黄土高原农田水量平衡研究

Study on Field Water Balance of Loess Plateau

黄土高原由北向南顺序分布有沙壤带、轻壤带、中壤带和重壤带；２ｍ土层最大持水容量约相当于各自所处地区的年降水量；２ｍ土层有效持水容量约相当于各自作物耗水量的７０％以上。黄土高原农田水分主要来源是降水，主要支出是作物蒸腾和土壤蒸发。巨大的土壤水库可容纳全部降水而且截留在作物可利用层之内。约有７０％～８０％的水量消耗于作物生长期的蒸发和蒸腾；约有２０％～３０％的水量消耗于非生长期的蒸发。北部地区作物（谷子、马铃薯）耗水量约３００ｍｍ；南部地区作物（冬小麦、春玉米）耗水量约４５０ｍｍ。裸露农田土壤蒸发在雨季时最强烈，北部地区雨季时农田土壤蒸发量占同期降水量的９０％，南部地区占６３％。土壤水分入渗深度由北向南为１．０～２．５ｍｍ作物耗水层深度主要在２ｍ以内。

The sand,light,medium,and heavy loam are distributed over Ioess Plateau from northto south,The maximum water capacity in 2m sod depth approximately equals to the annual precipi-tation of each region ,and the maximum available water capacity is over 70%of water consumptionof crop in each region. In Loess Plateau,the main water resource is precipitation,and main waterexpenditure is evaporation and plant transpiration. The gigantic soil reservoir can receive all of rain-fall and reserve it within soil zone of plant absorption. About 70%一80%of water is used in evapo-transpiration during growth peried. and about 20%一30%is wasted due to soil evaporation duringnon-growth peried. The water consumption(Millet,Potato)in northern region is ahout 300mm,andin the southern regin(winter wheat,spring corn)is ahaut 450mm。Rainy season is the most vio-lent season for bare soil evaporation. In northern region the evaporation amount accounts for 90%ofrainfall in rainy season,and in southern region accounts for 63%。The depth of water redistributionin soil varies from 1.0m to 2.5m from north to south,and the soil depth of water use by plant ismaiuly within 2m。