不同氮肥用量下冬小麦土壤剖面累积硝态氮及其与氮素表观盈亏的关系

摘要

More than 20 field experiments designed with the ＂3414＂ plan were carried out in Huxian County and Zhouzhi County,Guanzhong Plain,Shaanxi during 2008 and 2009 to evaluate the nitrate nitrogen（NO3-N） accumulation in soil profiles after harvesting winter wheat;and its relationship with the apparent N budget in soil was also studied.The results show that the amounts of NO3-N accumulation in the soil profiles and their extents to leach into the deeper soil layers are increased significantly as the nitrogen fertilizer usage increased.When the N fertilizer rate reaches to 180-240 kg/ha,positive budget of nitrogen in soil is observed in some experiment sites,and when N fertilizer rate reaches to the 270-360 kg/ha,positive budget of nitrogen in soil is observed in all experiment sites.There is a positive correlation between the apparent balances of soil N and the accumulation of NO3-N in soil profiles（0-2 m）.This indicates the amount of NO3-N in the soil profile is mainly determined by the apparent N budget balances in soil.The NO3-N accumulation in the soil profile is increased about 62.5 kg/ha with each 100 kg/ha increase of apparent N budget in soil.%以在陕西关中地区户县、周至两县连续2年的20余个＂3414＂肥料田间试验为研究对象,研究了不同施氮量下冬小麦收获后土壤2 m剖面硝态氮的分布、累积及其与土壤氮素表观盈亏量间的关系。结果表明：随着氮肥用量的提高,土壤剖面硝态氮累积量明显增加,其向土壤下层淋溶的程度也越严重;当施氮量为180～240 kg/hm2时,一些试验点的土壤氮素已经表现出盈余;当施氮量达到270～360 kg/hm2,所有试验点土壤氮素均明显盈余。不同施氮量时土壤表观氮素平衡值（施氮量与氮素携出量的差值）与土壤0—2 m剖面硝态氮累积量之间呈极显著正相关,说明土壤表观氮素平衡和盈亏决定了土壤剖面硝酸盐的累积状况;土壤氮素表观盈余值每增加100kg/hm2,0—2 m土壤剖面硝态氮累积量增加约62.5 kg/hm2。