Two-Source Energy Balance Model (TSEB) Evaluation for Evapotranspiration Partitioning of Corn under Drip Irrigation in Farm Scale

The accurate separation of evapotranspiration components is one of the key gaps in evapotranspiration research. Knowing this variable as well as the mechanism of separating its components to determine the exact value of the components of the water balance equation in relation to planning and managing water resources, optimizing crop production, designing irrigation systems, evaluating crop performance, identifying plant stresses and the impact of drought, and also evaluating the effects of climate change is very important on the efficiency of water consumption. In this research, the efficiency of Two-Source Energy Balance (TSEB) model was evaluated to separate the components of this parameter. In this regard, the outputs of TSEB model were compared and evaluated with the outputs of the standard FAO-56 dual crop coefficient method in the corn field located in the agricultural research station of Ferdowsi University of Mashhad. For this purpose, four Landsat 8 satellite images were used between planting and harvesting corn plants in the spring and summer planting seasons of 2021. The results of this research showed that despite the closeness of two methods (TSEB and FAO-56 dual crop coefficient method with R2=0.94) in terms of total values of evapotranspiration, there is a big difference between the two methods in terms of detail components (R2=0.46 for transpiration and R2=0.75 for evaporation). This difference can be due to the overestimation of the transpiration amount and underestimation of the evaporation amount in the dual crop coefficient method, and because the FAO-56 dual crop coefficient method estimates transpiration and evaporation values and it can be associated with some error, it cannot be said for sure that the TSEB model is not accurate enough. Also, comparing the ratio of transpiration to evapotranspiration in this research (0.77) with the results of other researchers (0.75-0.88) showed that the outputs of the TSEB model are within the permissible range and provide reliable outputs.