Modeling of wheat yield and sensitivity analysis based on energy inputs for three years in Abyek town, Ghazvin, Iran

To get a proper energy consumption pattern and an increase in energy productivity, determining a relationship between energy inputs and outputs is necessary. In this study, the equivalent energy of inputs and outputs data used in wheat production in Abyek town of Ghazvin province, Iran was collected from farmers over three years. The energy ratio was obtained as 2.11, 2.08 and 2.03 and energy productivity was obtained as 0.15, 0.14 and 0.14 (kg MJ-1) for 2010, 2009 and 2008, respectively. It was found that the contributions of indirect and non-renewable energies on wheat yield were more than the impacts of direct and renewable energies. To determine the effects of energy inputs on wheat yield, the Cobb–Douglas production function was used. Model 1 was composed of individual energy inputs: labor, machinery, electricity, diesel fuel, water for irrigation, fertilizer, chemicals and seed energies In Model 2 energy inputs divided to direct and indirect energies and in Model 3 they divided to renewable and non-renewable energies. The R2 values in all three models were more than 0.98 and showed that the models can estimate well. The sensitivity analysis results for Model I showed that the major marginal physical productivities (MPPs) were water for irrigation, human labor and water for irrigation in 2010, 2009 and 2008, respectively. In Model II, the major MPP belongs to for renewable energy in the same years. Keywords: energy consumption pattern, Cobb-Dauglas, marginal physical productivity, renewable, return to scal