施磷对稻田土壤及田面水磷浓度影响的模拟

通过施用不同剂量磷肥稻田土壤淹水培养试验，研究了施磷对稻田土壤及田面水磷浓度的影响.结果表明，土壤速效磷（Olsen-P）浓度在施磷后迅速下降，60 d后趋于稳定.随施磷量的增加，土壤速效磷和缓效磷库量均递增，Olsen-P与施磷量呈正相关关系(y=21.49+0.086x)，表明该土壤有很高的固磷潜力.施磷后田面水中全磷浓度呈先迅速上升后又缓慢下降趋势，施磷120 d后，田面水中全磷浓度与施磷量呈指数相关关系(y=0.3 72e^0.0022x)，施磷量在400～800 kg·hm^-2之间田面水全磷浓度加速增长，如果施磷量达到或超过800 kg·hm^-2，则磷容易进入田面水并导致流失，低于该施磷量时，则磷进入田面水中的量较少.利用分段回归模型模拟土壤Olsen-P与水面全磷关系，预测出导致田面水中磷激增的土壤Olsen-P浓度“突变点”为82.7 mg·kg^-1，即施磷量为712 kg·hm^-2.因此，土壤Olsen-P浓度可作为预测田面水中磷损失程度的指标.

Effects of P application on P concentrations in paddy soil and its surface water: A simulation test

An anaerobic incubation test was conducted to study the effects of different P application rate on the P concentrations in paddy soil and its surface water. The results showed that soil available P (Olsen-P) decreased rapidly at the beginning, but approached to stable after 60 days of P application. Both Olsen-P and residual P increased with increasing P application rate, and Olsen-P had a positive correlation with P application rate, suggesting that the test soil had a strong P adsorption capacity. After P application, the total P (TP) in soil surface water increased rapidly, and then decreased slowly, showing that there was a P exchange between soil and its surface water. After 120 days of P application, there was an exponential relationship between soil surface water TP and P application. The TP in soil surface water increased rapidly when the P application rate was 400 - 800 kg x hm (-2) , and easy to be lost when the P application rate was higher than 800 kg x hm(-2). The simulation with split line model on the relationship between soil Olsen-P and soil surface water TP showed that the change point of soil Olsen-P, which induced a sharp increase of soil surface water TP concentration, was 82. 7 mg x kg( -l) , corresponding to a P application rate being about 712 x kg hm(-2). Soil Olsen-P could be a good indicator in forecasting the P loss from soil surface water.