华北山前平原农田土壤硝态氮淋失与调控研究

Soil nitrate leaching and control methods in the piedmont of North China Plain

本文依托中国科学院栾城农业生态系统试验站小麦-玉米一年两熟长期定位试验,应用土钻取土和土壤溶液取样器取水的方法,研究了不同农田管理措施下土壤硝态氮的累积变化,计算了不同氮肥处理通过根系吸收层的硝态氮淋失通量。结果表明,小麦-玉米生长季土壤硝态氮累积量和淋失量随着施氮量的增加显著增加,相同氮肥水平下增施磷、钾肥增加了作物的收获氮量,施磷肥增加的作物收获氮量最高可达123 kg.hm-2.a-1,施钾肥增加的作物收获氮量最高为31 kg.hm-2.a-1。不同灌溉水平下0-400 cm土体累积硝态氮随着灌溉量的增加而降低,控制灌溉(小麦季不灌水,玉米季灌溉1水)、非充分灌溉(小麦季灌溉2-3水,玉米季按需灌溉)、充分灌溉(小麦季灌溉4-5水,玉米季按需灌溉)各处理剖面累积硝态氮量分别为1 698 kg.hm-2、1 148 kg.hm-2和961 kg.hm-2。与非充分灌溉和充分灌溉处理相比,控制灌溉在100-200 cm土层硝态氮累积量显著高于其他层次,2003-2005年间控制灌溉剖面增加的硝态氮量占施肥总量的23%;非充分灌溉处理剖面增加的硝态氮量占施肥总量的22%;充分灌溉处理剖面增加的硝态氮量占施肥总量的47%。免耕措施降低了作物产量,影响土壤水的运移,增加了硝态氮的淋失风险。根据作物所需降低氮素投入(N 200 kg.hm-2.a-1),增施磷、钾肥,控制灌溉量是减少华北山前平原地区硝态氮淋失,保护地下水的有效措施。

Soil core and soil water samples were collected in a long-term field experiments to study soil nitrate nitrogen（NO3--N） accumulation and leaching in winter wheat/summer maize double-cropping system under different agricultural management practices in the North China Plain（NCP）.The results showed that NO3--N accumulation in the soil profile and NO3--N leaching through the root zone increased with increasing N fertilizer application（P0.05）.Application of P and K fertilizers improved the grain yield and harvested more N in grains.P and K inputs increased the amounts of harvested N in grains by 123 kg·hm·2-a-1 and 31 kg·hm-2-a-1,respectively.Based on the experiment,the amount of irrigation also affected NO3--N accumulation and distribution in the soil profile.The amounts of accumulated NO3--N in the 0-400 cm soil profile significantly decreased with increasing irrigation frequency.Arid irrigation treatment（i.e.,no irrigation and one irrigation during winter wheat and summer maize seasons,respectively） produced 1 698 kg（N）·hm-2 of accumulated NO3--N in the 0-400 cm soil profile.This was significantly higher（P 0.05） than those of deficient irrigation（i.e.,2-3 irrigations during winter wheat season,irrigation when needed during summer maize season） and sufficient irri-gation（i.e.,4-5 irrigations during winter wheat season,irrigation when needed during summer maize season） with accumulated NO3--N in the 0-400 cm soil profile of 1 148 kg（N）·hm-2 and 961 kg（N）·hm-2,respectively.Compared with deficient and sufficient irrigation treatments,accumulated NO3--N in the 100-200 cm soil layer was higher than in the other soil layers under arid irrigation treatment.From 2003-2005,increases in NO3--N in the 0-400 cm soil profile were different among different irrigation treatments.The amounts of fertilizer N left in the soil under arid irrigation,deficient irrigation and sufficient irrigation were 23%,22% and 47%,respectively.No-tillage decreased grain yield,changed soil water movement and increased water storage in deep soils,which in turn increased the risk of NO3--N leaching.Based on the results,200 kg·hm-2-a-1 N input with less irrigation and balanced fertilization were the most effective mode that protected groundwater from nitrate pollution in NCP.