Author(s): Bin Lu; Shiqiang Wu; Shuang’En Yu; Yanyan Wang
Keywords: Controlled drainage; Paddy water; NH3-N; NO3 --N; Pollution reducing and water saving
Abstract: In the serious situation of agriculture non-point pollution problem, controlled drainage is applied to agricultural water management as an important and efficient approach. To simulate the process of paddy field waterlogged after once intensive rainfall in different periods, we designed series of tests at four major growth stages of rice. Those tests maintained paddy waterlogged at 10 days with certain water depth and different leakage intensity. This article showed dynamic changes of ammonia nitrogen (NH3-N) and nitrate nitrogen (NO3 --N) concentration in surface and subsurface paddy water, analyzed the effect from leakage intensity to N leaching, calculated loads of N losses through surface drainage, and demonstrated the effect of pollution reducing and water saving form paddy field controlled drainage. The results indicated that: general speaking, the concentration of NH3-N and NO3 --N in paddy water was declined with the prolonging of waterlogged duration. Amount of N leaching under 4mm/d leakage intensity, was about two times larger than the treatments of 2mm/d. Results of ANOVA for N concentration through leaching under two leakage intensity, showed the difference between them was not significant. So, the main reason to effect N leaching amount is seepage water volume. Loads of N losses in surface paddy water were declined with the prolonging of waterlogged duration. Compared with tradition drainage, controlled drainage reduced N loss in surface water by 95. 6% , 78. 7% , 59. 6% and 87. 4% at four stages respectively. Surface water has higher N concentration at the 1st day after paddy field waterlogged at each stage, and loads of N losses in surface water was increased at the 4th day after paddy field waterlogged at jointing-booting and milking stage. Therefore, surface drainage should be avoided in those two conditions.