Estimation of sugar beet irrigation requirement in different regions of Fars province in critical conditions and definite probability levels

Irrigation requirement equals the difference between water requirement and effective rainfall which can be estimated by considering the water application efficiency. The values of water requirement and irrigation requirement of sugar beet have been reported using NETWAT program in different regions of Iran. However, the mean values were used in this program; therefore the values of water and irrigation requirements have the probability level of 50 percent. In the current study, the values of sugar beet irrigation requirement in the probability levels of 10, 20, 30, 40, 50, 60, 70, 80 and 90 percentage and critical conditions (high evapotranspiration and low rainfall) were determined in some regions of Fars province such as Abadeh, Eghlid, Darab, Dorodzan Dam, Zarghan, Shiraz and Fasa by using long- term weather data. The results showed that the critical irrigation requirement of sugarbeet was equal to its irrigation requirement in the probability level of 90 percent, and the reported values of sugar beet irrigation requirement by NETWAT program were equal to 92 percent of its critical irrigation requirement, in Fars province. Also, it is possible to estimate sugar beet irrigation requirement in different probability levels and critical condition by using the obtained regression equations in Fars province.