Soil Moisture and Soil Nutrient Content in Walnut-Crop Intercropping Systems in the Loess Plateau of China

Abstract

Agroforestry has been widely applied in the Loess Plateau of China as a means of reducing soil and water losses, restoring ecological balance, and improving both land-use efficiency and economic returns. However, agroforestry also introduces a degree of competition for soil moisture and nutrients. Walnut (Juglans regia L.)–peanut (Arachis hypogaea L.) and walnut–soybean (Glycine max L. Merr.) intercropping systems that have been used throughout the Loess Plateau were selected as the basis for a study of agroforestry system—its advantages and its disadvantages with respect to soil moisture, soil nutrients, root distributions, yields, and economic returns. The results showed that soil moisture and nutrient levels were affected by intercropping with walnut trees, and that the degree to which they were affected decreased as distance from the trees increased. On the other hand, intercropping with walnut trees can increase land-use efficiency by 75% and economic returns by 17%. On the basis of the study findings, we conclude that walnut–peanut and walnut–soybean intercropping can be practical and beneficial in the study region, but irrigation and fertilization methods need to be further studied and improved, root barriers should be installed at the tree-crop interface, and the distance between crops and tree rows should be adjusted to minimize competition for soil moisture and nutrients.