稻田中氮素淋失的主要形态是硝态氮而不是铵态氮，为此稻田施用氮肥会对地下水体环境构成潜在的硝态氮污染危险．在双季稻田中，硝态氮淋失呈现典型的二次曲线型季节性消长，早季的淋失高于晚季．在300公斤N／公顷施氮量和540mm排水量条件下，双季稻田中氮素淋失总量可达27公斤N／公顷，其中硝态氮占85％，铵态氮占15％．碳铵的氮素淋失高于尿素．包膜尿素可以有效减少氮肥的淋失． The main form of nitrogen leaching in paddy field is nitrate nitrogen rather than ammonium nitrogen. Therefore, the application of nitrogen fertilizer to paddy fields may pose a potential nitrate nitrogen pollution risk to the groundwater environment. In the double cropping paddy, leaching of nitrate nitrogen showed a typical quadratic curve-type seasonal growth and loss in early season than in late season. Under the condition of 300 kg N / ha and 540 mm displacement, the total amount of nitrogen leaching in double cropping paddy reaches 27 kg N / ha, of which 85% is nitrate and 15% is ammonium. Ammonium bicarbonate leaching is higher than urea. Coated urea can effectively reduce the leaching of nitrogen fertilizer.