Cover Crop Residue Amount and Quality Effects on Soil Organic Carbon Mineralization

Decline in soil organic carbon (SOC) and the associated impacts on crop production under conventional farming raises concerns on how alternative management practices increase SOC sequestration and improve agricultural sustainability. This study aimed to understand SOC mineralization kinetics with different cover crop (CC) residue amendments. Soil samples were collected from a fallow and three CC (pea, oat, and canola) plots. Soil samples from the CC plots were manipulated with zero, five, and 10 Mg ha(-1) of the respective CC residues. All soil samples were incubated for eight weeks, SOC mineralization was monitored, and the first order kinetic and parabolic equation models were fitted to the observed data for estimating labile SOC (C-0), and the decomposition rate constant (k). Subsequent comparisons of fitted model parameters were based on the first order kinetic model. The C-0 varied with the residue amount while k varied with CC type. C-0 was 591-858% greater with 10 Mg ha(-1) and 289-456% greater with five Mg ha(-1) residue additions while k was 122-297% greater with 10 Mg ha(-1) and 94-240% greater with five Mg ha(-1) residue additions when compared to the fallow treatment. The CC residue stimulated cumulative carbon mineralization (C-min) irrespective of CC type, suggesting that cover cropping has potential to improve SOC cycling in agroecosystems.