Carbon and nitrogen mineralization patterns of two contrasting crop residues in a Mollisol: Effects of residue type and placement in soils

Predicting carbon (C) mineralization of crop residues returned to soils is important for forecasting carbon dioxide (CO2) emissions into the atmosphere and soil nitrogen (N) availability. In this study, a laboratory incubation experiment was conducted to investigate C mineralization of residues of soybean (Glycine max), maize (Zea mays), and their mixture placed on the soil surface and incorporated into the soils in a Mollisol in northeast China. Both the residue type and placement significantly affected C and N mineralization, while no significant interactions between them were observed on cumulative C mineralization. The soybean residue had a higher decomposition rate than the maize residue regardless of their placements; decomposition rates for both soybean and maize residues placed on the soil surface were higher than those of the same residues incorporated into the soils. Moreover, non-additive effects on the contribution of each residue type to C mineralization of the residue mixture were not observed. Our results suggest that crop residue with a low N concentration and a high C/N ratio (such as maize) can be incorporated into soils to immobilize N and decrease CO2 emissions in comparison with crop residue placed on the soil surface.

► Both residue type and placement significantly affected C and N mineralization.
► No significant interaction between residue type and placement was observed on C mineralization.
► Soybean had a higher residue decomposition rate than maize regardless of their placements.
► Residue decomposition rate was higher on soil surface than that incorporated into the soils.
► There was an additive effect on contribution of each residue to C mineralization of residue mixture.