Seasonal weather effects on crop evapotranspiration and rice yield

C. S. Chan and A. W. Cheong

Abstract

Studies on the crop water requirement over different seasons, seeding rates and the comparison of estimation methods against field measurement showed that there is no significant effect of seeding rate on vapotranspiration (ET). Lower seeding rates were compensated upon crop establishment with more tillers. The average value of ET/Epan ratio was 1.56 throughout crop growth in the main season and 1.75 during the off-season. The ET value differed between rice varieties and was distinctly higher in the off-season. Estimation methods such as Jensen-Haise and Hargreaves Radiation are not quite useful for reliable measurement of actual field ET and neither is the simulation model Cropwat 7.0. The yield of direct seeded crop is generally lower in the off-season, so is the transplanted crop. Crop establishment by direct seeding is more productive than by transplanting in the main season.

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