典型双季稻田施磷流失风险及阈值研究

Research on P loss risk and threshold value in typical double-cropping rice field

通过3年(2011—2013年)的双季稻田间小区试验,探明了不同施磷量对双季稻产量、土壤磷素积累、磷素流失风险的影响,并确定了土壤收支平衡的施磷阈值。研究结果表明:连续3年不同施磷量处理水稻早、晚季产量为5474~5552 kg·hm^(-2)和7096~7521 kg·hm^(-2),过量施用磷肥对水稻产量无显著增产效果,反而有减产的风险。施用磷肥后,土壤Olsen-P含量显著提高。田面水TP平均浓度与土壤中Olsen-P呈显著正相关关系;施磷后田面水磷素动态能用指数模型(Y=C_0·e^(k/t),k>0)拟合,即随着磷肥施用量增加,田面水磷素流失风险增加。结合水稻产量效应、土壤磷素表观平衡和磷素环境风险,推荐研究区域早、晚稻施磷阈值分别为(48.53±7.07)kg P_2O_5·hm^(-2)和(56.87±7.90)kg P_2O_5·hm^(-2)。

Effects of different rates of phosphorus（P）application on the grain yield, soil P accumulation, and risk of P loss through surface runoff were studied in double-cropping rice fields to determine the threshold values of the optimal P fertilizer application rates, using the field plot experiments during 2011—2013. The results showed that average yields of the early and late rice were 54745552 kg·hm-2and70967521 kg·hm-2during the 3-year observation period, respectively, and excessive P fertilizer application did not significantly increase the rice yields, but in fact increased the risk of yield reduction. P fertilizer application significantly increased soil Olsen-P contents. The average total-P（TP）concentrations in the surface water of rice fields showed a significantly linear relationship with the soil Olsen-P contents.The dynamics of P concentrations could be simulated using the exponential model（Y=C0·ek/t,k〉0）, suggesting that the risk of P loss through surface runoff would elevate with the increasing P fertilizer application rates. Considering the effects of P fertilizer application on rice yields,soil P surplus, and environmental risk of P loss, the recommended threshold for the optimal P fertilizer application rates were estimated to be（48.53±7.07）kg P2O5·hm-2and（56.87±7.90）kg P2O5·hm-2for the early and late rice, respectively, in southern China.