Abstract: Sandy land in northwestern Liaoning Province is ecologically fragile. Fruit-crop intercropping can realize the win-win situation of ecological protection and economic benefits, and is widely used. We investigated the distribution of soil nutrients in four fruit-crop intercropping systems, including apple-peanut, apple-sweet potato, apple-soybean, and apple-millet, in sandy land of northwestern Liaoning Province. We analyzed the spatial distributions of soil carbon, nitrogen and phosphorus in 0-60 cm layer and 0-300 cm horizontal distance as well as economic benefits of different intercropping systems, and compared with apple monoculture and crop monocultures. In the vertical direction, soil nutrients in intercropping systems showed surface aggregation, with higher nutrient content of topsoil (0-20 cm) than that of deep soil layer (20-60 cm). In the horizontal direction, the nutrient competitive sites of apple-peanut intercropping system were evenly distributed in the horizontal range of 0-300 cm, while those of apple-sweet potato, apple-soybean, and apple-millet intercropping systems were generally located within 0-100 cm along the fruit belts. The soil nutrient comprehensive index in peanut monoculture, apple monoculture, and apple-peanut intercropping system were significantly higher than other cropping patterns. As for the nutrient effect, nitrogen showed a positive effect, while carbon and phosphorus showed a negative effect. There was an obvious nutrient competition in the apple-crop intercropping systems, and the four intercropping systems had greater demand for soil phosphorus. Among the four intercropping systems, apple-sweet potato intercropping system had the highest land equivalent ratio (LER) and income equivalent ratio (IER), apple-millet intercropping system had the lowest LER, and apple-soybean intercropping system had the lowest IER. From the perspective of land planting evaluation index, which is a comprehensive index of soil nutrient and land return, intercropping patterns perform better than monoculture, with the apple-peanut intercropping system being the best. In conclusion, the apple-peanut intercropping system is the best fruit-crop intercropping pattern in the sandy land of northwestern Liaoning Province. It is suggested to apply more organic fertilizer and phosphorus fertilizer at the nutrient competitive sites of the apple-peanut intercropping systems.

Key words: fruit-crop intercropping, soil nutrient, spatial distribution, economic benefit, sandy land in northwestern Liaoning Province