بررسي انتشار گازهاي گلخانه اي و پتانسيل گرمايش جهاني ناشي از مصرف نهاده هاي شيميايي در زراعت محصولات مهم استان كرمان: I - غلات

Greenhouse Gases Emission and Global Warming Potential as Affected by Chemicals Inputs for Main Cultivated Crops in Kerman Province: 1- Cereal

در اين تحقيق، ميزان انتشار گازهاي گلخانه اي و پتانسيل گرمايش جهاني ناشي از مصرف نهاده هاي شيميايي در زراعت گندم (Triticum aestivum L)، جو (Hordeum vulgare L) و ذرت (Zea mays L) براي استان كرمان در سال زراعي 92-1391 مورد بررسي قرار گرفت. اطلاعات مربوط به سطح زير كشت محصولات مذكوردر شهرستانهاي مختلف استان كرمان از طريق آمار سازمان جهاد كشاورزي استان استخراج گرديد. ميزان كاربرد نهاده هاي شيميايي شامل نيتروژن، فسفر، پتاسيم، علف كش، حشره كش و قارچكش توسط پرسشنامه ها و مصاحبه حضوري از شهرستان هاي مختلف استان جمع آوري شد. انتشار گازهاي گلخانه اي دي اكسيدكربن (CO2)، اكسيدنيتروژن (N2O) و متان (CH4)و همچنين پتانسيل گرمايش جهاني در محصولات مورد بررسي بر اساس ميزان مصرف نهاده، ضرايب انتشار و سطح زير كشت محاسبه شد. نتايج نشان داد كه در هر سه محصول مورد بررسي ميزان انتشار گازهاي گلخانه اي ناشي از مصرف كود نيتروژن بيشتر از ديگر نهاده ها بود. ميزان انتشار CO2، N2O و CH4 در گندم بيشتر از ذرت و آن هم بيشتر از جو بود. در بين شهرستان هاي مورد بررسي، جيرفت و رفسنجان به ترتيب بيشترين و كمترين ميزان انتشار را دارا بودند. ميزان ساليانه پتانسيل گرمايش جهاني در مناطق و غلات مورد بررسي مطابق با روند انتشار گازهاي گلخانه اي بود. در حالي كه، ميزان اين شاخص در هكتار، در شهرستانهاي جيرفت و سيرجان از بيشترين و كمترين ميزان برخوردار بود. ميزان پتانسيل گرمايش جهاني بر حسب معادل CO2 در ذرت (504 تن در هكتار) بالاتر از گندم (404 تن در هكتار) و جو (431 تن در هكتار) بود. در بين نهاده هاي مورد بررسي، كود نيتروژن حدود 87 درصد پتانسيل گرمايش جهاني را باعث شد.

Introduction: 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. Materials and methods: 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. Results and discussion: 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. Conclusion: 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.