Determine of the Actual and Potential Evapotranspiration and Appropriate Model for Determining Water Requirement of Saffron (Case study: Torbat Heydarieh)

The semi-tropical plant of saffron, due to low water requirement and high income, has a special place in the cultivating pattern of arid and semi-arid regions such as Torbat Heydarieh region of Khorasan Razavi. In this research was carried out to determine the potential and actual evapotranspiration rate and the most suitable model for estimating evapotranspiration of saffron in Torbat Heydarieh (the world's saffron producing pole). The results of comparison of different methods with FAO method as standard and basic method showed that Blaney-Criddle, Genesis and Hargreaves methods were more accurately than other methods. A comparison of the results of the FAO method with other methods was performed using Chi-square test. The amount of annual water requirement of saffron in the climate of Torbat Heydarieh using the FAO method was 1731 m3 / ha. Since in the Hargreaves-Samani equation, for the calculation of evapotranspiration, only two factors are necessary for temperature and solar radiation, and it is possible to determine the factors in most weather stations, the overall result of this research is that, in the estimation of initial and Rapid need for a saffron plant in the region can be used.