半干旱黄土高原地区春小麦地膜覆盖研究概述

在黄土高原半干旱地区春小麦上进行的地膜覆盖试验表明，地膜覆盖通过改善耕层土壤生态环境条件，即通过改善水，热状况，活化土壤养分，对提高水分和养分利用效率，实现粮食增产具有重要作用，但近年来在生产实践和科学实验中发现，不合理的长期全生育期地膜覆盖，因在作物生长前期和中期覆膜作物较不覆膜作物生长好，覆膜作物在生长期水分蒸腾损失严重，土壤水分的蒸散（蒸发＋蒸腾）损失远比不覆膜土壤严重，在作物生长后期降水少或没有补充灌溉时，会产生严重的水分肋迫现象，显著抑制小穗分化和灌浆，最终导致收获得指数和产量下降，同时，地膜覆盖的增产作用在一定程度上是以耗竭土壤肥力，特别是在有机物质为代 的，因此，不正确的地膜覆盖（如全生育期的地膜覆盖），不仅有时起不到显著的增产作用，而且易造成土壤养分，特别是土壤中硝态氮的累积和损失，肥料利用效率降低，土壤生态条件恶化，下降，难以持续高产，因此在确定地膜覆盖范式时，必须要考虑底墒，作物生育期降水，地膜覆盖的阶段性和氮肥的施用等。

Review of clear plastic film mulch on spring wheat in semi-arid loess plateau

The results of plastic film mulching experiments for spring wheat carried out in the semi arid areas on the loess plateau show that plastic film mulching can play a very important role in the aspect of increasing water and nutrient utilization efficiency and in increase of grain yield.Because plastic film mulching can activate soil nutrient by means of improving soil ecological and environmental conditions in the plowed layer,namely,improving water and heat status.But in recent years through production practice and scientific experiments,people increasingly find that irrational and long term plastic film mulching during the whole growth period also cause serious problems:for example,during the early stage and medium stage of crop growth,the crops mulched by plastic film usually grow better than those no mulching plastic film,so during the whole growth stage of former situation more soil water will lose through transpiration,the evapotranspiration (evaporation+transpiration) loss of soil water will be much more serious than that no plastic film mulching,during the late growth period of crops if precipitation is little or no additional water is supplemented to irrigation,this will lead to serious water stress phenomena,and will significantly inhibit small spike differentiation,this finally will lead to decrease of harvest index and crop yields;in the meantime,the yield increase effect under plastic film mulching must be paid heavy cost such as exhaust soil fertility especially organic matter to some extent.Therefore,incorrect plastic film mulching method (for instance mulching plastic film during the whole growth period ) sometimes will not only has no significant yield increase effect,but also easily cause the loss of soil nutrient in particular the loss and accumulation of nitrate in the soil,decreasing the fertilizer utilization efficiency,deterioration of soil ecological condition,decline of soil fertility,and high crop yield will also not maintain sustainable.So deciding the model of plastic film mulching,these factors such as initial soil moisture status,rainfall condition during the growing period,plastic film mulching period after sowing and nitrogen fertilizer application etc must be taken into account.