Growing Season Evapotranspiration and Crop Coefficient

by Esmaiel Malek,
Gail E. Bingham,



Document Type: Proceeding Paper

Part of: Management of Irrigation and Drainage Systems: Integrated Perspectives

Abstract:

The Bowen ratio-energy balance (BREB) method was used to continuously estimate 20-minute actual evapotranspiration (ET_a) in the middle of a 36-ha well-watered alfalfa field from 10 April to 5 October, 1992. Daily totals of ET_a were compared with potential evapotranspiration (ET_p) estimated using the modified Penman method. About 90% net radiation (R_n) was utilized for ET_a, and the crop coefficient K_c = ET_a/ET_p was 79%. The crop coefficient occasionally was greater than unity. Regression analysis revealed that R_n = 0.560R_s - 1.317 with r = 0.933 and R_n = 0.556R_s - 0.830 with r = 0.959 for clear and clear-plus-cloudy sky conditions, respectively, during the season where solar radiation (R_s) and R_n are in MJ m^-2. This BREB method is a promising tool for automated irrigation systems in remote areas.

Subject Headings: Evapotranspiration | Crops | Solar radiation | Regression analysis | Irrigation systems | Vegetation | Seasonal variations

Services: Buy this book/Buy this article

 

Return to search