Ralations of soil water, evapotranspiration, Growth, and water use efficiency of KMDL 105 rice (Thai)

Abstract

Evapotranspiration from rice grown under saturated soil was 4 times greater than evaporation from saturated bare soil. The rate of evapotranspiration decreased with the reduction in volumetric soil water content, and the relation could be described by an asymptotic exponential function. When soil water was expressed in terms of pF, the relation became linear. When water supply was withheld for 7 days and soil pF increased to above 4.5, rice recovered very slowly from the stress and did not attain complete recovery during the experimental period. Increase in dry weight of the stressed plants was only 30% of that of the unstressed plants, which could be contributed to the reduction in the green leaf area to only 10% of that of the unstressed plants. Water use efficiency of the stressed plants was also lower at 1.8 g DW kg-1 transpired water, than for the unstressed plants at 2.4 g DW kg-1 transpired water.