Determination of Evapotranspiration for Wheat by Using Bowen Ratio Energy Balance Method

The actual evapotranspiration of rainfed wheat was determined by using Bowen ratio energy balance and water balance methods under Cukurova region conditions. The seasonal evapotranspiration of rainfed wheat was 477 and 494 mm for BREB and water budget methods, respectively. The seasonal evapotranspiration of wheat under irrigated conditions was calculated as 708 mm by using water budget method. A linear correlation (R-2 = 0.83) was found between the evapotranspiration obtained by water budget and Bowen Ratio energy balance methods. The single crop coefficients (Kc) for wheat were determined by using the FAO Penman-Monteith equation. The seasonal Kc values were calculated as 0.55, 0.98, 1.47 and 0.77 for initial, crop development, mid-season and maturity periods, respectively. The grain yield was 661 and 551 kg.da(-1); the biomass was 1611 and 1645 kg.da(-1) under rainfed and irrigated conditions, respectively. The biomass water use efficiency (WUEb) was 3.38 and 3.45 g.m(-2).mm(-1) whereas grain yield water use efficiency (WUEy) was 1.39 and 1.15 g.m(-2).mm(-1) for rainfed and irrigated conditions, respectively. Harvest index (HI) was 0.44 and 0.34 for rainfed and irrigated conditions, respectively. On the basis of the rainfed and irrigated conditions, there were no significant differences between grain yield and biomass values according to the variance analysis.