Abstract

This paper is focused on water use aspects with the aim of: (1) calculating reference and actual evapotranspiration; (2) determining crop water requirement (CWR) and crop irrigation requirement (CIR); and (3) constructing efficient irrigation schedule (EIS) for three main crops, including winter-spring, summer-autumn, and autumn-winter using the Cropwat model based on monthly meteorological data recorded from 1984 to 2015. The results showed that winter-spring and summer-autumn harvest needed irrigation water approximately 8186 and 5830 m3/ha, respectively, while autumn-winter harvest needed approximately 2204 m3/ha. The lowest value of the reference evapotranspiration (ETc) was approximately 607.8 mm/crop occurred in autumn-winter crop, while the highest value 709.9 mm/crop occurred in summer-autumn crop. The highest IR of the winter-spring, summer-autumn crops occurred on development stage with net irrigation approximately 499.5 and 397.1 mm, respectively. While the autumn-winter crop occurred on both growth, development, and late stage with average net irrigation approximately 307 mm. The results obtained confirmed that the Cropwat model with meteorological and soil data as input variables was successfully applied to define actual evapotranspiration (ETo), ETC, CWR and EIS for three major crop seasons of rice in LXQ areas, Vietnam with reasonable accuracy.