Abstract
To cope with challenges of food security and water scarcity in rice production, water-saving ground cover rice production systems (GCRPSs) are increasingly adopted in China and globally. Reduced soil moisture as well as increased soil aeration and temperature under GCRPSs may promote soil N transformations, and in turn give rise to environmental challenges. These include emissions of the potent greenhouse gas nitrous oxide (N2O) and atmospheric pollutant nitric oxide (NO). Using conventional flooding rice cultivation as a reference, a three-year field experiment was conducted to investigate the performances of GCRPSs under inorganic (urea) or integrated nutrient management (a combination of synthetic and organic fertilizers), with regards to soil N2O and NO emissions as well as grain yields. N2O and NO emissions in GCRPSs exhibited high seasonal and interannual variations along with changes in soil inorganic N content and rainfall. When urea alone was applied, the average N2O and NO emissions from GCRPSs were 4.11 and 0.14 kg N ha−1, respectively. These emissions were significantly higher than those of conventional rice cultivation, with 1.47 and 0.052 kg N ha−1 for N2O and NO, respectively. When integrated nutrient management was performed for GCRPSs, N2O and NO emissions were reduced by approximately 77% and 50%, respectively, i.e., the emission magnitude comparable with N-trace gas losses from conventional rice cultivation. Moreover, GCRPSs with integrated nutrient management resulted in optimal grain yields, and thus, the yield-scaled N2O + NO emissions were the lowest compared to other treatments. Averaged over 3 years, the direct emission factors of N2O and NO for GCRPSs with urea alone were 2.58% and 0.064%, respectively. Those for GCRPSs with integrated nutrient management were 0.48% and 0.016%, respectively. The results of this study suggest that GCRPS with integrated nutrient management is an eco-friendly strategy for optimizing crop yields while mitigating N2O and NO emissions.
Published Version
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