Introduction: There is a close relationship between population growth and rapid economic development and overuse of natural resources. Recently, one of the main problems of human societies is the management of energy consumption. In agricultural ecosystems, there is a strong dependence on non-free inputs and free environmental inputs. In different production systems, different methods are used to increase stability. Various methods have been utilized to investigate the sustainability of agricultural systems such as emergy analysis. Emergy analysis is an ecological approach that measures all the inputs from natural resources and human activities that are directly and indirectly used to obtain a particular product. This method estimates all the resources, including energy, consumed environmental resources, and financial and human costs based on solar energy units. By considering both economic and ecological factors, emergy analysis helps identify ways to achieve maximum crop yield while supporting resource efficiency in agricultural production. Emergy analysis is a method used for sustainability assessment of agroecosystems, including potato production. It determines the most important indicators related to efficiency, renewability, environmental pressure, and sustainability of potato agroecosystems. Although the sustainable production of crops has been analyzed by some researchers, the effects of farm size have not been considered so far. Hence, in the current study, the effect of farm size on sustainability of potato production was studied using the emergy methodology.
Materials and Methods: In order to evaluate the effect of farm size on the sustainability of potato production, a study using emergy analysis was conducted in Fariman county in 2018-19. Information was collected in different potato production systems in terms of farm size including small, medium and large (Based on Cochran's formula, 30, 15 and 5 farms respectively) using questionnaires completed by farmers. The inputs were divided into four types to examine the sustainability of agroecosystems and calculate the emergy indices: Free renewable environmental inputs (R) include sun, wind and rain; non-renewable environmental inputs (N) include groundwater, soil erosion, and soil organic matter losses; non-free (purchased) renewable inputs (FR) include seeds and organic fertilizer; and purchased non-renewable inputs (FN) include machinery, chemical fertilizer, pesticides, fuel, and electricity. To obtain the emergy value of each input, the raw information of each input is multiplied by the conversion coefficients in terms of joules, grams, or Rials. The total emergy is the sum of all emergies of all independent inputs. Finally, emergy indices are calculated and interpreted to evaluate different production systems.
Results and Discussion: The results of this research showed that different potato production systems have different effects on the contribution of different sources of total energy. By increasing the size of the farm, the share of renewable natural resources decreased and the share of purchased resources increased. Among the renewable environmental inputs in all three emergency systems, rain had the highest amount. The amount of renewable environmental inputs for production systems in small, medium and large farms was 1.42, 1.13 and 1.04% of the total inputs, respectively. Cultivation in small farms required the least amount of emergy for crop production in contrast to large farms. In addition, cultivation on large farms was more similar to cultivation on medium farms in terms of purchased resources. On the other hand, large farms had high sustainability compared to small farms based on the ELR index. In addition, large farms were not significantly different from medium farms. Since the economic yield of large farms was much higher than the economic yield of medium and small farms, other indicators of emergy except renewable energy were also higher in large farms than in medium and small farms.
Conclusion: In this area, cultivation in large fields with the use of more mechanization has improved the yield along with maintaining the stability of the production system.