Abstract:Studying on the effectiveness of natural rainfall on the water restoration in the dried soil was conducive to use precipitation rationally, to strengthen the management of the dried soil water, and to promote the effective restoration of the soil dry layers. By setting a large underground soil column in Mizhi test station located in northern Shaanxi, the precipitation and soil moisture content were monitored continuously from 2014 to 2019. And the effectiveness of natural rainfall for the remediation of dry soil moisture was analyzed. The results showed that: (1) From the perspective of water remediation in deep dried soil, rainfall in the semi-arid loess hilly region could be divided into three types: surface layers infiltration with rapid evaporation, shallow layers infiltration with slow evaporation and deep layers infiltration with water recharge. The type of deep layers infiltration with water recharge rainfall was effective, and others were ineffective. The precipitation of this type was usually greater than 26 mm and could effectively recharge water to the deep dried soil. From 2014 to 2019, there were only 16 times of deep layers infiltration with water recharge rainfall, and the cumulative precipitation was 791.8 mm. The precipitation frequency and effective rate were 4.64% and 35.19%, respectively. (2) On a monthly scale, the precipitation (P) showed the quadratic function changes with the monthly infiltration depth (Z) and monthly cumulative infiltration depth (Zaccumulation): Z=-0.0102Pmonth2+3.955Pmonth-6.7335(R2=0.963 9), Zaccumulation=-0.0003Pmonth2-0.1331Pmonth+191.71(R2=0.920 8). (3) On the annual scale, the precipitation from 2014 to 2019 was 187.6, 391.6, 590.8, 337.6, 342.4 and 400.0 mm in sequence. The infiltration depths caused by rainfall year by year were 160, 220, 400, 260, 260 and 120 cm, and the cumulative infiltration depths were 180, 220, 400, 700, 1 000 and 1 400 cm, respectively. The research results played a positive role in revealing the mechanism of natural precipitation restoration of dried soil, strengthening the technology of artificial water storage and soil moisture conservation in the dried layers, selecting the measures of soil moisture conservation rationally and promoting the local ecological environment construction.