Excessive chemical nitrogen (N) fertilizer application and flood irrigation in rice production can lead to substantial soil-N losses and low nitrogen-use-efficiency (NUE) in rice due to N leaching from red paddy soils. Although inoculation of irrigated fields with nitrogen-fixing cyanobacteria (NFC) has been shown to increase rice yield, there are few studies on N leaching and NUE in response to NFC when used in place of urea. A two-year field experiment was carried out to examine the concentrations of ammonium-N (NH₄⁺-N), nitrate-N (NO₃⁻-N), total dissolved N (TDN) and dissolved organic N (DON) in percolated irrigation water, as well as cumulative leaching losses after NFC was used to replace different application rates of urea in double cropped rice grown in red paddy soil. Four treatments were established: 1) CK, the control with no application of urea or NFC; 2) N10C0, a conventional full application of urea only; 3) N5C5, addition of a half-application of NFC to replace half of the conventional application rate of urea (N5C5); and 4) N0C10, a full application of NFC only. In 2017 and 2018, although the average rice yield of N0C10 was 25.0 % higher than that of CK, it was 23.8 % lower than that of N10C0. The average NUE of N10C0 was 34.7 %, and the average TDN leaching loss was 13.9 kg ha^-1 per crop each year. Correspondingly, NUE of N5C5 was 47.7 %, which was 37.5 % higher than that of N10C0. Replacing 50 % of urea with NFC did not significantly decrease rice yield, but it reduced TDN leaching by 37.2 %. The results showed that the conventional way of fertilization caused the most N loss, while replacing partial urea with NFC significantly reduced the leaching losses of NH₄⁺-N, NO₃⁻-N and DON. Moreover, replacing 50 % of urea with NFC can retain more soil N than conventional fertilization at the end of the rice season because NFC can intercept, fix and delay release of N. Thus, the multiple functions of NFC in N cycling dynamics are more conducive to the retention of N by soil and greatly reduces N leaching.

水稻生产中过量施用化学氮肥和洪水灌溉会导致水稻红壤中氮素的淋失，从而导致土壤氮素的大量流失和氮素利用效率（NUE）的降低。尽管已经显示了用固氮蓝细菌（NGC）灌溉灌溉田地可提高水稻产量，但很少有人研究氮肥替代尿素时对氮的淋失和NUE的响应。为期两年的田间试验中进行检验的铵态氮（NH浓度₄ ⁺ -N），硝酸-N（NO ₃ ^--N），渗滤灌溉水中的总溶解氮（TDN）和溶解有机氮（DON），以及使用NFC代替红壤稻田双季稻中尿素的不同施用量后累积的淋失损失。建立了四个处理方法：1）CK，不使用尿素或NFC的对照；2）N10C0，仅常规尿素的全部应用；3）N5C5，添加一半的NFC，以取代常规尿素（N5C5）的一半使用；4）N0C10，仅适用于NFC。在2017年和2018年，尽管N0C10的平均水稻产量比CK高25.0％，但比N10C0的平均水稻低23.8％。N10C0的平均NUE为34.7％，平均TDN浸出损失为13.9 kg ha ^-1每庄稼每年。相应地，N5C5的NUE为47.7％，比N10C0的NUE高37.5％。用NFC代替50％的尿素不会显着降低水稻的产量，但可减少37.2％的TDN浸出。结果表明，常规施肥方式造成的氮素损失最多，而用NFC代替部分尿素可显着减少NH ₄ ⁺ -N，NO ₃ ^-- N和DON的淋失。此外，在水稻季节结束时，用NFC代替50％的尿素比常规施肥可保留更多的土壤N，因为NFC可以截留，固定和延迟N的释放。因此，NFC在N循环动力学中的多重功能更加有利。可以保留土壤中的氮，并大大减少氮的淋失。