Abstract: We examined the distribution characteristics of soil nutrients and microbial biomass in fruit-crop intercropping system (apple (Malus pumila)soybean (Glycine max)) in a sandy land of northwestern Liaoning. Soil nutrients and microbial biomass in the 0-60 cm soil layer and the horizontal distance of 0-300 cm in the intercropping system were measured, and further compared with that in soybean monoculture and apple monoculture. The results showed that soil nutrient was poor in the apple-soybean intercropping system, with total nitrogen, available nitrogen and available phosphorus being extremely deficient. Horizontally, with the increases of the distance from apple trees, the concentrations of soil organic matter, available nitrogen, total phosphorus and available phosphorus in the intercropping system were decreased first, then increased, and eventually tended to be stable. The nutrient competitive area was located at the fruit tree belt \[0, 100 cm). At the vertical direction, all types of nutrients in the apple soybean intercropping system exhibited surface aggregation, with nutrients content in topsoil (0-20 cm) being significantly higher than that in deep soil (20-60 cm). Soil microbial biomass carbon and nitrogen and the quantity of bacteria were high in fruit tree belt and topsoil. There were significant differences of nutrient contents between intercropping and monoculture in topsoil, with the differences being narrowed with the deepening of soil layer. Except the alkaline hydrolysis nitrogen, the effects of intercropping system on soil nutrients were negative, which could not meet the requirement of intercropping system. The requirement of the intercropping system for soil nitrogen and phosphorus was substantial. In conclusion, there was an obvious competitive relationship in the apple-soybean intercropping system, especially in the fruit tree belt. The application of nitrogen and phosphate fertilizers in the intercropping system should be strengthened.

Key words: apple-soybean intercropping, soil nutrient, soil microbial biomass, sandy land, spatial distribution.