Simulation of Saline Water Irrigation for Seed Maize in Arid Northwest China Based on SWAP Model

Water resource shortages restrict the economic and societal development of China’s arid northwest. Drawing on groundwater resources for irrigation, field experiments growing seed maize (Zea mays L.) were conducted in 2013 and 2014 in the region’s Shiyang River Basin. The Soil–Water–Atmosphere–Plant (SWAP) model simulated soil water content, salinity, and water–salt transport, along with seed maize yield, in close agreement with measured values after calibration and validation. The model could accordingly serve to simulate different saline water irrigation scenarios for maize production in the study area. Waters with a salinity exceeding 6.0 mg/cm3 were not suitable for irrigation, whereas those between 3.0 and 5.0 mg/cm3 could be acceptable over a short period of time. Brackish water (0.71–2.0 mg/cm3) could be used with few restrictions. Long-term (five years) simulation of irrigation with saline water (3.0–5.0 mg/cm3) showed soil salinity to increase by over 9.5 mg/cm3 compared to initial levels, while seed maize yield declined by 25.0% compared with irrigation with brackish water (0.71 mg/cm3). An irrigation water salinity of 3.0–5.0 mg/cm3 was, therefore, not suitable for long-term irrigation in the study area. This study addressed significance issues related to saline water irrigation and serves as a guide for future agricultural production practices.