Effects of alternate wetting and drying (AWD) threshold level and plant seedling age on crop performance, water input, and water productivity of transplanted rice in Central Luzon, Philippines

Water for agriculture is increasingly becoming scarce, and the production of rice will be affected. This necessitates the development of innovative techniques that reduce water input and increase water productivity (WPI+R) of rice. Alternate wetting and drying (AWD) irrigation and use of older seedlings may help reduce the input water requirement of rice. We evaluated the effects of AWD at different threshold levels (irrigation when perched water table drops to 15, 25, or 30 cm below soil surface) in comparison with continuous flooding (CF) and of rice plant seedling ages (S) on grain yield, water input, and WPI+R of lowland rice during the 2010 and 2011 dry seasons. In both years, there was no effect of water management and a significant effect of S. 21-day-old seedlings gave the highest yields. Water savings using AWD ranged from 42.8 to 53.7 % of total water input in comparison with CF, without yield loss, but there was little difference in water input among AWD treatments. Due to shorter duration of growth in the main field, water input with 30-day-old seedlings was lower than with younger seedlings, but with a corresponding yield loss. Total water productivities in AWD treatments were higher than those with CF. Among S, 21-day-old seedlings gave the highest WPI+R and 30-day-old seedlings gave the lowest.