氮肥施用对黄土高原中部雨养农业区土壤硝态氮分布与累积的影响

Effects of Nitrogen Rate on the Distribution and Accumulation of Soil Residual Nitrate in the Rain-fed Agricultural Region of the Middle Loess Plateau

黄土高原中部雨养农业区春小麦氮肥试验表明,氮肥施用量对土壤硝态氮的移动深度没有影响,但显著影响土壤硝态氮的含量与累积。连续施氮3年后第3季春小麦收获时,0～200cm土壤剖面中累积大量的硝态氮,其中48.96%～81.38%的总累积量和60.49%～122%的当年净累积量存在于0～110cm土层中。在确定春小麦适宜施氮量时应考虑到0～110cm土层中残留硝态氮的累积量。不施氮和氮磷比例为1:1时,连续施氮三年后土壤硝态氮总累积量最低,数量几乎相等;第3季春小麦收获后较播种时,土壤硝态氮发生亏缺。施氮量为52.5 kgN hm-2时土壤硝态氮的三年总累积率和第3季春小麦当年的净累积率居各处理之首(146.55%和138.21%)。合理的氮磷配比可有效减少土壤硝态氮的累积,不合理的氮磷配比下,低施氮量也会造成土壤硝态氮的大量累积。

The purpose of this study was to determine the effects of nitrogen rate for spring wheat on soil residual nitrate distribution and accumulation in 0-200cm soil depth profile in the rain-fed agricultural region of the middle part of loess plateau. The experiment was conducted by using urea at five rates ranging from 0 N to 210Nkg hm-2 combined with 105 P2O5Kg hm 2 in March, 2003. Before and after wheat harvest, the soil was sampled to a depth of 200cm and analyzed for nitrate nitrogen. It was found that nitrogen rate had no effect on nitrate movement in the soil after 3 years, i. e. residual nitrate did not move beyond 200cm in all treatments. However, nitrogen rate influenced the residual nitrate amount and accumulation in the soil significantly. After 3-year continuous application of nitrogen fertilizer, 48.96%-81. 38% of the total and 60.49%-122% of the net increase were accumulated in the O-110cm profiles. When the nitrogen rate is 52.5Nkg hm^2, all nitrate accumulation after 3 years accounted for 146.55% of the total.