Bittawat Wichaidist, Amornrat Intrman, Pavit Junhom, Songsak Puttrawutichai, Chawakorn Rewtragulpaibul, Chaisri Suksaroj
Efficient water management is crucial for modern rice cultivation, particularly in the context of climate change and limited water resources. To optimize irrigation, this study evaluated the physiological responses of rice to water stress. From January to April 2022, a randomized complete block design (RCBD) was employed to evaluate physiological traits associated with water regulation in rice plants. Key photosynthetic metrics, including stomatal conductance (g sw ), leaf temperature (T leaf ), fluorescence (F s ), electron transport rate (ETR), and photosystem II efficiency (Φ PSII ), as well as stress markers such as malondialdehyde (MDA) content and osmolality, were monitored. Results showed that g sw shifts preceded visible stress symptoms, making them reliable early indicators of irrigation need. In the second experiment, water-use efficiency, plant stress, and greenhouse gas (GHG) emissions were measured from October 2022 to February 2023 to refine alternative wetting and drying (AWD) methods for better water-use efficiency. Using g sw thresholds, the modified AWD (mAWD) outperformed conventional AWD (cAWD) in terms of irrigation water productivity (WP I ) and consumptive water footprint (WF consumption ) without inducing stress conditions in rice. WP I for continuous flooding (CF), cAWD, mAWD was 1.16, 2.72 and 3.92 kg m −3 , while WF consumption was 1,079.93, 584.90 and 517.57 m 3 t −1 , respectively. Additionally, mAWD reduced yield-scaled GHG emissions, enhancing environmental benefits. This study underscores the value of physiological monitoring, especially g sw , to advance AWD irrigation for sustainable rice production.