Litter decomposition is important for understanding the effects of habitat on nutrient cycling. In this study, we investigated the decomposition characteristics, decomposition variability, and regulatory factors restricting the decomposition rates of leaf litter in three different habitats: a flood disturbance habitat, an arid habitat, and a high-salinity habitat. The litter decomposition rates of the habitats decreased in the following order: flood disturbance habit > arid habitat > high-salinity habitat. The organic carbon, total nitrogen, and lignin residues of the litter during the decomposition period were highest in the high-salinity habitat. The litter quality was the main regulator of the release of phosphorus and cellulose residues, which exhibited different release processes and patterns in these three habitats. The litter decomposition coefficient was negatively correlated with litter carbon residue in the flood disturbance habitats, the lignocellulose index in the arid habitats, and soil urease in the high-salinity habitats. It was positively correlated with the lignocellulose index in flood disturbance habitats and litter carbon residue in high-salinity habitats. The litter quality in the flood disturbance area played a significant role in litter decomposition, while environmental quality and litter quality were the dominant factors under arid and high-salt conditions. Litter quality in the flood disturbance area played a significant role in litter decomposition, while both environmental quality and litter quality were the dominant factors under arid and salt conditions.

Water and nitrogen (N) are the most critical limiting factors for sudangrass (Sorghum sudanense (Piper) Stapf) growth under drip irrigation in arid oases of southern Xinjiang, yet the quantitative interaction mechanism governing yield–quality–efficiency trade-offs remains unclear. This study employed a quadratic orthogonal regression design to generate 11 water–nitrogen treatment combinations (irrigation: 1800–4200 m³·ha⁻¹; nitrogen: 240–720 kg·ha⁻¹). Agronomic traits, dry matter yield, nutritional quality, and nitrogen use efficiency (NUE) were measured through field experiments in 2023–2024, and quadratic models were fitted to identify optimal water–nitrogen bundles maximizing multi-objective performance. Irrigation volume was the dominant factor controlling the plant height, SPAD index, and stem–leaf ratio, whereas stem diameter depended on the water × N interaction (p < 0.01). The “medium-water × moderate-nitrogen” regime (3000 m³·ha⁻¹ + 480 kg·ha⁻¹) maximized dry matter yield (~28 t·ha⁻¹), NUE (~44%) and forage quality (Relative Feed Value > 135, crude protein ≥ 8.8%). This climate-adaptive precision strategy reduces water use by 30% and nitrogen by 20% while increasing yield by 15% and quality by 15%, providing a sustainable production framework for arid and semi-arid regions of Xinjiang.