Under water shortage conditions, the farmers are faced with risk and uncertainty in decision making. The main objectives of this study are to selecting the well-managed deficit irrigation, the optimum plant density and appropriate planting method in order to decrease the sugar beet yield risk and water consumption risk. The gross margin (GM) and economic water productivity (EWP) are two main economic criteria, which are affected by yield and water consumption; therefore, they can be considered as risky parameters. This study uses Stochastic Dominance with Respect to a Function (SDRF) and stoplight graphs to evaluate the GM and EWP in three levels of irrigation regimes (100% (II), 75% (I2), and 50% (I3) of full irrigation), four plant densities (180,000 (P1), 135,000 (P2), 90,000 (P3), and 45,000 (P4) plants ha−1) and two planting methods (direct seeding (D) and transplanting (T)) in sugar beet cultivation experiment, conducted in a split-split plot arrangement. The results from the SDRF method for GM and EWP analysis show that for lower risk aversion farmers, the I2 irrigation level and for upper-risk aversion farmers, the I1 irrigation level are the most preferred options. However, for both upper and lower risk aversion farmers, the P3 plant density and transplanting method are the most preferred options. By considering the interaction effects of irrigation regimes, plant densities, and planting methods on EWP, the I2P3T treatment is the most preferred treatment followed by I2P2T and I3P3T for both lower and upper-risk aversion farmers based on the SDRF method. The results showed that by using the deficit irrigation strategy in the same level of probability, the higher GM and EWP can be achieved as compared to the full irrigation strategy. The stoplights graph also indicated that the irrigation level of I2, plant density of P3, and transplanting method can increase the value of EWP to a higher level as compared to other treatments. Therefore, under condition of water deficit, combining these treatments can be helpful for obtaining the optimum GM and EWP in sugar beet cultivation.
Irrigated sugar beet (Beta vulgaris) has been produced in last one century in Iran. Nowadays, about 32% of sugar supply is obtained from sugar beet, (Draycott, 2006), which is usually cultivated under arid and semi-arid environments. In 2018, approximately 2 million tons of sugar beet were produced in Iran from a total irrigated area of 23,000 ha (Zamani et al., 2019). The Iranian government has persuaded the farmers to produce sugar beet by a guaranteed price due to the fact that the farmer decision-making is related to gross margin (GM) achieved from sugar beet cultivation. Obtaining certain GM is not possible for farmers, because GM is related to the risky variables such as yield and production costs. While most farmers tend to be risk averse, attitude concerning risk is not fxed. Degree of risk aversion is deferred for farmers so risk management is an important process.
Conclusion and Recommendation
The main objective of this study is to investigate the efect of diferent irrigation regimes, various plant densities as well as the direct seeding and transplanting method on GM and EWP with considering the risk analysis due to the fact that the farmer’s decision making in many times is under uncertainty and risky conditions. Regarding the present study, the risk attitude was considered for economic objectives in order to manage the suitable production of sugar beet cultivation.
The experimental results showed that the two-year average values of the maximum root yield and gross margin were obtained from treatment I1 and decreased by about 9% and 28% by decreasing the irrigation water from I1 to I2 and I1 to I3, respectively. The maximum values of root yield and gross margin were obtained from treatment P3 and decreased by either increasing or decreasing plant density. The transplanting method resulted in saving irrigation water, in average for two years, by about 19.5%, while decreasing the gross margin by about 4%. Decreasing the gross margin in the transplanting method is due to the higher production costs in this method as compared to the direct seeding method.