根据设在黄土高原沟壑区旱塬地的长期田间定位试验结合野外调查,对旱塬人工草地土壤0～1000cm水分含量及剖面氮素含量与分布进行研究。结果显示,旱地人工草地连续种植会显著消耗土壤深层储水与土壤氮素,苜蓿的耗水深度超过1000cm,剖面200cm以下平均含水量12.6%;同时,也使深层土壤硝态氮含量降低,150cm以下硝态氮含量均小于1mg/kg,荒草地的水分状况好于人工草地,这是因为荒草地的生物量远低于人工草地,200cm以下平均含水量18.8%。在干旱地区,土壤深层储水可以调节植物用水,但是人工苜蓿从土壤深层吸收大量水分导致土壤干燥化的发生。因此,土壤储水的调节作用丧失,合理的草地产量是控制土壤干燥化的途径。草地施肥并没有显著的增产作用,但可以延缓人工草地的衰退时间。因为草地施肥的效益不明显,生产实践中农民并不施肥。

According to a long term experiment in dry land of the Loess Plateau and field survey of wilderness,we studied the distribution of soil water and nitrogen content in the soil profiles.The results showed that artificial meadow could consume lots of soil water in deep layers of soil,and it also absorbed much of nitrogen.The mean soil water content of200cm～1000cm soil layers was12.6%,furthermore,the nitrate content of150cm～1000cm soil layers was less than1mg /kg.But soil water content of the wilderness was better than that of artificial meadow;the mean soil moisture was18.8%.In the arid area,the storage water in deep layers of soil can adjust water utilization of plants,but artificial alfalfa can absorb lots of water from deep layers and lead to soil desiccation.Because of in availability of enough water to adjust effects of arid weather on growth of plants,reasonable yield should be advised to control soil desiccation.Fertilizers application can not contribute to yield of grassland distinctly,but it can maintain output of artificial alfalfa to avoid the yield getting down in the short time.Unfortunately,fertilizers were not used in grassland by farmers,because it is difficult to profit from fertilizers application.