Field Crop 2024, Vol.7, No.4, 232-242 http://cropscipublisher.com/index.php/fc 233 This study comprehensively evaluates the benefits and challenges associated with the Alternate Wetting and Drying (AWD) technique in rice cultivation. Its specific objectives encompass assessing the technique's impact on water usage and water productivity, evaluating its effects on rice yields and yield components, analyzing its environmental benefits particularly in reducing greenhouse gas emissions, and identifying the optimal conditions for AWD's effectiveness as well as the potential barriers to its widespread adoption. By synthesizing findings from multiple studies, this study endeavors to offer a holistic perspective on the potential of AWD to enhance the sustainability of rice cultivation practices. 2 Traditional Water Management Practices in Rice Cultivation 2.1 Continuous flooding method The continuous flooding (CF) method is a traditional water management practice in rice cultivation where rice paddies are kept submerged under water throughout most of the growing season. This method ensures that the rice plants have a constant supply of water, which is crucial for their growth and development. CF is widely used because it helps control weeds, pests, and diseases, and maintains soil temperature, which is beneficial for rice growth (Ishfaq et al., 2020; Subedi and Poudel, 2021). However, this method requires a significant amount of water, making it less sustainable in regions facing water scarcity (He et al., 2020; Kwanyuen et al., 2021). 2.2 Limitations and challenges Despite its widespread use, the continuous flooding method has several limitations and challenges. One of the primary issues is the high water requirement, which is becoming increasingly unsustainable due to global water scarcity and competition for water resources from other sectors (Kwanyuen et al., 2021; Subedi and Poudel, 2021). Additionally, CF can lead to the accumulation of heavy metals such as arsenic and mercury in rice grains, posing health risks to consumers (Ishfaq et al., 2020). The method also contributes to the decline in soil health, including reduced soil organic matter and increased micronutrient deficiencies, which threaten the long-term sustainability of rice production (Livsey et al., 2019; Ishfaq et al., 2020). 2.3 Environmental impact The environmental impact of the continuous flooding method is significant. CF is a major contributor to greenhouse gas (GHG) emissions, particularly methane (CH4), which is released from the anaerobic decomposition of organic matter in flooded rice paddies (Jiang et al., 2019; Sriphirom et al., 2019). Methane is a potent greenhouse gas, and its emission from rice fields contributes to global warming. Additionally, CF can lead to water pollution due to the runoff of fertilizers and pesticides, which can contaminate nearby water bodies (Gonçalves et al., 2022). The method also results in high water consumption, which can deplete local water resources and affect the availability of water for other uses (Maneepitak et al., 2019; He et al., 2020). In summary, while the continuous flooding method has been a reliable practice for rice cultivation, its high water demand, negative impact on soil health, and significant environmental footprint highlight the need for more sustainable water management practices in rice farming. 3 Alternating Wetting and Drying (AWD): An Overview 3.1 Definition and process of AWD Alternating Wetting and Drying (AWD) is a water management technique used in rice cultivation that involves the periodic drying and re-watering of rice fields. This method contrasts with the traditional continuous flooding (CF) system, where fields are kept submerged throughout the growing season. In AWD, the water level is allowed to drop to a certain threshold, typically 15 cm below the soil surface, before re-watering to a depth of about 5 cm (Figure 1). This cycle is repeated throughout the growing period, except during the flowering stage when a shallow water depth is maintained to ensure optimal grain filling (Mubeen and Jabran, 2019; Ishfaq et al., 2020; Enriquez et al., 2021). Mallareddy et al. (2023) illustrates a perforated plastic field tube used in Alternate Wetting and Drying (AWD) irrigation for rice cultivation. AWD, developed by the International Rice Research Institute (IRRI), is a water-saving technique that alternates between flooding and drying phases, enhancing water-use efficiency and
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