Impact of Deficit Drip Irrigation with Brackish Water on Soil Water-Salt Dynamics and Maize Yield in Film-Mulched Fields

Maize production in the arid and semi-arid regions of northwest China is limited by water scarcity, while the abundance of brackish water highlights the opportunity for its effective and sustainable utilization. A 2-year field experiment (2022-2023) was conducted in the Shiyang River Basin to investigate the impacts of deficit irrigation with brackish water on soil moisture, salinity, temperature, crop growth index, yield, and water productivity. Six treatments were implemented, consisting of two irrigation levels (W1: 75%I, W2: 100%I) and three water quality gradients (S0: 0.7 g L-1, S1: 3.7 g L-1, S2: 5.7 g L-1 in 2022 and 7.7 g L-1 in 2023). Results indicated that brackish irrigation (except S0) increased soil salinity, keeping the soil water storage at higher levels, while decreased maize yield, and water productivity (WP). Compared with full irrigation at the same salinity level, deficit irrigation decreased soil salinity, keeping the soil water storage at lower levels, while increasing soil temperature, which led to lower maize yield but resulted in higher WP. Path analysis of soil hydrothermal salinity and crop growth indicators demonstrated that soil salinity changes play a crucial role in determining maize plant height and yield. S0W2 (100% irrigation, 0.7 g L-1) achieved the highest maize yield, with S0W1 yielding 5.15% less. However, the water productivity (WP) of S0W1 was 17.66% higher than that of S0W2. Therefore, considering the combined factors of maize yield, water productivity, and water-saving benefits, the use of S0W1 (75% irrigation, 0.7 g L-1) is recommended.