determination of single and basal crop coefficients of borage medicinal plant in the region of karkaj in tabriz

for estimating plants water requirement at the different stages of plant growth, determination of crop coefficient is very important. therefore, this study was conducted to determine the crop coefficient of borage in research lands of faculty of agriculture at the university of tabriz in 2013. for this purpose, drainage lysimeter with diameter of 1.5 meter and depth of 1.7 meter was used for determining crop evapotranspiration and fao penman-montith equation was used for determining reference evapotranspiration. borage seeds were cultivated within the lysimeter with distance of 10 cm on rows and the distance between rows was 30 cm, the experiment continued for 4 months. during this period, total reference evapotranspiration and crop evapotranspiration values in the studied region were obtained as 898.8 and 812.5 mm, respectively. considering the percentage of ground cover and fao recommendation, the initial, development, middle and end stages of growth were determined as 28, 42, 20 and 14 days, respectively. the average single crop coefficients values of the initial, development, middle and end stages, were determined as 0.67, 0.97, 1.15 and 0.76, respectively and average basal crop coefficients for mentioned stages were 0.2, 0.8 1.05 and 0.65, respectively. these values of crop coefficients can be recommended for determination of water requirement and irrigation scheduling of borage.