中文摘要：

通过在陕西关中平原地区连续7年的田间定位试验,分析比较了3种地表覆盖模式（常规、覆草、覆膜）下不同施氮水平（N 0、120、240 kg/hm^2）对冬小麦产量及土壤肥力的影响,旨在为半湿润易旱区旱作农业选择合理的栽培组合提供依据。结果表明,2002～2009年覆草处理小麦产量平均减产1.46%,覆膜增产7.04%,施用氮肥平均增产42.72%,而N240与N120处理间无显著差异。试验进行第7季后对土壤肥力有如下影响：覆草及覆膜处理下土壤活性有机碳含量较常规分别增加37.57%、21.39%;覆草亦显著提高土壤有机碳、全氮、速效钾含量,较常规分别增加6.84%、4.40%、12.68%,而覆膜作用不显著。施氮量主要影响土壤活性有机碳、矿质氮、速效磷及pH值,施氮较不施氮依次增加6.03%、40.18%、-23.55%、-0.05个pH单位,与N120处理相比,N240处理对土壤矿质氮及pH值影响不显著。综上,在研究区一年一作条件下,覆草或覆膜处理增产潜力有限,但覆草配施适量氮肥模式具有明显增加土壤有机碳和速效钾含量的效果,亦对提高石灰性土壤养分有效性具有重要作用。

英文摘要：

To determine reasonable cultivation mode for dry farming practice in the semi-humid prone to drought region, the effects of surface mulching and N addition on winter wheat yield and soil nutrients regimes were compared. The experiment was conducted during the seven consecutive years of 2002-2009 in Guanzhong Plain of Shaanxi province. The nine treatments consisted of three levels of mulching, namely, no mulching （ NM）, wheat straw mulching （WSM）, plastic film mulching （PFM）, and three nitrogen levels （N 0, 120 and 240 kg/ha）. Soil samples were collected after wheat harvest in 2009 of a winter wheat-summer fallow system. In addition, wheat yields were also considered in the growing seasons of 2002-2009. The results showed that the yield was averagely decreased by 1.46% in the WSM treatment, and increased by 7.04% in the PFM treatment compared to the NM treatment of consecutive seven years. Moreover, the yield was averagely increased by 42.72% in the two nitrogen amended treatments compared to the no nitrogen addition treatment during 2002 -2009, however, no significant differences between N application of 120 and 240 kg/ha treatments were found. Comparing with NM treatment, soil labile organic C content at the surface layer was significantly increased by 37.57% and 21.39% in the WSM and PFM treatments, respectively. In contrast with PFM, a significant increase of 6.84% , 4.40% and 12.68% in soil organic C, total N and available K was observed in WSM treatment, respectively. Soil labile organic C and mineral N were averagely increased by 6.03%, 40. 18%, and available P and pH value were decreased by 23.55% and 0. 05 pH unit in the two N amended treatments compared to the NO treatment. In other words, these four soil parameters were significantly sensitive to different N rates. But there were no significant differences of mineral N and pH value between N120 and N240. In conclusion, there are no advantages on yield of WSM and PFM treatments in this experiment. Meanwhile, the planting mode of WSM combi