Effect of selected soil characteristics on net nitrogen mineralized from crimson clover residues

Abstract

Crimson clover ( Trifolium incarnatum L.) is a leguminous cover crop that can supply nitrogen (N) to the subsequent cash crop through N mineralization. The amount of N mineralized from crimson clover residue depends in part on residue quality and environmental conditions, but limited information is available on the effect of soil characteristics. We used subsets of 17 soils from across the United States to conduct four growth chamber/incubator studies to evaluate how selected soil characteristics affect net N mineralized or N released from crimson clover residue. Two studies used litter bags with whole clover residue placed on the soil surface: one under diurnal cycles of air temperature and relative humidity, and one under constant temperature. Two other studies used ground clover residue at constant temperature: one with residue on the soil surface, and one with incorporated residue. Results with surface‐applied residue showed no differences among soils in N release and/or net N mineralized from the residue. Nitrogen release from surface residue was slightly associated with soil pH ( r ²  = 0.36) or silt content ( r ²  = 0.20), and net N mineralized from the residue was not related to soil characteristics or showed only a slight relationship to the amount of N mineralized from soil organic matter ( r ²  = 0.33). In contrast, soils with incorporated residue showed differences among soils in net N mineralized that were strongly associated with pH, potentially mineralizable N, and silt content ( r ²  = 0.87). These results suggest that the soil characteristics evaluated had a stronger effect on the net N mineralization from incorporated clover residue than on the net N mineralization or N release from surface residue.