Determining potential evapotranspiration of corn by lysimetric method in Moghan

For accomplishment experiment, an arable land, that one drainage lysimeter was established in its center at last years, was appropriated for corn planting. The parameters of soil water balance equation were directly measured through drainage lysimeter, and the potential water consumption of corn was determind in 10 and 30 days interval. Also, for investigation of corn crop coefficient during growth season, another land that lysimeteric study was conducted for determination of reference evapotranspiration simultaneously, appropriated for lawn cultivating. The lawn was managed according to those recommended by F.A.O.(paper No. 13), during growthing season. The results indicated that the potentiaL water consumption of corn (average of 1379-81) in the Moghan climate condition was 901 mm from 11 Ordibehesht to 20 Shahrivar. The mean daily evapotranspiration of corn during growing season was 6.72 mm. The maximum evapotranspiration of corn occurred in first decade of Mordad, and was 9.95 mmlday. The corn crop coefficient was changed from 0.58 to 1.35. Its minimum and maximum values occurred in the second decade of Ordibehesht, and first and second decades of Mordad, respectively. Also, the product of crop and pan coefficients (KxKp) was changed from 0.41 to 0.9, that occurred in the first decade of Khordad and second decade of Tir, respectively. Also, crop coefficient of Corn had logical relation with Growth- Degree- Days (ODD). Days After Sowing (DAS), and Growth Stages (OS) indices. ODD method turned to be for predicting of corn evapotranspiration, Because of its minimum errors. Also, it was observed one Logical relation between KxKp and ODD, DAS, and OS indices. Key words: Evapotranspiration, Lysimeter, Corn, Crop Coefficient, Pan Coefficient, Growth- Degree- Days, Days After Sowing, Growth Stages