A real-time rainfall control technique consisting of artificial rainfall-shields and gravitational trickle irrigation system was used to investigate the effects of normal rainfall (CK),rainfall reduction 1/3 (R-1/3),and rainfall increase1/3 (R+ 1/3)) on 0 ～ 4 m soil water storage,winter wheat water consumption and WUE in the loess tableland.The results indicated that:(1) Rainfall fluctuation modified water utilization of winter wheat and soil water supply.With the reducing of rainfall,winter wheat used more soil water,resulting in the decrease of deep soil water content during growth and fallow periods,which was hardly restored by rainfall during fallow period.With the increase of rainfall,deep soil water content decreased during growth period but could be restored even higher than initial soil water content after harvest due to the supply of rainfall in fallow period.(2) Winter wheat used soil water that transformed from current rainfall event firstly and then used early soil water.For evapotmnspiration(ET) of the period from overwintering to mature period,winter wheat of R-1/3 used more soil water from 0 to 2 m.Precipitation(P) and △W0～2 m each accounted for about 40％ of the ET.The ratio which P accounted for in ET of R+ 1/3 was about 1 times more than AWo～2 m· However,in the treatment of CK,The proportion which P accounted for in ET was about 15％ more than △W0-2m.Under the condition of rainfall decrease,the proportion of soil water transformed from current rainfall event to winter wheat water consumption decreased and the proportion of 0～ 2 m early soil water increased.Opposite result was obtained with rainfall decreasing.(3) Campared with CK,the winter wheat WUEbio(on biomass level) decreased by 1.3％ in the treatment of R-1/3,and its WUEgran(on grain level) increased,because the decline on grain level(7.1％) was less than the degree of water drops(14.2％).The winter wheat biomass decreased by 5.3 ％ and grain yield increased by 4.5 ％ in the treatment of R+1/3 when it was harvested,but its WUEbio and W UEgrain decreased because of 11.4％ increase in soil water conumption.Generally,rainfall fluctuation had effects on soil water use,soil water supply,winter wheat water consumption composition and the balance between biomass and grain of winter wheat,which affected the winter wheat WUE finally.%采用人工遮雨棚和自流滴灌系统来实时人工干预降水,研究了黄土塬区不同降水条件即正常降水(CK)、降水减少1/3(R-1/3)和降水增加1/3(R+1/3)条件下,麦田0～4m土壤水分变化、冬小麦耗水特性及WUE.结果表明:(1)降水变化改变了冬小麦对土壤水的利用和补给;降水减少,冬小麦对土壤水的利用增强,导致生育期和休闲期深层土壤含水量降低,且很难补充恢复;降水增加,冬小麦也会部分利用深层土壤水,土壤含水量在生育期呈降低趋势,在冬小麦收获后,土壤水得到补给,土壤含水量会逐渐恢复并高于前期土壤含水量.(2)冬小麦优先利用降水转化而来的土壤水,然后利用土壤前期储水;对于越冬～成熟期的总耗水量(ET)组成,R-1/3处理的冬小麦对降水和0～2m土壤水分的利用增强,降水量(P)和0～20m土壤贮水变化量(△W70-2m)各自约占ET的40％;R+1/3处理P占ET的比例约是△W0～2m的1倍多;CK处理P占ET的比例比△W0-2 m高15％左右;降水减少,降水占耗水量的比例降低,0～2m土壤水占耗水量比例增加;降水增加,则有相反的结果.(3)降水减少,WUEbio (基于生物量的WUE)相对于CK处理降低了1.3％,但产量下降程度(7.1％)小于耗水下降程度(14.2％),WUEgrain(基于籽粒产量的 WUE)反而增加;降水增加,相对于CK处理生物量减少5.3％而籽粒产量增加4.5％,但水分的消耗增加了11.4％,WUEbio和WUEgrain均降低.总之,降水变化改变了冬小麦对土壤水的利用、土壤水的补给、冬小麦的耗水组成以及生物量和产量的平衡,最终影响冬小麦WUE.
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