Soil water environment of the Prunus armeniaca-Astragalus system in hill-gully area of the Loess Plateau

Based on the Prunus armeniaca-Astragalus system in hill-gully area of the loess regions in Zhongyang county, Shanxi Province, the soil moisture benefits of the Prunus armeniaca-Astragalus system on the terrace field after Astragalus intercropped in Prunus armeniaca orchard two years had been studied. The soil water content and storage in the profile measured by oven dry method in 2004 and 2005. This study was intended to provide theoretical basis in forestry structure design and optimization models for fruit tree-herb system and forestry ecological construction in the region. Results show that the main yearly tendency of soil water storage within 0～150 cm soil layer of the Prunus armeniaca-Astragalus system is similar to which of planting apricot without covering. And they are similar to the change of yearly precipitation. But the soil water storage within 150 cm soil layer of the Prunus armeniaca-Astragalus system in 2004 and 2005 is 2917 mm and 2887 mm, and higher than the planting apricot without covering 387 mm and 393 mm, respectively, about increased 15.3％ and 15.8%. The effect is more significant during the main rainfall season(July-September), the soil water storage within 150 cm soil layer of the Prunus armeniaca-Astragalus system during the main rainfall season in 2004 is higher 152 mm than the planting apricot without covering, and which is 163 mm in 2005. The tendency changes of the contour map of the soil water content within 150 cm soil layer in agroforestry system is similar to the planting apricot without covering. But the grads change in agroforestry system is smaller than that in planting apricot without covering, and the soil water content is comparatively steady in profile. The 0～150 cm soil layer moisture under crown of tree of the Prunus armeniaca-Astragalus system is also better than the planting apricot without covering. The average soil water content distanced tree 30 cm of the Prunus armeniaca-Astragalus system is higher the planting apricot without covering 2.13％～3.51％, and which is 2.08％～3.18％ of the average soil water content distanced tree 60 cm. The Prunus armeniaca-Astragalus system can improve the soil water status of orchard.