Efficient irrigation management is crucial for maintaining soil fertility and reducing secondary salinization in arid regions irrigated with mineralized water. This study evaluated the effects of soil-moisture-based deficit irrigation on the agrochemical properties and salt distribution of moderately saline meadow-alluvial soils under cotton (Gossypium hirsutum L., cv. Chimboy-5018) during 2016-2018. Six treatments were established by combining three water-supply levels (≈40%, 60% and 80%) with two pre-irrigation moisture thresholds (70-70-60% and 80-80-60% HB). Soil samples from 0-30, 30-50 and 50-100 cm layers were analyzed for humus, total NPK, mobile NO₃-N, P₂O₅, K₂O, and water-soluble salts. Total NPK contents showed little variation among treatments, whereas mobile nutrient forms displayed pronounced vertical redistribution depending on the irrigation regime. Lower water supply (≈40%) resulted in nutrient accumulation in the topsoil together with increased concentrations of Na⁺ and Mg²⁺ salts. Higher irrigation levels (≈80%) enhanced leaching, reducing salt accumulation in the root zone but also decreasing available K₂O by 35-45%. The intermediate 60% regime provided the most balanced conditions, maintaining moderate salt leaching, stable nutrient distribution, and the lowest risk of secondary salinization. ANOVA revealed significant differences in cotton yield, with the highest yield (30.4 c/ha) obtained under the 80% water-supply regime, while the 60% regime demonstrated comparable productivity with lower water use. Overall, moderate deficit irrigation (≈60%) represents the optimal strategy for sustaining soil quality and crop productivity under saline irrigation conditions in arid environments.