直播水稻田田面水氮素动态变化及径流损失研究

Research on the Dynamic Change and Runoff Loss of Nitrogen in the Soil Surface Water of Rice Fields of Direct Seeding Cultivation

[目的]为直播水稻田的合理施用氮肥和灌水及防止氮素污染地表水提供科学依据。[方法]通过田间试验，对太湖流域丹阳地区直播水稻田田面水氮素动态变化特征及径流损失进行研究。[结果1施肥使田面水氮素浓度迅速提高，施氮后第1天田面水TN和NH4^＋-N的浓度达峰值43．99和23．31mg／L，第7天分别下降至峰值的23．50％～30．02％和16．22％～23．84％；田面水的NO3^- -N浓度在施氮后第3天达最大值7．51mg／L．随后逐渐下降。施氮后3～5d内，田面水NH4^＋-N／TN比值达动态观察期中的最大值0．50～0．69，此后逐渐降低。田面水NO3^- -N／TN比值也先升后降，均在0．31以下。丹阳当季直播稻田TN地表径流损失量为23．84kg／hm^2，占施氮量的5．05％；NH4^＋-N流失量为13．24kg／hm^2，占施氮量的2．88％。烤田排水TN径流损失为13．49kg／hm^2，占总施氮量的2．93％。[结论]NH4^＋-N是稻田田面水氮素的主要形态，施氮后7d是防止稻田氮素流失的关键时期，

[ Objective] The purpose was to provide scientific basis for fertilizing nitrogen （N） fertilizer reasonably in the rice fields of direct seeding cultivation and protecting surface water from N pollution. [ Method] The dynamic change characters and runoff loss of N in the soil surface water of rlce fields of direct seeding cultivation in Danyang area of Tai Lake basin were researched through field experiment. [ Result] Fertilization rapidly enhanced the conch, of N in soil surface water. On the 1 st day since fertilizing N, the conch, of TN and NH4^＋ -N in soil surface water reached their peak values of 43.99 and 23.31 mg/L. On the 7th day, they decreased to 23.50% - 30.02% and 16.22% - 23.84% of their peak values resp. On the 3rd day since fertilizing N, the cohen, of NO3^- -N in soil surface water reached its maximum of 7.51 mg/L and then decreased gradually. In 3 - 5 d since fertilizing N, the NH4^＋ -N/TN ratio of soil surface water reached the maximum of its dynamic observation period, which was 0.50 - 0.69 and then deereased gradually. The NO^3- -N/TN ratio of soil surface water also first increased and then decreased, which was always below 0.31. The surface runoff loss amount of TN was 23.84 kg/hm^2 in the rice fields of seasonal direct seeding cultivation of Danyang, which accounted for 5.05% in N application rate. The loss amount of NH4^＋-N was 13.24 kg/hm^2 , which accounted for 2.88% in N application rate. The runoff loss of TN through drainage in baking period was 13.49 kg/hm^2 , which accounted for 2.93% in total N application rate. [ Conclusion] NH4^＋ -N was the main form of N in soil surface water of riee fields and the 7 days since fertilizing N was the key period for preventing N in rice fields from loss.