher values of carbon management index (CMI) compared with CR0 and CR2 in 0–5-cm soil depth. Incremental CR load registered accumulation of C-rich macro-aggregates with a subsequent decline in C-poor micro-aggregates. Treatment CR4 recorded the highest values of cumulative C mineralization, but the lowest percentage and decay rate (Kc) of SOC mineralization. The macro-aggregates reported a lower percentage of total SOC mineralized, Kc, and temperature sensitivity (Q10) compared with bulk soil and micro-aggregates. Incremental CR load under ZT promoted physical protection of labile SOC in the form of macro-aggregate-associated C, instead of the recalcitrance of micro-aggregate-associated C. Our results point out towards less temperature sensitivity of physically stabilized SOC under CR4, therefore emphasizing the effectiveness of complete CA practices for sequestration and stabilization of C in the impending global warming scenario.