黄土高原旱地小麦长期施氮的效应

为了解黄土高原旱地小麦的长期施氮效应，以1984年以来开展的长期定位肥料试验为基础，在一定施磷量（39.3 kg·hm^-2）下，分析了长期不同施氮水平（0、45、90、135和180 kg·hm^-2）间小麦产量、氮素利用、养分累积和土壤氮素含量的差异。结果表明，长期施用氮肥对提高小麦产量仍有显著作用。氮肥利用率和利用效率均随着施氮量增加呈现显著降低的趋势，但施氮135 kg·hm^-2高于90 kg·hm^-2或二者差异不显著；施氮显著提高了小麦籽粒、秸秆和植株对氮、磷、钾的累积量，同时有利于养分在籽粒中的分配；土壤氮素累积量随施氮量增加呈现先升高后降低趋势，全氮和碱解氮含量均在施氮135 kg·hm^-2达到最高值或较高值。黄土高原地区小麦施氮135 kg·hm^-2时，可以获得较高产量，同时氮肥利用效率、籽粒中养分累积量及土壤残留氮量也较高，是该地区小麦氮素最适施用量。

Effects of Long term Nitrogen Fertilization on Wheat in Loess Plateau

Based on the long term fertilization experiment in Loess Plateau that started in 1984, the effects of long term nitrogen fertilization (0, 45, 90, 135 and 180 kg·hm^-2) on wheat were studied under certain amount of phosphate fertilizer (39.3 kg·hm^-2) application. The results showed that: Long term application of nitrogen fertilizer still had significant effect in increasing wheat yields; Nitrogen use efficiency decreased significantly with increasing of nitrogen fertilizer amount, but that of 135 kg·hm^-2 was higher than that of 90 kg·hm^-2, or there was no significant difference between them; Nitrogen application increased significantly the accumulation of nitrogen, phosphorus and potassium in wheat grain, wheat straw and wheat plant, and was contribute to the distribution of nutrients to grain; Accumulation of soil nitrogen was increased first and then decreased with the increasing of nitrogen amount, and total nitrogen content and available nitrogen content reached the highest value or the second highest value in 135 kg·hm^-2; Nitrogen fertilization of 135 kg·hm^-2 was the most appropriate amount for wheat in Loess Plateau, because higher yield, higher nitrogen use efficiency, higher nutrient accumulation and higher soil residual nitrogen could be achieved.