Agroirrigational Sedimentation and Pedogeochemical Transformation of Irrigated Oasis Soils in Uzbekistan

Introduction Long-term irrigation is a major driver of morphogenetic, agrophysical, and pedogeochemical transformation in oasis soils of arid and semi-arid regions. This study evaluated the regional variability and anthropogenic transformation of irrigated oasis soils formed under contrasting depositional, geomorphological, and hydrological conditions in Uzbekistan. Methods Serozem-oasis, serozem-meadow-oasis, and meadow-oasis soils were investigated across the Andijan, Tashkent, Sirdarya, Jizzakh, Samarkand, Kashkadarya, and Surkhandarya regions. Morphogenetic characteristics, particle-size distribution, soil reaction (pH), and total concentrations of Cu, Zn, Mn, and B were assessed. Particle-size composition was determined using the pipette method, microelements were measured by atomic absorption spectrophotometry, and regional variability was evaluated using descriptive statistics and multivariate analyses. Results Pronounced regional and soil-type differences were observed in agroirrigational horizon development, carbonate redistribution, fine sand accumulation, microelement composition, and soil reaction. Agroirrigational horizons reached up to 250 cm in intensively irrigated soils of Surkhandarya, indicating advanced anthropogenic pedogenesis. Meadow-oasis soils generally showed the highest accumulation of fine sand (0.1–0.05 mm). Mn had the highest absolute concentrations among the analyzed microelements, while Zn showed marked regional variability. Soil pH remained predominantly neutral to weakly alkaline, with mean values ranging from approximately 7.05 to 7.43. Conclusions Long-term irrigation and agroirrigational sedimentation substantially reshape the morphogenetic, physical, and geochemical properties of irrigated oasis soils in Uzbekistan. The observed regional differences reflect the combined effects of irrigation history, depositional environment, parent material, groundwater regime, and geomorphological position. These findings provide a scientific basis for long-term soil monitoring and region-specific management of irrigated agroecosystems under arid conditions.