Quantification of the water exchange in an agroforestry system under the background of film-mulching drip irrigation of farmland

Abstract

Water availability is the most critical constraint for the healthy and sustainable development of agroforestry systems in arid and semi-arid regions; consequently, it is essential to clarify soil water dynamics and quantify water exchange within agroforestry systems. In this study, a two-year field experiment and a HYDRUS-2D numerical simulation model were used to clarify the characteristics of the two-dimensional distribution of soil water and the horizontal water exchange in an agroforestry system under the background of film-mulching drip irrigation of farmland. The results showed that the HYDRUS-2D for agroforestry systems had high accuracy in calculating the water flow and capturing the dynamic water exchange in various soil layers. The model simulation results showed that there were differences in soil water content between forest belt and farmland, and the two-dimensional distribution of soil water content showed vertical water transport and horizontal water exchange in the agroforestry system. During the growing season, the horizontal water flow exchange was mainly from the forest belt side and the farmland side to the agroforestry transition zone, with inflows of 61.3 mm and 199 mm at depths of 0–100 cm, respectively. A long-term severe "water stress zone" developed at a depth of about 0–40 cm in the forest belt, so the 0–40 cm soil depth was the main area of water competition in the agroforestry system. The results could provide a reference for the long-term healthy development of agroforestry systems and the management of agricultural water resources in oasis-desert systems under film-mulching drip irrigation conditions.