Abstract

Alternate Wet and Dry Irrigation (AWDI) is a water management system where rice fields are not kept continuously submerged but are allowed to dry intermittently during the rice growing stage. A field experiment was conducted in Chiba, Japan during the rice growing season (May-September) of 2008 to assess AWDI and continuous submerged water management practices for their effects on productivity, the surrounding environment, water savings, and Water Productivity Index (WPI). The impact of age of seedlings and plant spacing were also assessed.

AWDI using the proposed irrigation schedule of 10 wet days alternated with 10 dry days used less water (29% less water) without significant reduction in grain yield (7.2 t/h) compared with conventional irrigation (7.8 t/h). Water Productivity Index was significantly higher in all sub-plots in AWDI treatments. WPI was 1.7 kg/m³ in AWDI treatments compared to 1.3 kg/m³ in conventional water management. Additional significant results from AWDI treatment included reduced pest and disease incidence, shortened crop cycle, and reduced lodging. However, slightly higher grain yields were observed in all sub-plots of the conventional irrigation treatment than were observed in the same combinations under AWDI. This underscores the need for further research in defining what constitutes an optimum interval for AWDI considering local soil properties, prevailing climate, and the critical periods during the rice growth cycle when the yield was particularly sensitive to moisture stress.

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