典型双季稻田施磷流失风险及阈值研究

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),k0)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)。

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

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 5474~5552 kg·hm^-2 and 7096~7521 kg·hm^-2 during 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·e^k/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^-2 and (56.87±7.90) kg P₂O₅·hm^-2 for the early and late rice,respectively,in southern China.