Assessing evapotranspiration rate and sesame (Sesamum indicum) crop water use under different water table depths

Abstract

This research was intended to determine the groundwater contribution in crop water-use of sesame crop under different water tables depths and to assess the accuracy of CROPWAT model to simulate the evapotranspiration. The method of combining Lysimeters was implemented to investigate seasonal groundwater contribution to crop-water use. The climatic conditions under which crop was grown were monitored, water table depths were maintained (at 1.60 m, 2.0 m and 2.40 m) and all water balance components were measured. The crop coefficient (K_c), ET and reference evapotranspiration (ET_o) were determined. The obtained results were compared with the outputs of the CROPWAT model. The results reveals that, the average ET of sesame crop under lysimeter experiment was about 450 mm which was slightly increased under increased water table depths. Around 40% of groundwater contribution was recorded in overall crop-water use. The crop coefficient values were exceeded above 1.0 due to high foliage, developed through better canopy cover. The average water use efficiency was observed as 21 kg/m³. The predictions of CROPWAT model were virtually same as observed in the lysimeter experiment. The total ET was predicted as 434 mm, the predicted crop coefficient were ranging from 0.38 to 0.98. The soil moisture balance predicted by the model reveals the same trend of soil moisture balance as observed in the field. The predicted irrigation schedule was also resembling the same trend of irrigation applications as observed under lysimeter experiment. Thus, the utilization of CROPWAT model is durably suggested to be used as management tool to overcome the salinity and waterlogging problems caused by over irrigation events.