Cotton Genomics and Genetics 2025, Vol.16, No.2, 57-71 http://cropscipublisher.com/index.php/cgg 59 avoided in cotton planting, and soil moisture should be controlled in an appropriate range through reasonable irrigation to maintain the healthy growth of cotton (Pchelkin et al., 2023). Figure 1 Changes in the evapotranspiration components and the proportion of transpiration to evapotranspiration at different growth stages of cotton (Adopted from Zhao et al., 2023) 2.3 Effect of climate and soil conditions on water use efficiency The water use efficiency (WUE, dry matter or yield obtained per unit of water consumption) of cotton is significantly affected by the climate and soil conditions of the planting area. In an environment of high temperature, low humidity and strong radiation, the transpiration rate and evaporation loss of cotton are increased, and WUE is often lower under the same irrigation conditions; on the contrary, in a milder climate, cotton can convert more dry matter per unit of water. For example, improper irrigation in arid and hot areas such as Xinjiang and Texas will cause a large amount of water evaporation or deep seepage, resulting in low water use efficiency (Li et al., 2016; Evett et al., 2019). Soil texture and water storage capacity also affect cotton's use of water. Sandy soil has poor water storage capacity and requires more frequent irrigation, but the amount of water each time should be small, otherwise it is easy to leak and waste; clay soil has poor aeration, and excessive irrigation is prone to waterlogging (Wang et al., 2021). The degree of soil salinization is also a key factor: in saline soil, cotton needs to maintain a high irrigation leaching rate to suppress the increase in salt, but excessive irrigation will reduce WUE. Studies have shown that by optimizing irrigation scheduling, controlling soil salinity while ensuring cotton growth, efficient water use can be achieved that takes into account both water and salt. Zhang et al. (2021) found that under saline-alkali water irrigation conditions, when soil salinity is controlled within a certain threshold, cotton yield is equivalent to freshwater irrigation, thus achieving a relatively high water productivity. Therefore, when formulating a cotton irrigation system, it is necessary to consider the local climate evaporation requirements and soil characteristics, and determine the irrigation intensity and frequency according to local conditions to maximize the efficiency of cotton's use of every drop of water. 3 Classification of Cotton Irrigation Strategies 3.1 Conventional irrigation methods Before the popularization of modern water-saving technologies, conventional ground irrigation methods dominated cotton cultivation. The most traditional of these is flood irrigation (sometimes called flood irrigation), which is to flood the field at one time on flat land. This method is simple and easy to implement, but it uses a large
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