Comparative evaluation of different methods to compute evapotranspiration at different phenological stages in wheat

Abstract

Evapotranspiration of wheat crop was estimated using different methods viz. lysimeter, USDA Open pan evaporimeter, empirical methods, combination approach and soil water evaporation model. The field experiment was conducted during rabi 2006-07 and 2007-08 with two weighing type lysimeters located at the research farm, Punjab Agricultural University, Ludhiana. Among different methods of ET estimation, Papadakis method computed highest rate of PET followed by Hamon and modified Penman method whereas modified soil evaporation model, Thornthwaite, Blaney-Criddle and Stephans & Stewart methods produced lower values of PET as compared to lysimeter ET and open pan evaporation. Modified Jensen & Haise method estimated PET values (346 and 361 mm) closest to lysimeter ET (340 and 341 mm) and open pan evaporation (360 and 432 mm) respectively, for two seasons. PET computed by Blaney-Criddle method showed very good correlation with Lysimeter ET (0.90).

Keywords

• Evapotranspiration
• wheat
• vapour pressure deficit
• lysimeter
• empirical methods
• crop coefficient