Determination of Evapotranspiration and Crop Coefficient of Saffron (Crocus sativus L.) by Lysimetric Method in the Dry- Desert Climate of Birjand

Saffron is herbaceous, perennial and semi tropical plant belongs to Iridaceae family that cultivated in Southern Khorasan province as an importance crop. Considering the importance of irrigation water content in saffron yield, this research was conducted to determine the water requirement of saffron in a research farm of the Faculty of Agriculture, University of Birjand in the crop year 2018-2019. Six mini lysimeter were used to carry out this research. Three lysimeter were used to calculate the evapotranspiration of the reference plant (grass) and in the other lysimeter saffron cultivate. Irrigation of each experimental unit was carried out based on field capacity by weight method. Based on the results obtained from the water balance equation, the potential evapotranspiration of the reference plant and saffron values were estimated 1138.81 and 764.12 mm, respectively. The length of various growth stages of saffron, including the initial, developmental, middle and end stages, was 30, 50, 55 and 65 days, respectively. Finally, based on the FAO method, the coefficient of variation was plotted and the average crop coefficient at four stages of plant growth was 0.48, 0.84, 1.27 and 0.37, respectively. Also, the effects of four- stages of plant growth on potential evapotranspiration of the reference plant, saffron and crop coefficient were significantly different at 1% level.