Effect of Water-Saving Ground Cover Rice Production System on NO Emission from a Rice-Fallow Rotation Cycle

To safeguard food security and water resources, the water-saving ground cover rice-production system (GCRPS) has been increasingly adopted by the agricultural production sector for rice production. However, compared with the conventional paddy rice-production system (CPRPS) with an intermittent irrigation water regime, changes in the soil environment under GCRPS to a larger degree affect the soil biogeochemical processes that regulate the emissions of nitric oxide (NO), an important atmospheric environmental pollution gas. To quantify the differences in NO fluxes between GCRPS and CPRPS and to identify the controlling factors, the NO fluxes were measured in situ in an annual rice-fallow cropping system under different fertilizer treatments on the basis of the static opaque chamber method and chemiluminescence analysis. The results show that during the rice-growing season, high NO emissions were mainly observed during the mid-season drainage period. The seasonal total NO emissions under GCRPS were generally higher than those under CPRPS, with NO direct emission factors of 0.12% and 0.016%, respectively. This difference is mainly due to the higher soil redox potential and temperature under GCRPS. In the fallow season, the NO fluxes in each treatment were negatively correlated with the soil water content. Overall, compared with the CPRPS, the water-saving GCRPS shows potential trends of increased annual NO emission at 0.032% and 0.15%, respectively. To analyze these trends in greater detail, multi-year and multi-site research should be conducted in the future studies.