Field evapotranspiration characteristics and water use efficiency of aerobic rice under different water treatments

Four years’ experiments (2001-2004) were conducted in Beijing from 2001 to 2004 to study the characteristics of crop evapotranspiration (ET), soil evaporation, and water use efficiency (WUE) of aerobic rice under four different water conditions. Crop evapotranspiration was calculated from the soil water balance equation, and soil evaporation was measured by micro-lysimeter in the field. Results showed that the total ET during the whole growing season of aerobic rice in Beijing varied between 574 and 630 mm among years. The highest daily ET occurred at the stage from booting to heading stage with the average value of 9.8 mm/d. Therefore, booting to heading is the key stage of water requirement for aerobic rice. More than 40% of the total ET was consumed during the period from emergence to jointing, however, most of this part of ET was used for soil evaporation. Therefore, it is necessary for efficient water use to take some measures to reduce the consumption of soil evaporation at this stage. Comparing among water treatments, WUE was the highest in the treatment with limited irrigation before jointing but sufficient irrigation thereafter.