Estimation of Water Requirement and Crop Coefficient for Hemp at Different Growth Stages in Birjand Plain

Determination of crop water requirement is of great importance in irrigation planning and effective management of water in agriculture. In this regard, lysimeters are used to measure water input and output and water balance method. Therefore, this research was carried out to determine the water requirement of Cannabis sativa L. in 2017 at the Faculty of Agriculture of Birjand University. For this purpose, six weighing lysimeters were used and cannabis water requirement was calculated using the water balance equation. Three lysimeters were planted to grass (12 cm height) as the reference crop, and in the other three lysimeters the cannabis plant was cultivated. Based on the results of the water balance equation, the evapotranspiration potentials of the reference plant and cannabis were 899.6 and 688.89 mm, respectively. The length of different stages of plant growth, including the initial, development, middle and end stages, was 30, 55, 75, and 20 days, respectively. Also, the cannabis crop coefficient values in the four stages of plant growth were 0.28, 0.68, 1.01 and 0.54, respectively. These values are recommended for estimating the water requirement and irrigation management of cannabis.