Cotton Genomics and Genetics 2025, Vol.16, No.2, 80-94 http://cropscipublisher.com/index.php/cgg 82 prominent soil degradation problems, such as decreased organic matter, nutrient imbalance, salinization, and accumulation of soil-borne diseases. In cotton-growing areas such as Xinjiang, due to years of monoculture and high chemical inputs, soil carbon and nitrogen nutrients have significantly decreased, pH and conductivity have increased, and microbial diversity has decreased. A long-term positioning study on cotton fields in Xinjiang showed that soil total nitrogen, available phosphorus, potassium and microbial biomass carbon decreased significantly after continuous cropping for more than 10 years, while salt and harmful nematodes increased significantly. The number of plant parasitic nematodes in cotton fields with continuous cropping for 25 years increased several times compared with that in fields with continuous cropping for 5 years (Chen et al., 2021). To restore soil health, rotation and fallow have been proven to be effective measures. Short-term fallow or rotation with leguminous crops can promote soil nutrient circulation and reduce continuous cropping obstacles. Chen et al. (2021) showed that the soil health index of cotton fields in Xinjiang dropped to the lowest level after about 7 years of continuous cropping, but it can be gradually restored after proper rotation. In some cotton-growing areas, promoting the "cotton-forage" or "cotton-grain crop" rotation model, rotating alfalfa or wheat every two years, can significantly improve the physical and chemical properties of cotton field soil and reduce soil-borne diseases. At the same time, attention should be paid to conservation tillage and increased application of organic fertilizers. Measures such as crushing straw and returning it to the field, planting green manure, applying compost or bio-organic fertilizer can help improve soil organic matter and microbial activity, and enhance the soil's ability to retain water and fertilizer. For example, in the organic cotton production system, the use of chemical inputs is strictly prohibited. Soil fertility and ecological balance are maintained through organic fertilization and biological control, and soil nutrient recycling is achieved (Miao and Ma, 2009). In order to reduce soil compaction and erosion, some areas adopt no-till or minimum-till technology, combined with planting cover crops to protect the surface and reduce wind erosion and water erosion. These soil health management practices not only improve soil productivity, but also enhance the cotton field's ability to resist stress such as drought, which is conducive to the long-term stability of cotton production. 2.3 Water-saving irrigation Cotton has a large demand for water, and water shortage is becoming a key factor restricting the sustainable development of cotton areas. Traditional flood irrigation methods are wasteful, often causing field runoff and deep seepage, and low water use efficiency. In arid and semi-arid cotton areas, it is imperative to promote efficient water-saving irrigation technology. Among them, drip irrigation technology is widely regarded as one of the best practices for cotton water conservation due to its precise water and fertilizer supply capabilities (Figure 1). Xinjiang, China, began to introduce Israeli drip irrigation systems in the mid-1990s, and has been rapidly promoted under the national western development policy and subsidy support. The drip irrigation area has grown from almost zero in the early 1990s to more than 3 million hectares at present, making Xinjiang the world's largest drip irrigation area and the most diverse crop types. At present, the film coverage rate of cotton fields in Xinjiang has reached 100%, and drip irrigation technology has been fully popularized, realizing precise water supply on demand. Thanks to this, despite drought and little rain, Xinjiang's cotton yield has long been among the highest in the country, and the per hectare yield has remained the highest in the country for more than 20 years (Zhao et al., 2009). Water-saving irrigation is not limited to areas with irrigation conditions such as Xinjiang. In rain-fed cotton areas such as India and West Africa, the construction of small-scale water storage and sprinkler irrigation facilities and the promotion of moisture storage and water conservation agronomy (such as mulching, deep plowing and water conservation) are also crucial to improving the efficiency of natural precipitation utilization. Studies have shown that precision irrigation can save a lot of water while ensuring yield. A study based on meta-analysis summarized the results of many trials of drip irrigation cotton in Xinjiang and found that compared with full irrigation, moderate deficit irrigation treatment increased water use efficiency by an average of 7.39%, and only reduced seed cotton yield by about 15%. When the deficit irrigation ratio is within 90%, the yield decrease is very small, and the water efficiency is significantly improved (Xu et al., 2024). Therefore, through precise irrigation scheduling, appropriate control of irrigation volume in the late growth period can achieve "significant water saving with slight reduction in yield". In addition, the application of "soil measurement-moisture content-weather" digital monitoring combined with intelligent irrigation system makes on-demand irrigation possible. For example,
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