控制排水条件下淹水稻田田面及地下水氮浓度变化

Changes of nitrogen concentration for surface and groundwater in flooding paddy field under controlled drainage

为了在减少农田面源污染,提高氮肥的利用效率。该文通过蒸渗测坑进行淹水稻田不同渗漏强度控制试验,研究了稻田施肥后NH4+-N、NO3--N浓度变化及各生育阶段不同渗漏强度稻田水NH4+-N、NO3--N浓度变化。结果表明:施分蘖肥后,地表水及地下水NH4+-N浓度急剧升高而后回落,均在施肥后第5天出现峰值,分别为17.75和10.34mg/L;地表水NO3--N浓度短暂升高后便回落,在施肥后第2天出现峰值,但地下水NO3--N浓度急剧上升而后回落,在施肥后第5天出现峰值(3.25mg/L),6d上升了249.4%。稻田补水会扰动土壤,促进土壤表层吸附的NH4+-N的释放及硝化进程,使地表水中NH4+-N和NO3--N浓度升高,随着淹水时间的延长,NH4+-N和NO3--N浓度会随之降低。不同渗漏强度(2和4mm/d)对稻田水氮素变化有一定影响,但各处理之间差异不显著。因此,施肥后应该避免排水,应避免雨后和灌水后立即进行地表排水。

To reduce agricultural non-point source pollution and improve nitrogen use efficiency,the research on the changes of concentrations of NH4＋-N and NO3--N in surface and ground water after fertilizer application and changes of that at each growth stage was conducted based on experimental test in flooding paddy field under different leakage rates by use of lysimeter.Results showed that after fertilizer application,the concentrations of NH4＋-N in both surface and ground water increased significantly and then decreased,and their peak values both appeared at the 5th day after fertilizer application,they were 17.75 and 10.34mg/L,respectively in surface water and ground water.Results also showed that the concentration of NO3--N in surface water decreased after a brief increment,and its peak value appeared at the 2nd day after fertilizer application.While the concentration of NO3--N in ground water gradually rose and then decreased,its peak value appeared at the 5th day after fertilizer application（3.25mg/L）.Compared with the value at the 1st day,the concentrations of NO3--N in ground water increased to 249.4% at 6th day.Water was supplied in the paddy and soil in paddy was disturbed and the process that absorption of NH4＋-N in the surface soil and nitrification process were promoted.Then the concentrations of NH4＋-N and NO3--N in surface water was increased and concentrations of that gradually decreased with the flooding time increasing.Different leakage（2 and 4mm/d） had a certain influence on the changes of nitrogen,but the difference between each treatment was not significant.Therefore,drainage should be avoided after fertilizing,immediate drainage should be avoided after rain and surface irrigation.