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Capillary water, serving as a crucial intermediary between groundwater and crop root layer moisture, is important for both soil retention and crop utilization. To investigate the effect of mulched drip irrigation (MDI) on upward capillary water in cotton fields with different application years (0, 10, 14, 18, 20, and 24 years) in the saline–sodic region of Northwest China, an indoor soil column test (one-dimensional capillary water rise experiment) was conducted. The results showed that the wetting front transport law, capillary water recharge, and wetting front transport rate over time exhibited an increasing trend in the early stages of MDI application (10 and 14 years), peaking at 18 years of application, followed by a decreasing trend. The relationship between the capillary water recharge and rising height was fitted based on the Green–Ampt model, and their slopes reveal that 14 and 18 years of MDI application required the largest amount of water per unit distance, indicating an excellent water-holding capacity beneficial for plant growth. Conversely, 0 years required the smallest amount of water per unit distance. Based on the movement characteristics of upper capillary water, we confirmed that the MDI application years (0–18 years) improves soil infiltration capacity, while the long-term application years (18–24 years) reduces groundwater replenishment to the soil. Furthermore, the HYDRUS-1D model was employed to simulate the capillary water rise process and soil moisture distribution under different MDl application years. The results showed an excellent consistency with the soil column experiments, confirming the accuracy of HYDRUS-1D in simulating the capillary water dynamics in saline–sodic areas. The results would provide suggestions to achieve the sustainable development of long-term drip-irrigated cotton fields. [ABSTRACT FROM AUTHOR]

The evaluation of soil particle composition and salt dynamics is essential for promoting the sustainable development of oasis agriculture in arid regions under long-term mulched drip irrigation (MDI). In this study, we employed the space-for-time substitution method to investigate the long-term effects of MDI on soil particle composition and salinity. Additionally, seven fields, with MDI durations ranging from 0 to 16 years, were selected to represent the primary successional sequence though time in Northwest China. Soil samples were collected from three soil depths (0–30 cm, 30–60 cm, and 60–100 cm) and then analyzed in the laboratory for soil particle composition and salt content. Our findings demonstrated that influenced by the depth of mechanical cultivation and the maximum wetting front depth, the long-term application of MDI significantly altered both the structure of soil layers and the composition of soil particles after 8 years. Soil sand content and soil salinity gradually decreased, whereas the content of soil silt and clay increased with increasing MDI duration throughout 0–100 cm soil depth. Furthermore, the rates of soil desalination stabilized after 10 years of MDI application, with desalination levels exceeding 90% in the 0–100 cm soil layer. Additionally, the soil mass fractal dimension (Dm) exhibited an upward trend across 0–100 cm soil depth. The changes in soil particle composition indirectly influenced the variations in Dm and salt content. Our study demonstrated that long-term application of MDI effectively mitigated soil salinity, changed soil structure, and ultimately enhanced soil quality and cotton yield. [ABSTRACT FROM AUTHOR]