减肥措施对稻田田面水氮、磷动态变化特征的影响

Effects of Dynamic Changes of Nitrogen and Phosphorus Concentrations in Surface Water of Paddy Field Under Different Fertilizer Rate

我国水稻种植面积大,过量施肥后稻田氨挥发、氮磷径流和渗漏等途径会引起农业面源污染等问题,而水稻淹水阶段田面水中氮、磷浓度是关键控制因子。通过设置田间小区隔板,开展肥料减量试验,研究稻季田面水不同形态氮、磷动态变化特征,同时探讨其潜在的环境效应。结果表明,磷肥施入后田面水总磷(TP)、总可溶性磷(TDP)和颗粒态磷(PP)浓度均呈先升高后降低趋势,9 d内下降迅速;基肥施入9 d,当氮、磷水平分别为214、90kg·hm^(-2)时,TP、TDP和PP质量浓度分别为0.76、0.71和0.03 mg·L^(-1);晒田结束后,田面水中TP和TDP浓度出现1次回升。各处理铵态氮和硝态氮浓度分别在基肥施入后第2天和第5天达到峰值;当施氮量为214、182和162 kg·hm^(-2)时,田面水铵态氮浓度分别为对照的15.83、9.16和7.86倍,5 d内铵态氮浓度下降迅速且不同施肥处理间差异趋同。此外,增施氮磷肥料并不能显著增加水稻产量,当氮、磷水平分别为214、90 kg·hm^(-2)时,水稻产量反而降低。因此,提出施磷后9 d内和晒田复水后是控制田面水磷流失的关键时期,而控制氮损失的关键时期是施肥后5 d内。综合水稻产量和肥料农学效率,证实试验田氮肥或磷肥减量25%是可行的,但仍需进一步通过大田试验验证其产量的持续性。

Rice is broadly planted in China.Ammonia volatilization,nitrogen(N)and phosphorus(P)runoff and leakage have caused agricultural non-point source pollution and other issues due to excessive fertilization.The concentration of N and P in surface water during the flooding period is the key control factor.The dynamic characteristics of N and P in surface water of paddy field and their potential environmental impact were studied by field experiment with different P and N application.The results show that the concentration of total P(TP),total dissolved P(TDP)and particulate P(PP)all increased rapidly within 9 days after P application and then decreased.The concentrations of TP,TDP,and PP reached 0.76,0.71 and 0.03 mg·L-1 with 214 and 90 kg·hm-2 N and P application,respectively.Besides,the concentration of TP and TDP showed an obvious rise after the soil-drying period.The concentration of ammonium nitrogen and nitrate in all treatments reached to maximum in 2 and 5 days,respectively,after the application of basal fertilizer.The concentration of ammonium nitrogen with 214,182 and 162 kg·hm-2 of N application were 15.83,9.16 and 7.86 times of that in control treatment.N concentration decreased rapidly after 5 days and the differences between treatments became much smaller.In addition,increasing N and P application amount did not significantly increase the rice yield,but inversely,rice yield decreased with 214 and 90 kg·hm-2 of N and P application,respectively.Therefore,9 days after P application and the stage after rewetting were the key periods for controlling P losses through runoff in surface water from paddy field,while 5 days following N application is the vital period for controlling N losses.By considering both rice yield and fertilizer agronomic efficiency,it is feasible to reduce 25%of N and P application.However,this should be further investigated for high yield consistency through field experiment.