Increasing Effective Use of Straw-Derived Nitrogen by Alternate Wetting/Drying Irrigation Combined with N Fertilization Addition in a Soil–Rice System

Abstract

Straw-derived N (Straw-N) is an important organic N source, but its distribution in soil–rice systems regulated by water management and N fertilization is poorly understood. Therefore, a pot experiment using 15N-labeled wheat residue was conducted with conventional flooded irrigation (CF) and alternate wetting/drying irrigation (AWD) both with and without N fertilization. Results showed that the whole-plant straw–N recovery rate and the soil residue rate were 9.2–11.9% and 33.5–43.1%, and 10.2–13.8% and 33.7–70.2% at panicle initiation stage (PI) and mature stage (MS), respectively. There was no interaction between water management and N fertilization. Compared to CF, AWD did not affect whole-plant straw-N absorption and significantly changed its distribution in various plant parts, such as increasing the straw-N accumulation in roots at PI and decreasing it at MS. N fertilization addition markedly promoted the transfer of straw-N to the plant but reduced the contribution rate of N uptake by the plant. Furthermore, AWD or N fertilization addition allowed more straw-N to remain in the soil, and a positive interaction effect on the straw-N loss mitigation was found. These results suggest that AWD combined with N fertilization addition is a great measure to improve the efficient utilization of straw-N and avoid the risk of environmental pollution in a soil–rice system.