In order to investigate the effects of different water regulations on the root spatial distribution

water consumption

water use and other indexes in a typical alley cropping system comprising apple (Malus pumila)-soybean (Glycine max)

an experiment of mulching and irrigation coupling was carried out in the Loess Plateau of Shanxi Province. Three levels of irrigation thresholds were set:55% (low

W1)

70% (medium

W2)

and 85% (high

W3) of field capacity. Meanwhile

two mulching materials including straw (M1) and plastic film (M2) were also set. The results indicated that the water regulation increased the total root length density of apple and soybean

and also expanded the root length distribution of apple in horizontal and vertical directions. The apple root length density was negatively correlated with the distance from the tree row while the soybeans had positive correlation

and both the crops had negative correlations with the vertical depth. The distribution of soil moisture increased first with the distance from trees to the crops then decreased at grain filling stage

and the minimum values occurred in the distance of 1.5~2.0 m away from the tree line. Compared with clean tillage treatment (CK0) and single mulching treatment (CK1 and CK2)

the water regulation treatments increased the soil moisture in 0-60 cm depth significantly. The cluster analysis showed that the main competition area in soil moisture for the two plants was in the distance 0.5~1.5 m away from the tree row with soil depth of 0-40 cm. The apple fine roots in the M2W2 treatment were concentrated in 20-40 cm soil layer while the soybeans' in 0-20 cm soil layer

which alleviated water competition between the two species. Additionally

the water consumption in M2W2 could be reduced by 40~50 mm compared with W3 and the yield and water use efficiency could be increased by 29.37%~41.92% and 12.29%~53.35%

respectively

compared to other water regulation treatments. The net income could be 2 976.5 yuan/hm2. Above all

covering plastic film in young apple-soybean intercropping system

combined with irrigation amount of 150 m3/hm2 at branching stage

400 m3/hm2 at podding stage and 300 m3/hm2 at grain filling stage could significantly increase the water use level and economic benefits in the intercropping system.