Rice Genomics and Genetics 2025, Vol.16, No.5, 254-259 http://cropscipublisher.com/index.php/rgg 255 2 AWD Irrigation Technology: Principles and Implementation 2.1 Definition and water depth control methods Alternate wetting and drying (AWD) is an irrigation practice designed to reduce water usage in rice cultivation by allowing the soil to dry out to a certain extent before re-irrigation. This method contrasts with continuous flooding, where fields are kept submerged throughout the growing season. AWD involves monitoring the water depth and allowing it to drop below the soil surface to a predetermined level before reapplying water. The water depth control is crucial, as it determines the frequency and amount of irrigation needed. For instance, in some studies, water levels are allowed to drop 10, 20, or 30 cm below the ground before re-irrigation. The optimal water potential for AWD is often maintained at pressures greater than -15 kPa, with water depths less than 18.5 cm during the rice growing season (Figure 1) (Zhang et al., 2023). Figure 1 Alternate wetting and drying irrigation (AWD) (Adopted from Zhang et al., 2023) 2.2 Implementation requirements and field infrastructure Implementing AWD requires specific field infrastructure and management practices. Fields must be equipped with tools to measure water depth accurately, such as field water tubes or simple observation wells. These tools help farmers determine when to irrigate based on the water level. Additionally, the field must be leveled properly to ensure uniform water distribution and prevent waterlogging in certain areas. The infrastructure should also support efficient water delivery and drainage systems to facilitate the alternate wetting and drying cycles (Gilardi et al., 2023; Wijesundara, 2024). In regions with shallow aquifers, the interaction between irrigation and groundwater recharge must be considered to maintain overall irrigation efficiency (Gilardi et al., 2023). 2.3 Irrigation scheduling across rice growth stages AWD irrigation scheduling is tailored to the different growth stages of rice, ensuring that water is applied when it is most needed. During the early stages of rice growth, fields may be kept flooded to suppress weeds and support seedling establishment. As the rice plants mature, the AWD method is employed, allowing the soil to dry to the specified depth before re-irrigation. This cycle is repeated throughout the growing season, with adjustments made based on weather conditions, soil type, and crop needs (Carrijo et al., 2017; Cheng et al., 2022). The scheduling must be flexible to accommodate variations in environmental conditions and to optimize water use efficiency without compromising yield (Gao et al., 2024). 3 Case Study Region and Field Application 3.1 Xinghua, Jiangsu—AWD in a rice-wheat rotation system In Xinghua, Jiangsu, the application of alternate wetting and drying (AWD) irrigation in a rice-wheat rotation system has shown promising results. The AWD technique is particularly beneficial in regions with water scarcity, as it reduces water consumption while maintaining rice yields. Studies have demonstrated that AWD can decrease water use by 25%-70% compared to traditional continuous flooding methods, without significantly impacting rice
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