Study On The Character Of Soil Water Content Under Land Terrancing In Loess Gully-Hilly Areas

The amount of soil moisture is one of the basic elements to determine the occurrence ofagricultural drought.Since the water on crop growth mainly from the soil, study on the law ofsoil moisture movement is the main content on Loess Plateau. The research analyses thevertical change of soil moisture in terrace under different tillage methods and mulchingconditions, and through the Hydrus-1D model in simulated the dynamic change of soilmoisture on the terrace and sloping land of the Loess Hilly. Main achievements are asfollows:(1)The soil water content range is8.89~14.96%,8.29~16.43%,8.17~16.33%respectivelywhen drill,whole plastic-film mulching, whole plastic-unfilm-mulching on wheat,and thevertical variation of drill and whole plastic-unfilm mulching can be divided into three levels:quick change layer， transition layer， supply layer that the soil depth is0~40cm,40~80cm,80~100cm,while whole plastic-film mulching can be divided into quickchange layer and supply layer corresponding0~20cm,20~100cm.(2)The soil water content range is9.53~18.05%,11.70~22.52%,11.77~22.42%,11.48~22.05%,10.57~21.79%,8.81~21.53%,10.51~22.40%respectively wh-enbunch planting, early spring double ridges whole mulching, early spring uncoverring,spring whole mulching, autumn whole mulching, half flat mulching, double film on corn,andits vertical variation can be divided into three levels: quick change layer，transitionlayer,supply layer that the soil depth is0~40cm、40~60cm、60~100cm.(3) The sloping field occurred runoff at23mins in the1.45mm/min rainfall intensity,however, the level terrace had no runoff in the whole process. And in the same conditions,infiltration and soil moisture content in the level terraces are higher than sloping lands’.When it is Rainfall duration for10min, in soil depth of0～15cm, soil water content weremore than terrace slope to0.13%~1.65%, and in the soil depth for30～200cm, terrace andsloping have no infiltration.In soil depth of0~20cm, the terrace of soil moisture of the slope were higher than0.05%~2.22%,0.01%~2%with sloping fields.(4)The soil moisture of terrace for wheat and corn in its growth period can be dividedinto three stage under different tillage methods and mulching conditions,that is slowevaporation stage,rapid water consuming stage and increasing impoundment stage.The timesegment for wheat isOctober to March of the following year, April to May and June,forcorn is April to May, June to July, August to October.(5)The vertical variation of soil moisture on terraces for wheat and corn in0~200cmsoil depth can be divided into four levels: quick change layer,transition layer，supplylayer,graded layer that the soil depth for wheat is0~40cm,40~80cm,80~150cm,150~200cm,for corn is0~40cm,40~60cm,60~100cm,100~200cm.The vertical variation of soil moistureon sloping land for wheat and corn in0~200cm soil depth can be divided into four levels:quick change layer,transition layer，supply layer,graded layer that the soil depth for wheat is0~20cm,20~90cm,90~120cm,120~200cm, for corn is0~40cm,40~60cm,60~90cm,90~200cm.The Hydrus-1D model in simulated the soil moisture change of wheat andcorn within0~200cm soil depth，can be divided into two stages:slowly water consumingstage and violent change stage.In slowly water consuming stage,the spring wheat includesspring defrosting-sowing(mid-March to early-April) and autumn harvest-freezing(late-August to mid-October)stage,the summer corn includes spring defrosting-sowing(January to April)and winter freezing stage(November to December).In violent changestage,the spring wheat includes rapid water consuming (mid-April to early-June) stage andincreasing impoundment stage (mid-June to July),the summer corn includes increasingimpoundment stage (early-June to mid-July)and rapid water consuming stage(August toearly October).