بوم شناسی کشاورزی (Nov 2021)
Sustainability Assessment of Six Crop Production Systems based on Emergy and Economic Analysis in Hirmand City
Abstract
IntroductionNatural scientists and agricultural experts are aimed to provide the right methods of ecosystem design in order to promoting the health of natural systems, optimizing input consumption, enhancing production per unit input consumption, improving economic efficiency and increasing ecological sustainability. To achieve these goals, it is necessary to assess the sustainability of the agroecosystem to identify challenges and strengths. Quantification of sustainability leads to an increase in awareness of the state of the system, which is of particular importance in making the right decisions and managing them. Emergy is a thermodynamic tool for assessing the sustainability of biological and agricultural systems. By evaluating and comparing the sustainability of production systems in this way, human activity in the ecosystem is translated into the language of thermodynamics. Over the past three decades, emergy as a powerful tool has been prove to examine the overall performance and sustainability of the different production systems. The use of emergy analysis approach in assessing the sustainability of crop systems, leads to the application of proper management to increase the sustainability of production in these systems. In this study, six production systems of wheat, onion, garlic, fennel, cumin and black seed were evaluated in the city of Helmand, Iran, using ecological and economic indicators in terms of ecological sustainability.Materials and MethodsThis study was conducted in the production systems of wheat, onion, garlic, cumin, fennel, and black seed in Hirmand County in 2019 and 2020. For this purpose, 117 farms were selected for wheat, 47 farms for onions, 32 farms for garlic, 17 farms for cumin, 12 farms for fennel and 8 farms for black seed. Information on inputs and outputs of crop systems were obtained using the following two methods: first, verbal estimates using a questionnaire, and second, field measurements and researchers' observations. In this study, free renewable and non-renewable environmental inputs and non-free inputs for two systems were determined in terms of the same unit of solar emjoule (sej). To analyze production systems and calculate the indices, inputs were categorized into four types; free renewable environmental inputs (R), free non-renewable environmental inputs (N), free renewable inputs (FR) and non-free non-renewable inputs (FN). The emergy-based indices calculated in this study were Transformity (Tr), Renewable emergy percentage (%R), Emergy Yield Ratio (EYR), Emergy Investment Ratio (EIR), Emergy Exchange Ratio (EER), Environmental Loading Ratio (ELR), Emergy Sustainability Index (ESI), and Emergy Index of Product Safety (EIPS).Results and Discussion Total emergy supporting for the production systems of wheat, onion, garlic, fennel, cumin and black seed in Hirmand County were 3.25E+16, 3.37E+16, 4.36E+16, 2.29E+16, 1.84E+16, and 1.82E+16 sej ha-1, respectively. Free environmental flows represented 74.27, 67.85, 52.21, 56.16, 56.56 and 52.49% of the total input energy of the production systems of wheat, onion, garlic, fennel, cumin and black seed, respectively. The large share of free internal inputs indicated that most of the studied farms are non-industrial systems that are traditionally managed and low-input. The values calculated for the sustainability indices (ESI and ESI*) showed that the ecological sustainability of the fennel production system is higher than the other systems. The main reason for the greater sustainability of this system was the high share of energy input related to free environmental inputs and economic renewable resources. In addition, high emergy exchange ratio (EER), environmental sustainability resulting from the impact on the market, less emergy expended in the production of each unit of production and higher productivity of all production factors indicated a greater comparative advantage of the fennel production system.Conclusion Overall, assessments based on the calculation of 14 emergy and economic indicators showed that special attention to practical solutions for the overall management of production ecosystems, in particular the protection of the soil organic matter and preventing soil erosion can increase the ecological sustainability in the main agricultural systems of Hirmand County.
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