Temporal change in N₂O emission derived from cabbage and lettuce residues

Abstract

Crop residue is an important source of N₂O emission from agricultural fields, although it is a less-studied N₂O source compared with fertilizer application. The aims of this study were to investigate the temporal change in N₂O emission from cabbage and lettuce residues and to elucidate the relationship between N₂O emission derived from crop residue and WFPS (water-filled pore space). Cabbage and lettuce crop residue were placed onto the surface of repacked soil cores with a soil moisture content of 55％ or 70％ WFPS. N₂O flux was measured for 64 days. Approximately 50％ of the cumulative N₂O emission was emitted for over 20–27 days after lettuce residue application, whereas it was emitted for over 38–45 days after the cabbage residue application. These results may be attributed to the difference in decomposition rates between the crop residues. Moreover, our results suggested that WFPS affected N₂O emission after crop residue input through change in contributions of nitrification and denitrification to N₂O production. Crop residue type and soil water content were the major factors affecting N₂O emission after the crop residue input in agricultural fields.