عنوان مقاله [English]
Nowadays, due to population growth, decreased the arable lands and improved living standards, energy consumption in the agricultural sectors has been increased. Therefore, intensive use of chemical fertilizers, pesticides, agricultural machinery, energy and natural resources are required in order to supply the nutritional demands of the increasing population. Ahamadi & Aghaalikhani (2013) investigated the energy consumption in cotton production in Golestan province and showed that energy consumption for tractor and engine pump fuel was 24% and 30%, respectively, or totally 54% for diesel fuel. Also, fertilizers and chemical materials with 13% energy consumption had the second and third rank, respectively and total energy input for cotton production in Alborz province was 31 GJ/ha. Dastan et al., (2014) carried out a study on the rate of energy consumption in rice planting systems and the rate of carbon dioxide emission and concluded that the highest values of energy input in the production systems was related to the electric power to pump water for irrigation that had the highest value in terms of carbon dioxide emission and global warming potential and Nitrogen fertilizer and fuel also had the second and third rank in terms of carbon dioxide emission.
Materials and Methods
One hundred cotton fields around the cities of Aliabad and Aq Qala in Golestan province were selected during two sowing years 2014 and 2015. All operations and events were observed during the growing season in these fields and detailed data of typical production methods and cultivation practices was collected in past years, this data included the use of equipment, fuel, fertilizers, and pesticides and so on. To this end, at first, all agricultural practices were divided into eight categories, including preparing the land, planting, fertilizing, plant protection, weed control, irrigation, harvesting and transport to the factory to crop delivery, then, different amounts of input use and more comprehensive information were collected and recorded at every stage from planting to harvesting and they were processed by Excel software, data analysis in three parts of energy input (consumption), energy output (production) and Global warming potential (GWP) of GHG emissions.
Results and Discussion
In this study, input and output energy of GHGs emission and the GWP of agricultural activities in the cotton fields of Golestan province were investigated. The results revealed that the average energy input per hectare is 26 GJ/ha and the ratio of output energy to input energy was 154 GJ/ha and energy output was six times more than the input energy. There was a direct relationship between input energy and energy output, in other words, an increase in energy input, increases the crop performance, thereby increasing the output energy and GHG emission (Table 5). Figure 11 shows a significant direct relationship between performance and GHG emitted from the cotton production. The average of the GHG emission for cotton production was estimated 2181kg/ha that the maximum rate was 33% of total GHGs of chemical fertilizer inputs. Fuel and manure inputs had lower rates. Maximum energy was consumed for irrigation, nutrition and preparation that increased the GHGs. The comparison between energy output and a GWP of manure input showed a significant direct relationship difference between the output energy in cotton farms and its GWP.
The results of this study indicated that by reducing the fuel consumption and chemical fertilizers, energy consumption and GHG emissions can be reduced. A number of management solutions for reducing the fossil fuel consumption and chemical fertilizers that result in GHG emission in agriculture include: conservation tillage that reduces the farm traffic, and consequently, reduces the fuel; use of legumes in agriculture that reduces nitrogen use, use of new methods of irrigation and increase in water efficiency, use of crop rotation and biological methods to control pests and weeds, application of nitrogen fertilizers based on soil test, adaptation of the fertilizing time to the plants' needs, improvement of fertilization methods such as placement in the soil rather than manual distribution and centrifuge, the use of inhibitors combinations of Nitrification or coated fertilizers, use of green manure.