Changes in N Concentration and Effects of Pollution Reduction in Paddy Field Under Controlled Draina

• 作 者: Bin Lu
• 机 构: Nanjing Hydraulic Research Institute, Nanjing 210029, China
• 出 处: 2015中国农业水土资源保护与自然农法国际论坛
• 发表日期: 2015年11期
• 关键词: controlled drainage paddy water NH4+-N NO3--N pollution reduction

　　Losses of nutrients from paddy field significantly contribute to the eutrophication of lakes in south and east China.In this examination of the agricultural non-point pollution (NPS) problem, paddy field controlled drainage (PFCD) is applied as an important and efficient approach to agricultural water management.To simulate the paddy field waterlogging process after different periods of intensive rainfall, we designed a series of tests at the four major growth stages of rice.These tests kept the paddy waterlogged for 10 days with a specific water depth and different leakage intensities.We observed dynamic changes in ammonia nitrogen (NH4+-N) and nitrate nitrogen (NOa--N) concentration in surface and subsurface paddy water,analyzed the effects of leakage intensity and nitrogen (N) leaching, calculated N losses through drainage, and demonstrated the effect of pollution reduction in a paddy field under controlled drainage.The results indicated that generally speaking, the concentration of NH4+-N and NO2-N in paddy water declined with the persistence of a waterlogged condition.The amount of N leaching under 4 mm/d leakage intensity was nearly two times larger than that under 2 mm/d.Results of ANOVA for N concentration through leaching under two leakage intensities indicate an insignificant difference between the two.Therefore, the main factor that affects N leaching amount is seepage water volume.N losses in surface paddy water declined along with the persistence of waterlogged duration.Compared with traditional drainage, PFCD reduced N loss in surface water by 95.6%, 78.7%, 59.6%, and 87.4% at each of the four growth stages.Surface water exhibited higher N concentration on the first day after the paddy field was waterlogged at each stage, and the loads of N losses in surface water increased on the fourth day after the paddy field was waterlogged at the jointing-booting and milky stage.Therefore,surface drainage should be avoided in those two conditions.