Energy use pattern and sensitivity analysis of energy inputs for saffron production in Iran

Saffron is one of the most iconic and valuable plants in Iran, with a cultivation history that spans centuries. It is a key agricultural product for export, contributing significantly to the country's foreign currency earnings. As the world's leading saffron producer, Iran accounts for 60% of global production. This study aims to analyze the patterns of energy use in saffron cultivation and explore the relationships between energy inputs and yield in the west of Isfahan province, Iran.

This research gathered the necessary data through questionnaires and interviews with saffron farmers. The inputs analyzed in the study included human labor, machinery, diesel fuel, chemical and organic fertilizers, irrigation water, electricity, and seed energy. The energy equivalent for each input was determined by multiplying the input quantities by their respective energy coefficients. Based on the energy equivalents of both inputs and outputs, key energy indices such as energy ratio (energy use efficiency), energy productivity, and specific energy were calculated. The energy ratio (energy use efficiency) was calculated using the formula: Energy Ratio = Energy Output (MJ ha⁻¹) / Energy Input (MJ ha⁻¹). To establish a mathematical relationship between energy inputs and yield, the Cobb-Douglas production function was applied. In this study, energy requirements were categorized into four groups: direct, indirect, renewable, and non-renewable. The marginal physical productivity (MPP) method was employed to analyze the sensitivity of energy inputs in saffron production. This method assesses how the performance changes when one unit of energy input is increased, while holding other production factors constant. A positive MPP value for any input suggests that increasing the input will result in higher output, implying that the input should continue to be used until the resource reaches its limit. Conversely, a negative MPP value indicates that additional units of the input decrease performance, signaling that further input use would be inefficient.

The results of this study revealed that the corm used for cultivation (seed) accounted for the highest proportion of energy consumption in saffron production, contributing 54.11%, followed by manure (13.51%) and electricity (11%). Notably, the proportion of renewable energy in saffron cultivation exceeded that of non-renewable energy consumption. Two methods were employed to calculate energy use efficiency in saffron production: one based on the total outputs, including stigma, leaf, and corm, and the other considering only the saffron stigma. For this study, the energy use efficiency was found to be 0.002 when based solely on saffron stigma. The R² value for the Cobb-Douglas production function, which was based on energy consumption, was estimated at 0.84, indicating that the model explained 84% of the variability in performance based on the five input factors: labor, irrigation water, machinery, chemical fertilizers, and animal fertilizers. The results of the Cobb-Douglas model demonstrated that the energy inputs of human labor, machinery, chemical and animal fertilizers, and irrigation water had a significant impact on yield. Furthermore, the sensitivity analysis revealed that human labor had the highest marginal physical productivity (MPP) among all input energies. With an MPP value of 0.87, human labor had the most substantial effect on saffron production, significantly influencing the overall output compared to other energy inputs.

The results of this study indicated that the total energy consumed in saffron production was 138,319 MJ/ha. Of this, renewable energy accounted for 16.46% of the total energy used. The key energy indices for saffron production were as follows: energy use efficiency was 3.7, energy productivity was 0.24 kg MJ⁻¹, specific energy was 4.8 MJ kg⁻¹, and net energy was 377,600 MJ ha⁻¹. These values provide a comprehensive overview of the energy dynamics involved in saffron cultivation, highlighting both the energy intensity and efficiency of the production process.