Impact of long-term manuring and cropping system on stability of humus associated with clay-organic complex

The objective was to study the impact of ten year's manuring and fertilization on chemical stability of clay-organic complex (COC) in rice-potato-wheat (R-P-W) and maize-potato-onion (M-P-O) cropping systems. Soil samples were collected from the control, 100% NPK-Fertilizer, 100% N-Vermicompost (VC), 50% NPK-Fertilizer + 50% N-VC, 100% NPK-Fertilizer + crop residue (CR), 100% N-VC + CR. The stability (1/k) of humus C i.e. inverse of humus desorption rate constant (k) in hours (h), in COC was higher in 100% N-VC an1d 00% N-VC + CR in both the cropping systems. The C:N ratio of humic acid (HA) was also higher in the treatments receiving full organics (100% N-VC and 100% N-VC + CR) and showed positive correlation (p < 0.05) with the humus C stability in COC. Long-term manuring treatments created C = N and C-O stretching of aromatic ether in HA extracted from 100% NPK-VC and other selected treatments in both the cropping systems. 100% N-VC and 100%N-VC + CR produced higher stability of humus-C in Inceptisol. The R-P-W imparted higher stability of humus C than M-P-O cropping system.