节水灌溉控制排水条件下稻田水氮平衡试验与模拟

Modeling and experiment of water and nitrogen balance in paddy fields under water saving irrigation and controlled drainage

为了揭示我国南方灌区节水灌溉控制排水条件下稻田水平衡机制及其氮素迁移转化规律,以指导稻田水肥管理,该文以2007-2008年试验区域水稻生长期田间水氮监测数据为依据,基于一阶氮素动力反应方程,耦合田间水平衡及氮素渗漏和作物吸收过程,构建了田间水氮平衡模型,模拟计算了试验区稻田日渗漏水量与各氮素迁移转化过程中的日铵态氮和硝态氮量。结果表明,试验区田间水经渗漏和排水流失占降水和灌溉水总和的54.7%,气态氮素损失(挥发和反硝化)和渗漏是稻田氮素损失的主要途径,挥发和硝化损失量分别占铵态氮和硝态氮的30.6%和36.1%。渗漏流失中硝态氮明显高于铵态氮,排水中铵态氮高于硝态氮。通过渗漏流失的总氮素量亦较大,渗漏硝态氮和铵态氮分别占其相应氮素形态的9.8%和29.5%。因此,减少氮素气态损失有利于提高节水灌溉控制排水稻田氮肥利用率。

In order to investigate the transformation processes of nitrogen in paddy field under water saving irrigation and controlled drainage,experiments of the water and nitrogen measurements were conducted during the rice growth period in 2007-2008.A water and nitrogen balance model was developed on the basis of first order dynamic response equation of physical process of nitrogen.The model was coupled with leakage and nitrogen uptake process and the water balance model in the paddy fields.It was applied with data obtained from two year experiments to simulate the daily water leakage.The daily amount of nitrate and ammonium in all nitrogen transformation process was also calculated.Results showed that 54.7% water of precipitation and irrigation was drained and leaked out of experiment field.The gas losses including volatilization and denitrification and leakage of nitrogen were dominating ways to lose nitrogen in paddy field under water saving irrigation and controlled drainage.The quantity of volatilization and denitrification accounts for 30.6% and 36.1% of nitrogen quantity respectively.Leakage of nitrogen was distinctly more than that of ammonium,while the surface drainage ammonium was more than nitrate.The amount of nitrogen leakage was also considerably high.The ratio of leakage ammonium to the corresponding form nitrogen quantity was 9.8% and that of nitrate quantity was 29.5%.Thus reducing gaseous nitrogen losses is beneficial to improve nitrogen use efficiency in paddy field under water saving irrigation and controlled drainage.