The experiment on soil moisture dynamic and root system growth of Weichang region was conducted. The results showed that: (a) Acuteness of soil water content change was different form soil layer to layer. It was greatly in 80~100cm, less so in 0~20cm, and light below 20~80cm. (b) Root system growth showed a growth pattern in three stubbles, about 75%~95% of root lived at 0~30cm soil layer. (c) Root density showed index movement, the root proportion in 20~30cm soil layer was greatly, which showed that the major root zone was relatively deep in this period. On the summed-up results, Alfalfa use mainly water in top-layer soil; Because the water table is shallow in this period, and the major root is gradually deep, so we should utilize the soil water of the relative steady layer enough, control the number of Alfalfa growth years, then achieve the purpose of “two wins”.
