| In order to explore the soil moisture characteristics of deep roots and perennial plants under the background of deep soil desiccation in loess hills. The results showed that: 1) The diurnal variation of soil moisture slowed down with the increase of depth, and remained basically unchanged in the 40 cm soil layer, and the occurrence time of the maximum and minimum values of diurnal soil moisture was gradually delayed from May to October. 2) Under the background of deep soil drying, the soil moisture in the first year of replanting alfalfa was mainly deposited, and the savings were mainly concentrated in the 0-340 cm soil layer, and the water recovery in the soil dry layer reached 68% of the field water holding capacity, and the recovery depth reached 290 cm. In the second and third years of alfalfa planting, soil moisture was mainly consumed, and the effective soil water storage was basically depleted in the third year of alfalfa planting. 3) There were no significant differences in yield and water use efficiency between the first and second years of replanting alfalfa compared with the control (P>0.05), and there was a significant difference in yield in the third year compared with the control (P<0.01), but there was no significant difference in water use efficiency (P>0.05). This study can provide a scientific basis for the sustainable replacement of artificial vegetation and the rational utilization of water resources in the loess hilly area. |