Greenhouse Gases Emission and Global Warming Potential as Affected by Chemicals Inputs for Main Cultivated Crops in Kerman Province: I- Cereal

Agriculture is a major consumer of chemical resources. Increasing use of the inputs in agriculture has led to numerous environmental problems such as high consumption of nonrenewable energy resources, loss of biodiversity and pollution of the aquatic environment (Moradi et al., 2014). This environmental change will have the serious impacts on different growth and development processes of crops. The latest report of the Intergovernmental Panel on Climate Change (IPCC) states that future emissions of greenhouse gases (GHGs) will continue to increase and cause to climatic change (IPCC, 2007). This condition is also true for Iran. The three greenhouse gases associated with agriculture are carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Consistent with the development of agricultural production systems and move towards modernization in this sector increased dependence of the chemical resource (Salinger, 2005). There is even less data on CO2, N2O, and CH4 gas emission analysis as affected by cultivating various crops in Kerman province. Therefore, this study was conducted to assess the greenhouse gases (GHGs) emission and global warming potential (GWP) caused by chemical inputs (various chemical fertilizers and pesticides) for cultivating wheat, barley and maize in some regions of Kerman province at 2011-2012 growth season.
The study was conducted in Kerman province of Iran. Information about planting area of potato, onion and watermelon in various regions of Kerman was collected. Data were collected from potato, onion and watermelon growers by using a face to face questionnaire in 2014 for different regions of Kerman. In addition to the data obtained by surveys, previous studies of related organization (Agricultural Ministry of Kerman) were also utilized during the study. The application rates of the chemical inputs were collected by using a face-to-face questionnaire in various regions (Bardsir, Bam, Jiroft, Kerman, Ravar, Rafsanjan and Sirjan) of Kerman province. The amounts of GHG emissions from chemical inputs in the studied crops were calculated by using CO2, N2O and CH4 emissions coefficient of chemical inputs. Each greenhouse gas, i.e. CO2, CH4 and N2O has a GWP, which is the warming influence relative to that of CO2. The emission was measured in terms of CO2. The GWP coefficient based on CO2 is shown in Table 1.
The results showed that N and P fertilizers had the highest application share of chemical inputs. Maize had the significant different with wheat and barley based on N application per hectare. P application for maize and wheat was about 58 and 28% more than barley.
In all conditions, CO2 was obtained extremely higher emission rather than N2O and CH4. This issue was due to the highest coefficient emission of CO2 compared to N2O and CH4. Due to higher usage value and coefficient emission of N fertilizer, GHGs emission for N fertilizer was higher than the other inputs in all three crops and all the regions. The pesticide inputs had lower GHGs emission in comparison with chemical fertilizers. The highest emission of CO2, N2O and CH4 was gained for wheat fallowed by maize, and barely had the lowest value. Jiroft and Rafsanjan were obtained the highest and lowest GHGs emission through the studied regions, respectively. Higher GHGs emission in Jiroft was due to the higher planting area compared with the others regions. Annual GWP in studied regions and cereals had the same trend with GHGs emission, whereas, the highest and lowest values of GWP per hectare were related to Jiroft and Sirjan, respectively. The GWP in maize (504 t. ha-1) was higher than wheat (404 ton.ha-1) and barely (431 ton.ha-1). Among the chemical inputs, N fertilizer brought about 87% of GWP.
Generally, the results showed that nitrogen fertilizer is the most important factor in greenhouse gas emissions in cereal. Corn cultivation has more share than wheat and barley in the global warming potential. According to this research, the following strategies can be considered for reducing greenhouse gas emissions: Improvement of the nitrogen use efficiency
Use of crop rotations: Use of organic (manure, compost, green manure, plant debris) and bio (nitrogen fixation microcrystalline) resources than chemical fertilizers
Use of ecological and biological methods for pest and weed management
Use of intercropping systems