不同氮磷配合下稻田田面水的氮磷动态变化研究

Dynamic Changes of Nitrogen and Phosphorus Concentrations in Surface Water of Paddy Field

稻田田面水中N、P浓度是决定稻田N、P径流流失，N素的氨挥发与硝化-反硝化等各种损失途径的关键因子。采用田间试验方法研究了不同N、P配合下田面水中N、P动态变化。结果表明，田面水总N（TN）、总P（TP）和溶解态无机P（DIP）的浓度在施肥后很快达到峰值，之后迅速下降，其变化均可以用指数方程（Y=C0×e^-k t）来描述。NH4^＋-N在施N后2～4天达到峰值，之后逐渐下降，6—7天后降至稳定。基肥施用后的NH4^＋-N浓度上升比分蘖肥和孕穗肥施用后慢，同时TN和NH4^＋-N浓度下降也慢。相同施N水平下，高P处理田面水的NH4^＋-N和TN浓度较优化处理高：相同施P水平下，高N和低N处理田面水的TP和DIP浓度也较优化处理高，这表明：当N、P其中之一超过或低于适合用量时，会促进另一养分的流失。施肥后田面水中TN、TP和DIP可作为稻田N、P流失的主要指标，应着重控制基肥施用后N、P的径流流失。以及追肥施用后尿素的水解速度。

A field experiment was conducted to study dynamic changes of NH4^＋-N, TN, TP and DIP concentrations in surface water of paddy fields applied with different combination of N and P fertilizers. Results showed that TN, TP and DIP reached their respective peak values in concentration quickly after urea and superphosphate applied, and then soon decreased which fits an exponential equation, （Y =Coxe^-k t ）, while NH4^＋-N peaked 2-4 days after urea applied, and decreased soon afterwards, and then leveled off after another 6-7 days. NH4^＋-N concentration rose much slower after basal dressing than after side-dressings at the tillering and milking stages, and the decrease of NH4^＋-N and TN concentrations was lower, too. With the same level of N fertilization, NH4^＋-N and TN concentrations in the surface water were higher in Treatment HP than Treatment OPT, while with the same level of P fertilization, TP and DIP concentrations were higher in Treatments HN and LN than in Treatment OPT, indicating that either N or P being too high or too low in application rate may accelerate loss of the other one. TN, TP and DIP could be cited as key parameters for N and P runoff loss within 3 days after urea application. A week after fertilization was the critical period for controlling loss of N and P from paddy fields.