Effects of Thinning Density on Soil Water Content of Alfalfa and David Peach Intercropping in the Hilly Loess Plateau, China

Intercropping alfalfa (Medicago sativa) between the four meters inter-row spacing of David peach (Amygdalus davidiana) is one of replantation practices at the Longtan catchment in Gansu province of the western Loess Plateau in the early 1980’s. However, both alfalfa and David peach are deep-rooted species and their intercropping results in excessive consumption of soil water in the hilly Loess Plateau. To alleviate this, we set up four density/intercrop treatments, which includes: David peach+alfalfa (PA), David peach (P), 60% David peach+alfalfa (60% P+A) and 60% David peach (60% P). TRIME was used to quantify the soil water content in 0 to 180cm soil layers. We found that the deep layer (120-180 cm) soil water content of PA treatment was only 6.9%-8.7% during the growing season, which was close to the permanent withering point (6.5%). The soil water storage of shallow layer (0-60 cm) under P treatment was higher than the other three treatments during the dry season (April-June). Compared with the PA, the soil water storage of deep layer under the 60% P treatment increased by an average of 5.7%. This study concluded that the intercropping of alfalfa and David peach intensified the deep soil water deficit and reducing the vegetation density may be a good measure for the restoration of soil water.