Investigation the Effects of Climate Variables on Yield and Yield Risk of Dry-land Wheat Using Moment-Based Models

The yield of agricultural products and their risk are highly conditional on climate conditions. Thus, investigating how these changes will affect yields of different crops and their risk of production is of interest to producers and agricultural policy makers. This study tries to investigate consequences of changes in climate parameters on yield and risk of dry-land wheat production in Mashhad city. To this end, annual time series data on dry-land wheat yield and monthly climate information over 1991 to 2017 in Mashhad were used to specify crop yield conditional probability distribution functions, using Moment-based regression models. Unconditional yield distribution then, was derived using the yield conditional probability distributions. Finally, simulation approach was used to simulate the effects of changes in the climate parameters on the mean and variance of yield distribution. Results reveal that the rainfall factor in the vegetative growth phase and in the germination stage, the total annual precipitation, and the numbers of days that go below zero degree of Celsius in the sleep stage are important factors in determining the yield and yield risk of dry-land wheat in Mashhad. The simulation results indicate that the yield’s mean of dry-land wheat will fluctuate between +21.40% and -20.49% relative to the base line yield, given the best or the worst reviewed climate condition is prevailed. In addition, given the upward trend of average annual temperature and downward trend of total annual precipitation during the past 26 years in Mashhad, and according to IPCC climate change prediction, an increase in the risk of production and a decrease in the mean of the yield is expected in the future. Accordingly, developing an appropriate variety which is dry resistance, or searching for an appropriate plant to be substituted for the dry-land wheat in Mashhad can be suggested as a way to face with climate change challenges in this region.