Abstract:

【Objective】 The quantification of transpiration and evaporation in an oasis field in the middlestream of the Heihe River basin in Northwest China was studied in order to provide a basis for laying down a reasonable crop irrigation system and improving the utilization efficiency of regional water resources. 【Method】 Based on the microclimatic and other supplementary experimentation data of maize field in Linze Inland River Basin Research Station, China Ecosystem Research Network, four different Penman-Monteith equations with two time-steps suggested by FAO-56 and ASCE were applied to calculate reference evapotranspiration (ET0) over a maize field in 2009, then FAO-56 dual crop coefficient method was applied to calculate canopy transpiration and soil evaporation over the same field in 2009. 【Result】 The actual evapotranspiration (ETc) for the FAO-56-PM 24h, ASCE-PM 24h, FAO-56-PM 1h, ASCE-PM 1h with dual crop coefficient methods totaled 672.1 mm, 766.2 mm, 991.2 mm and 805.6 mm, respectively. 【Conclusion】 Compared with the eddy covariance data and measured evaporation data by micro-lysimeter, the FAO-56-PM 24h equation can well estimate ET0, and can provide a fairly good estimation of ETc with dual crop coefficient. The total evapotranspiration of the maize field in 2009 was 671.2 mm, with the mean daily value of 4.1 mm. The cumulative amount of transpiration and evaporation were 498.5mm and 172.7 mm, accounting for 74.2% and 25.8% of the total evapotranspiration during the maize growing season, respectively.

Key words: Penman-Monteith equation, dual crop coefficient, transpiration, evaporation