The mulch film residues in cotton fields in south Xinjiang have caused serious harm to the soil environment and ecological security in the oasis areas. Non-mulched planting provides an alternative approach to this problem. In this experiment, irrigation was provided on the basis of the reference crop evapotranspiration (ET₀). Two layouts of drip tapes (1T4R—one tape for four rows; 2T4R—two tapes for four rows) were applied to the non-mulched, drip-irrigated cotton fields in south Xinjiang, and their impacts on soil water–heat–salt dynamic changes and the water consumption and yield of cotton were compared and analyzed. The experiment shows that the 2T4R layout provided an excellent soil water–salt environment for cotton growth and yield formation. Soil temperature decreased by 0.8 °C and drip irrigation belt input increased by CNY1200·hm⁻². However, a higher profit derived from the 2T4R layout could compensate for the increased expenditure. The results show that cotton cultivation using non-mulched drip irrigation instead of mulched drip irrigation can potentially alleviate soil environmental and ecological security problems caused by plastic mulch residues in oasis areas. Although cotton yield was reduced by about 15%, water and nitrogen strategies and other field management could be adjusted to compensate for the disadvantages.

Low temperature and soil salinization during cotton sowing and seedling adversely affect cotton productivity. Exogenous melatonin (MT) can alleviate the damage caused to plants under non-biological stress; thus, applying MT is a means to improve the growth condition of crops under stress. However, achieving this goal requires a thorough understanding of the physiological regulatory mechanisms of MT on cotton seedlings under low temperature and salinity stress. This study could bring new knowledge on physio-biochemical mechanisms that improve the tolerance of cotton seedlings to combined effects of low temperature and salt stress using an exogenous foliar application of MT. The phytotron experiment comprised two temperature levels of cold stress and control and five MT treatments of 0, 50, 100, 150, and 200 μM and two salinity levels of 0 and 150 mM NaCl. Compared with the control treatments (non-salinity stress under cold stress and control), the combined stress of salt and low temperature reduced cotton seedlings’ biomass and net photosynthetic rate (P_n), aggravated the membrane damage, reduced the potassium (K⁺) content, and increased the sodium (Na⁺) accumulation in the leaves and roots. Under NaCl stress, exogenously sprayed 50–150 μM MT increased the biomass and gas exchange parameters of cotton seedlings under salt and low temperature combined with salt stress, reduced the degree of membrane damage, and regulated the antioxidant enzyme, ion homeostasis, transport, and absorption of cotton seedlings. The pairwise correlation analysis of each parameter using MT shows that the parameters with higher correlation with MT at cold stress are mainly malondialdehyde (MDA), peroxidase (POD), and catalase (CAT). The highest correlation coefficient at 25 °C is observed between the K⁺ and Na⁺ content in cotton seedlings. The conclusion indicates that under salt and low-temperature stress conditions, exogenous application of MT primarily regulates the levels of P_n, superoxide dismutase (SOD), andPOD in cotton seedlings, reduces Na⁺ and MDA content, alleviates damage to cotton seedlings. Moreover, the most significant effect was observed when an exogenous application of 50–150 μM of MT was administered under these conditions. The current study’s findings could serve as a scientific foundation for salinity and low-temperature stress alleviation during the seedling stage of cotton growth.

Crop coefficients are critical to developing irrigation scheduling and improving agricultural water management in farmland ecosystems. Interest in dwarf cultivation with high density (DCHD) for apple production increases in Aksu oasis, southern Xinjiang. The lack of micro-irrigation scheduling limits apple yield and water productivity of the DCHD-cultivated orchard. A two-year experiment with the DCHD-cultivated apple (Malus × domestica ‘Royal Gala’) orchard was conducted to determine crop coefficients and evapotranspiration (ET_a) with the SIMDualKc model, and to investigate apple yield and water productivity (WP) in response to different irrigation scheduling. The five levels of irrigation rate were designed as W1 of 13.5 mm, W2 of 18.0 mm, W3 of 22.5 mm, W4 of 27.0 mm, and W5 of 31.5 mm. The mean value of basal crop coefficient (K_cb) at the initial-, mid-, and late-season was 1.00, 1.30, and 0.89, respectively. The Kc-local (ET_a/ET₀) range for apple orchard with DCHD was 1.11–1.20, 1.33–1.43, and 1.09–1.22 at the initial, middle, and late season, respectively. ET_a of apple orchard in this study ranged between 415.55–989.71 mm, and soil evaporation accounted for 13.85–29.97% of ET_a. Relationships between total irrigation amount and apple yield and WP were developed, and W3 was suggested as an optimum irrigation schedule with an average apple yield of 30,540.8 kg/ha and WP of 4.45 kg/m³ in 2019–2020. The results have implications in developing irrigation schedules and improving water management for apple production in arid regions.