عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Humans need to expend energy to meet their basic food. Excessive fossil energy makes it possible to provide food to the growing population. While, population is increasing, energy resources (especially fossil fuels) are declining, so communities need basic planning for energy management. Agricultural activities are among that energy consuming needs. By consuming energy inputs, the crops are produced. Besides, water is the other key input. Use of fossil fuels in water pumping has environmental impacts on nature, which the type and extent of these effects has particular importance.
Due to the importance of the water role, its required energy in crop production and the environmental effects, this research was conducted regarding Life Cycle Assessment (LCA) for evaluating the potential effect of irrigated wheat in Isfahan province, during the crop year of 2017-2018. To obtain the information needed in this study, questionnaires were designed by interviewing a number of experienced farmers, irrigation experts, and agricultural technicians. Then, the questionnaire was given to wheat farmers in 24 counties of Isfahan province. The selection of farmers who completed the questionnaires was performed using a systematic (regular) random sampling method. Based on questionnaires information, the amount of energy consumed in extraction of water needed for wheat cultivation in 24 counties of Isfahan province was investigated and calculated. In addition, environmental effects of extraction and water transfer on wheat cultivation fields were also estimated. According to the results, the highest and lowest energy ratio of water consumption with amount of 10.73 and 1.4 was obtained in Lenjan county and Aran and Bidgol, respectively. This ratio was obtained about 3.3 for the provincial average. In other words, by consuming of each unit of water energy in the province, 3.3 units of grain and wheat straw energy are produced. One of the reasons that caused diversity in energy ratios in different cities of the province was the difference between wheat yield and water pumping energy. In some counties such as Aran and Bidgol, due to climatic conditions and water and soil quality, wheat yield and consequently its energy extracted were less than other counties. But, in some geographical locations of the province, the water level was significantly lower than the other places, which increased the energy for pumping water. The study of water energy productivity showed that its value varied from 0.10 kg/MJ in Aran and Bidgol counties to 0.79 kg/MJ in Lenjan county. The average of this parameter in the province was 0.24 kg/MJ. According to the results, the group of global warming effect due to water consumption for producing of one ton wheat in Isfahan province varied from 44.87 to 736.9 kg of equivalent carbon dioxide, respectively in Lenjan county and Aran and Bidgol county. Its provincial average was 375.26 kg of carbon dioxide equivalent. The value of acidification potential varied from 0.29 to 4.88 kg of equivalent sulfur dioxide, respectively in Lenjan county and Aran and Bidgol county. Its provincial average was 2.49 kg of equivalent sulfur dioxide. The terrestrial eutrophication potential varied from 0.18 to 2.98 kg of equivalent nitrogen oxides, respectively in Lenjan county and Aran and Bidgol county. The provincial average of the terrestrial eutrophication potential was estimated to be 1.51 kg of equivalent nitrogen oxides. The depletion of fossil resources duo to water consumption varied from 141.94 MJ (Lenjan county) to 2335.39 MJ (Aran and Bidgol counties) and its provincial average was 1189.29 MJ per ton of wheat. The depletion of water resources effect, which represents the water consumed per ton of wheat seed production, varied from 1373.81 m3 (Lenjan county) to 2933.38 m3 (Semirom county) and its provincial average was 1987.12 m3. The lowest and highest Environmental index (Eco-index) of water consumption in wheat was 0.02 (Lenjan county) and 0.33 (Aran and Bidgol county), respectively, with a provincial average of 0.16. There are several ways to increase energy productivity in water consumption.
In conclusion, any action to increase performance or reduce energy consumption will improve productivity. These activates can be divided into two areas: water pumping conditions and wheat production conditions. In the first part, activities such as installation of pumps and motors in accordance with the pumping conditions and repair or replace worn-out parts of the pump and motor can be done. In the second part, modify of the cultivation pattern with consideration of water resources limitations, use of varieties with less water requirement and resistant to drought stress, and finally increase in the efficiency and productivity of water consumption are the important steps to increase wheat yield or replace it with productive crops.