coriandrum sativum l. crop coefficient determination in a semi-arid climate

coriandrum sativum l. is one of the most important plants compared to the other herbs and medicinal plants as a planted covered area in kermanshah province. for a suitable irrigation management programming, the awareness of crop coefficient and water requirement in different plant stages is essential. the ratio of actual evapotranspiration to reference crop evapotranspiration is defined as crop coefficient. a study was conducted to determine the crop coefficients of (coriandrum sativum l.) in faculty of agriculture research farm in razi university in kermanshah city during 2009-10 and 2010-11. for this purpose, three water balance drainable lysimeters with diameter of 1.20 m and a height of 1.40 m were used. in this regard, to calculate potential evapotranspiration, the penman monteith equation for potential evapotranspiration and water balance equation to measure actual evapotranspiration were used. finally, the values of crop coefficients for different (coriandrum sativum l.) initial, development, middle and end stages were determined as 0.66, 1.19, 1.36 and 0.98, respectively.