Field Crop 2024, Vol.7, No.4, 232-242 http://cropscipublisher.com/index.php/fc 234 reducing greenhouse gas emissions. The field tube, partially submerged in the soil, allows farmers to monitor the water table and decide when to irrigate. When the water table drops 10-15 cm below the soil surface, irrigation is needed. This method optimizes water usage while preventing stress from drought, ensuring that rice yields remain stable. AWD is widely implemented in Asian countries, proving effective in conserving resources while maintaining productivity. Figure 1 Perforated plastic field tube to examine the below-ground water table in AWD (Adopted from Mallareddy et al., 2023) 3.2 Historical development of AWD The development of AWD as a water-saving technique has been driven by the need to address water scarcity and reduce the environmental impact of rice cultivation. Initially, AWD was introduced as a response to the high water demand and greenhouse gas emissions associated with CF systems. Over the past two decades, AWD has gained traction in various rice-producing regions, including the Philippines, Thailand, and Malaysia, due to its potential to conserve water and mitigate methane emissions (Sriphirom et al., 2019; Ishfaq et al., 2020; Enriquez et al., 2021). In the Philippines, for example, AWD has been scaled up through national policy adoption, supported by local adaptations and innovations (Enriquez et al., 2021). 3.3 Comparison with traditional methods Compared to the traditional CF method, AWD offers several advantages. It significantly reduces water usage, with studies reporting water savings ranging from 25% to 70% (Mubeen and Jabran, 2019; Sriphirom et al., 2019; Ishfaq et al., 2020). Additionally, AWD has been shown to decrease methane emissions by 11% to 95%, depending on the specific implementation and environmental conditions (Sriphirom et al., 2019; Ishfaq et al., 2020; Malumpong et al., 2020). While CF systems are known for their high water consumption and associated environmental issues, AWD provides a more sustainable alternative by improving water use efficiency and reducing the accumulation of harmful substances like arsenic and mercury in rice grains (Mubeen and Jabran, 2019; Ishfaq et al., 2020; Monaco et al., 2021). However, the effectiveness of AWD can vary based on factors such as soil type, weather conditions, and the degree of dryness allowed between wetting cycles. For instance, incomplete AWD, where the drying phase is interrupted by rainfall, may not achieve the same benefits as complete AWD, particularly in terms of yield and greenhouse gas emissions (Sriphirom et al., 2019). Despite these challenges, AWD has been successfully implemented in various regions, demonstrating its potential as a viable alternative to traditional rice cultivation methods (Mubeen and Jabran, 2019; Sriphirom et al., 2019; Ishfaq et al., 2020; Enriquez et al., 2021). In summary, AWD represents a significant innovation in water management for rice cultivation, offering substantial benefits in terms of water conservation, environmental sustainability, and potentially improved grain quality. Its adoption and adaptation continue to evolve, driven by the need to address the challenges of water scarcity and climate change in rice-producing regions worldwide.
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