Optimum allocation of salt discharge areas in land consolidation for irrigation districts by SahysMod

Soil salinization seriously threats the sustainability of agriculture in irrigation districts in arid and semi-arid regions. Unreasonable land consolidation aimed to increase cultivated land by developing uncultivated land makes soil salinization more serious in irrigation districts in the northwest of China. The uncultivated land serves as the salt discharge area, which is necessary for cultivated land with reasonable area, excavation depth, and spatial allocation. Therefore, this study aims to optimize the allocation of salt discharge areas based on soil water and salt movements simulated by SahysMod, choosing Yinchuan North Irrigation District as a case study in the northwest of China. Results showed that SahysMod was an effective tool to simulate soil water and salt movements between cultivated land and salt discharge areas. The parameters of optimum allocations, including excavation depths of salt discharge areas and area ratios of cultivated land to salt discharge areas, indicated the negative and positive effects of power functions on soil salinity of cultivated land, respectively. In this case study, an excavation depth of 0.3 m, the area ratio of 1.5, and salt discharge areas located in the southwest and northeast were more conducive and cost effective in terms of removing soil salinity of cultivated land. Moreover, the average soil salinity of cultivated land by optimum allocation was reduced to 1.2 dS/m compared with 2.7 dS/m by original allocation in 2027. It proved that the reasonable allocation of salt discharge areas was very important to address soil salinization of cultivated land and ensure its sustainable utilization, which provided a theoretical basis and technical guide for the allocation of salt discharge areas in land consolidation in the arid irrigation districts.