Two-Week Mid-Season Drainage with Alternate Irrigation Enhances Yield and Water Use Efficiency in Environmentally Friendly Rice Cultivation

This study evaluated the growth characteristics and yield of rice under various water management strategies in an environmentally friendly paddy field in Korea from 2022 to 2024. The water management treatments included mid-season drainage (MD) lasting for 2, 3, or 4 weeks, followed by either low-level water management (maintaining a 4 cm water depth, denoted as “1”) or alternate wetting and drying irrigation (4 cm irrigation followed by drying, denoted as “2”) until harvest. The conventional treatment consisted of continuous flooding (CF). Treatments with poor yields (4MD1 and 4MD2) were discontinued in subsequent years. The rice cultivar Saecheongmu was transplanted in June, and water management began in July. Among the treatments, CF produced the highest number of mean panicles, whereas the 2MD2 treatment showed the most favorable yield components. The highest mean grain yield was recorded in 2MD2, with values of 5.85, 5.74-, and 5.38-tons ha−1 over the three years—representing a 7.8–15.0% increase compared to CF. Across all treatments, MD1 consistently produced higher yields than MD2. Water use was lowest in 2MD2, achieving a 61.8% reduction compared to CF. Overall, the 2MD2 treatment emerged as the most promising strategy, effectively reducing water use by 61.8% while maintaining high yields comparable to those under continuous flooding.