In order to explore the optimal integrated management system of water and fertilizer under drip irrigation in a fruit-crop intercropping system in the loess area of Shanxi Province

a one-year experiment was carried out in the typical apple (Malus pumila)-soybean (Glycine max) intercropping system

and two factors of irrigation and fertilization were set up to analyze the influence of different water and fertilizer control measures on soil water content distribution

photosynthetic characteristics of apple and soybean

soybean growth and yield

and water use of intercropping system. In the experiment

irrigation was conducted in four key water demand periods of soybean. Fertilizer was applied with irrigation water

and different upper limit of irrigation and fertilization level were set each time. The four levels of maximum irrigation were 60% (W1)

70% (W2)

80% (W3) and 90% (W3) of field capacity (Fc)

and the three different nitrogen fertilization levels were pure nitrogen 59.40 kg/hm2(F1)

92.00 kg/hm2(F2) and 124.32 kg/hm2(F3). In addition

the rain-fed crop (neither irrigation nor fertilization during the whole growth period

only basal fertilizer was applied before sowing) was taken as the control (CK).The results indicated that the soil water content for each water and fertilizer treatment had significant differences in both horizontal and vertical directions. The influence of irrigation amount on soil water content was more significant than that of fertilization amount and interaction of water and fertilizer.The diurnal variation characteristics of net photosynthetic rate (Pn) and transpiration rate (Tr) for apple and soybean were similar

both of which were unimodal curves and the maximum values were obtained in W3F2.The plant height

stem diameter and leaf area index (LAI) of each water and fertilizer treatment for soybean increased by 1.3%~32.3%

2.8%~33.9% and 3.4%~125.9%

compared with CK

respectively. Moreover

all the maximum value of growth indexes appeared in W3F2. The soybean yield and water use efficiency (WUE) for intercropping system were also optimal in W3F2

which increased by 10.9%~99.3% and 8.0%~70.0%

compared with other treatments

respectively. The irrigation upper limit of 80% Fc could be set from sowing to emergence stage

from seedling to branching stage

from flowering to pod and blast stage. Meanwhile

92.00 kg/hm2 nitrogen fertilizer could be applied at seedling to branching stage

at pod and drum stage of soybean

respectively. This water and fertilizer management under drip irrigation could make the apple-soybean intercropping system obtain higher crop yield and water use efficiency

which could provide reference for integrated management of water and fertilizer under drip irrigation for the intercropping system in this area.