International Journal of Plant & Soil Science

The accurate estimation on crop evapotranspiration (ETc) and crop coefficients is of assistance infield proper irrigation and water management. In present study, experiments were carried through out two years (i.e., 2012 and 2013) to determine water requirements (single and dual crop coefficients of basil) by using a few drainable lysimeters in a semi-arid region in Iran. Three lysimeters were used for grass evapotranspiration while three others were used to estimate bare soil evapotranspiration. Also, basil seeds were planted in six lysimeters and two groups, including group A where plant grew continually until the end of flowering stage, and group B where the plant was harvested three times after it reached a height of 0.25-0.30 m. The average water requirements of basil in two lysimeters including groups A and B were determined to be 636.8and 849mm, respectively. Finally, single and base crop coefficients for lysimeters in group A for the initial development and middle stages of basil growth were determined to be as 0.71, 1.11, 1.39and 0.57, 0.97, 1.26, respectively. Moreover, SIMDualKc, a soil water balance and irrigation scheduling model, was developed by using dual crop coefficient approach for ETc estimation. The model was calibrated and validated by comparing the measured and simulated Dual Kc values for basil for a semi-arid climate. The results indicated with low RMSE and MBE and highR²=0.83,the model was capable of accurate in proper irrigation, planning and scheduling in semi-arid climates.