In light of the shortage of water resources and the lower fertility and poor quality of soils in Xinjiang, this study explored the effects of varying irrigation volumes and ratios of organic to inorganic fertilizer application under aerated drip irrigation on the soil quality, cotton growth, yield, and water use efficiency of cotton fields. The objective was to provide a theoretical basis for determining an irrigation and fertilization model for cotton in Xinjiang that was water-saving, highly efficient, and sustainable.

Field experiments were conducted in the 146th Regiment area of the Xinjiang Production and Construction Corps in 2023 and 2024. Under aerated drip irrigation, two irrigation volumes (W1: 80%ET_C and W2: 100%ET_C, where ET_C represents the crop evapotranspiration) and five ratios of organic to inorganic fertilizer application (OF1: 100% chemical fertilizer, OF2: 75% chemical fertilizer + 25% organic fertilizer, OF3: 50% chemical fertilizer + 50% organic fertilizer, OF4: 25% chemical fertilizer + 75% organic fertilizer, OF5: 100% organic fertilizer) were set up to study their impacts on the physical and chemical properties of soil quality, cotton growth including leaf area index (LAI), dry matter accumulation, yield, and water use efficiency (WUE).

The Soil Quality Index (SQI) increased with the rising proportion of organic fertilizer, showing an average increase of 9.9%-28.8% in the combined application of organic and inorganic fertilizers over the two years compared with the application of chemical fertilizer alone. Under deficit irrigation, soil moisture content, LAI, dry matter accumulation, and yield significantly decreased, while Water Use Efficiency (WUE) significantly increased. Under the two irrigation levels (W1 and W2), soil moisture content, cotton LAI, and dry matter accumulation first increased and then decreased as the proportion of organic fertilizer increased. Under W1, these indicators reached their maxima with the W1OF3 treatment, whereas under W2, their maxima were observed with the W2OF2 treatment. Compared with chemical fertilizer alone (OF1), the combined application of organic and inorganic fertilizers increased soil moisture content, LAI, and dry matter accumulation by 0.4%-5.2%, 4.1%-19.8%, and 3.7%-18.8% over two years, respectively. Over two years, the maximum seed cotton yield was observed under W2OF2 treatment, with an average yield of 6739.99 kg·hm^-2, but the highest WUE was achieved under the W1OF3 treatment, with an average value of 1.42 kg·m^-3. The SQI, seed cotton yield, and WUE under different treatments were evaluated using the membership function method, TOPSIS method, and grey relational analysis, respectively. A comprehensive evaluation was carried out using an integrated differential combination evaluation model, determining the optimum treatment as W1OF3.

Considering the priority of water-saving, while ensuring yield, and aiming to improve Water Use Efficiency (WUE) and soil quality, it was recommended that under aerated drip irrigation, applying 80% ET_C for irrigation water volume and a combined application of 50% organic fertilizer and 50% chemical fertilizer, for serving as the optimal management measure for water-saving and efficient production in cotton fields in Xinjiang.

The objective of this study is to investigate the effect of water and nitrogen coupling on tomato yield and water use efficiency (WUE) under aerated drip irrigation, and to provide a scientific basis for water and nitrogen management for tomato cultivation in Northwest China.

Two greenhouse experiments were carried out in 2023 and 2024, and three irrigation levels W1 (50% ET_C), W2 (75% ET_C) and W3 (100% ET_C) were set under aerated drip irrigation with micro and nano bubble generating devices (ET_C is the actual crop evaptranspiration). Three nitrogen application levels were N1 (0), N2 (150 kg·hm^-2) and N3 (250 kg·hm^-2), and W3 (100% ET_C) N3 (250 kg·hm^-2) under traditional drip irrigation was used as control treatment (CK). The effects on soil moisture content, hydraulic characteristics, photosynthetic characteristics and yield of tomato were studied.

Aerated drip irrigation promoted the uptake and utilization of soil water in tomato, improved plant hydraulic characteristics and leaf photosynthetic characteristics, and increased yield and WUE by 1.21% to 1.84% and 1.84% to 2.25%, respectively. Optimized water and nitrogen management under aerated drip irrigation could further promote tomato growth and yield. Soil moisture content increased with increasing irrigation but decreased with increasing nitrogen application, reaching a maximum in the W3N1 treatment, which was 0.31% to 19.37% higher than other treatments; tomato stem water potential, Pn, Gs, and SPAD all increased with increasing irrigation and nitrogen application, reaching maximum values in the W3N3 and W2N3 treatments, respectively, and increasing by 0.95% to 104.86% compared with other treatments. PLC decreased with the increase of irrigation water and N application and decreased to the minimum value in W3N3 treatment, which was 11.27% to 69.24% lower than other treatments. Nitrogen application under deficit irrigation alleviated water stress in tomato plants, and soil moisture content, stem water potential, PLC, Pn, Gs and SPAD were significantly improved by 17.37% to 21.16% under deficit irrigation W2 compared with W1. Yields of both spring-summer and autumn-winter tomato reached the maximum in the W2N3 treatment, WUE reached the maximum in the W2N3 and W1N3 treatments, respectively, and autumn-winter tomato WUE was increased by 1.02% in the W1N3 treatment compared with W2N3, but yield was significantly decreased by 15.25%. Path analysis revealed that the direct effect coefficient of soil moisture content on yield under aerated drip irrigation was 0.439, while the indirect effect coefficients of soil moisture content on yield through stem water potential, PLC, Pn and Gs were 0.952, 0.852, 0.582 and 0.494, respectively.

Nitrogen application under aerated drip irrigation can improve the hydraulic characteristics of tomato under different irrigation conditions, enhance the photosynthetic capacity of leaves, and then improve the tomato yield. Considering the yield and WUE, the appropriate irrigation volume and nitrogen application rate for tomato in Northwest China are 75% ET_C and 250 kg·hm^-2, respectively.