不同氮磷配合下稻田田面水的氮磷动态变化研究

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-kt)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。

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

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=C₀×e^-kt), 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.