标题：THE EFFECTS OF IRRIGATION REGIMES ON NITROGEN AND PHOSPHORUS LEACHING LOSSES OF PERCOLATION WATER ON PADDY RICE FIELDS IN THE LOWER REACHES OF THE YANGTZE RIVER
摘要：Many water-saving techniques have been adopted to improve rice cultivation methods in China, but further investigation is needed to explore the environmental impact of these technologies. The aim of this study was to investigate the effects of nitrogen (N) and phosphorus (P) leaching losses under simulating soil conditions in a real environment under different water managements. Determination index of nitrogen included Ammonium nitrogen (NH_4~+-N), Nitrate nitrogen (NO_3~--N), Total nitrogen (TN) and for P was Total phosphorus (TP). Three water treatments, i.e. flooding irrigation (FI), shallow adjusting irrigation (SAI), and controlled irrigation (CI), were conducted in the lower reaches of the Yangtze River. Results showed that NH_4~+-N was the major form of N in percolation water, which accounted for 47.7-51.5% of the total nitrogen leaching losses under different water managements. Mean TN and NH_4~+-N concentrations were significantly higher in CI and SAI than in FI during the most of the rice growth stage, presenting a trend of SAI>CI>FI. The considerably high TN and NH_4~+-N concentrations via leaching can cause eutrophication of water bodies in the nearby region of paddy fields during the rice growing season. However, the NO_3~--N concentrations during the most rice growth stage showed a trend of CI>SAI>FI. The TP concentrations for all treatments kept below 0.2 mg L~(-1), indicating a small risk of P leaching losses. As a result, it is necessary to comprehensively consider the negative impact on environmental pollution while considering the water-saving benefits of water-saving irrigation. According to the experimental data of this study, CI is more suitable for application in the lower reaches of the Yangtze River of southern China than SAI.
