Cotton Genomics and Genetics 2025, Vol.16, No.2, 57-71 http://cropscipublisher.com/index.php/cgg 60 amount of water and has uneven water distribution, which can lead to local overwetting and deep leakage. Another common method is furrow irrigation, which is to dig ditches to divert water along the ridges to flood and infiltrate the cotton rows. This method has better water flow control than flood irrigation, relatively uniform irrigation in the field, and reduces surface runoff losses. Therefore, traditional cotton fields mostly use furrow irrigation. However, conventional ground irrigation is inefficient, with the water use efficiency of SF irrigation being only 57%. Other studies report that the efficiency of flood irrigation is even between 35% and 44% (Singh et al., 2022). Ground irrigation was widely used in cotton fields when water resources were abundant or water prices were low in the past. However, in the current context of water shortage, its disadvantages of high water consumption and low efficiency are prominent. Excessive surface irrigation can also cause the movement and accumulation of soil salts and nutrient loss, which is not conducive to the long-term health of the soil environment. Despite this, in some areas where farmland infrastructure is poor or pressurized water delivery equipment cannot be used, conventional flooding and furrow irrigation are still the irrigation methods followed by cotton farmers, and field engineering improvements and scientific guidance are needed to improve their water use efficiency (Sajid et al., 2020). 3.2 Advanced irrigation technology In order to improve the efficiency of cotton irrigation water use, various efficient and water-saving irrigation technologies have been developed and applied. Among them, drip irrigation is one of the fastest-growing technologies in cotton in recent years. Drip irrigation uses drip irrigation pipes laid on the surface or underground to directly provide water to the vicinity of the cotton root zone in a low-flow, frequent and small-dose manner. In Xinjiang and other places, sub-film drip irrigation is widely used, that is, drip irrigation belts are buried under the ridges covered with plastic film to achieve the dual effects of reducing surface evaporation and precise water and fertilizer supply. Drip irrigation technology can increase the efficiency of irrigation water use to about 90% and significantly increase cotton yield. Studies have shown that compared with traditional furrow irrigation, drip irrigation can save 30%-50% of water and increase seed cotton yield by 10%-20% (Ayer et al., 1984). Another advanced technology is sprinkler irrigation, which uses sprinklers to simulate rainfall for irrigation. It is widely used in cotton-growing areas such as the United States and Australia. Sprinkler irrigation can moisten the soil more evenly and is suitable for large-scale mechanization, but evaporation losses are relatively high in windy and dry areas. In recent years, a new type of subsurface drip irrigation has also begun to be used for cotton, that is, burying drip irrigation pipes deeper underground to further reduce evaporation losses and promote root penetration. Some innovations, such as introducing air into the drip irrigation system to form oxygenated drip irrigation to improve oxygen supply in the root zone (Pendergast et al., 2013), or integrated water and fertilizer irrigation combined with nutrient delivery, are also being tested in cotton fields (Nie et al., 2021). Overall, advanced irrigation technology has achieved a higher output-input ratio for cotton by more accurately distributing water. For example, in an IoT-controlled smart drip irrigation experiment, cotton yield increased by nearly 67% and water consumption decreased by about 12% compared with manual empirical irrigation (Guo and Chen, 2024). The promotion of these technologies provides important support for the development of cotton production towards high yield, high efficiency, water conservation and environmental protection. 3.3 Deficit and precision irrigation methods Under conditions of limited water resources, deficit irrigation strategies are often adopted, that is, planned reduction of irrigation water supply within the crop tolerance range to save water. For cotton, moderate deficit irrigation can reduce irrigation volume without significantly reducing yield, thereby improving water production efficiency (Xu et al., 2024). Guirguis et al. (2015) showed that reducing irrigation volume by 10% during the entire growth period of cotton has little effect on yield, but can save about 15.2% of water and increase water use efficiency by 7%. In particular, if water deficit occurs in a growth stage where cotton has strong tolerance (such as the end of the vegetative growth period), the plant can minimize the impact through physiological adaptation (Ullah et al., 2017). In field trials, a mild deficit treatment of 90% full irrigation not only met the water needs of cotton but also avoided over-irrigation, showing a yield equivalent to full irrigation and significant water-saving effect (Xu et al., 2024). In order to achieve more sophisticated water management, the concept of precision
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