Field Crop 2025, Vol.8, No.3, 154-165 http://cropscipublisher.com/index.php/fc 156 2.3 Applicability and current status of regional promotion The AWD irrigation method is most suitable for rice fields with convenient irrigation and drainage and good infrastructure, where water can be flexibly controlled. However, if it is rain-fed fields that rely on the weather or low-lying and flood-prone plots, it is very difficult to implement because water cannot be drained at all. In recent years, some high-standard farmlands in southern China have been promoting the "shallow and wet alternation" model, and the agricultural department has also encouraged farmers to adopt it through training subsidies. Countries like the Philippines and Vietnam are also demonstrating and promoting this. In many places, after using it, water savings have been significant, production has not decreased, and methane emissions have been reduced by more than 30% (Chidthaisong et al., 2018). Farmers' acceptance is actually quite high, especially in areas that are often short of water or under pressure to reduce emissions (Duong et al., 2024). Nowadays, there are still some auxiliary means, such as using simple water pipe measurement or mobile phone apps to indicate the irrigation time, which is more convenient to use. In conclusion, AWD is a practical and feasible technology. However, in the initial stage of promotion, local trials should be conducted first to establish appropriate operational standards and prevent farmers from worrying about reduced yields. As conditions get better and better in the future, there will definitely be more places where it can be used (Tanaka et al., 2025). 3 The Influence of AWD on Rice Yield 3.1 Physiological and morphological mechanisms The AWD irrigation method is quite different from continuous flooding. It makes the fields sometimes dry and sometimes wet. You may know that if the soil is constantly flooded, it will lack oxygen and the roots won't grow well. However, when AWD dries up, it is actually providing oxygen to the root zone. As a result, the roots will grow deeper, distribute more, have stronger vitality and oxidation capacity, and have a wider range of nutrients to find. Moderate use of AWD can increase the root-to-crown ratio, expand the surface area of the roots, and make the absorption of nutrients such as nitrogen and phosphorus more effective (Sun et al., 2025). Moreover, the alternation of dry and wet soil can accelerate the decomposition of organic matter and release more nitrogen elements. Even a slight water pressure is not a bad thing. It will stimulate the roots to grow deeper and actually enhance the resilience. When it comes to photosynthesis, mild AWD actually has little impact on the photosynthetic rate of leaves. Sometimes, due to better ventilation and light penetration in the field, there is even a slight improvement, and both transpiration and photosynthetic efficiency can be maintained well (Yang et al., 2020). Of course, this thing should not be overdone either-if it is too dry, the stomata will close, photosynthesis will weaken, carbon assimilation will not keep up, and the yield may drop. In conclusion, AWD mainly works by improving the oxygen and nutrient conditions in the root zone, enabling roots and leaves to grow more harmoniously and achieving what is called "strong roots and thick stems". Even if water is saved, the yield can still be stable or even increased. The key is to prevent it from being too dry. 3.2 Differences in yield performance at different growth stages The impact of AWD on rice yield cannot be generalized. It depends on the type of rice and when it is used. For instance, in single-cropping rice, if a mild AWD is applied, the yield is basically not affected. The number of panicles and grains is similar to that of those that have been constantly flooded. Sometimes, the number of grains per panicle may even be a little higher-because a little drying can actually control ineffective tillering and concentrate nutrients on the longer panicles. However, if it is double-cropping rice, the situation for early rice and late rice is different: early rice has more rainfall, and appropriate drainage is actually beneficial to the growth of the group and can also maintain the yield. Late rice is prone to high temperatures and drought. If the alternations between dry and wet conditions are too frequent at this time, it may lead to insufficient tillering and less fruit production. Therefore, it is best to keep the soil moist during the panicle formation and grain filling periods. The variety is also quite crucial. For instance, many hybrid rice varieties nowadays have strong roots and are resistant to adverse conditions, so their yields remain stable under AWD conditions (Wang et al., 2024). However, some old varieties experience a significant reduction in yield as soon as there is a drought. Overall, as long as the operation is proper and the drought is not excessive during critical periods, AWD can actually achieve no
RkJQdWJsaXNoZXIy MjQ4ODYzNA==