Comparison of Energy Productivity and Global Warming Potential in Rain-fed Sunflower (Helianthus annuus L.) Production Systems

The main objective in agriculture production, so far, focused mostly on the increase of yield and production. Whereas today, economical and sustainable production is more important with regard to product quality, reduction of input consumption, conservation of natural resources and environment. Conservation tillage methods stabilize the soil productivity, reduce greenhouse gas emissions and protect the environment. The atmospheric concentration of greenhouse gases (GHGs) has been increased considerably in recent year's, as a result, human activities. Carbon dioxide (CO2) is the most important anthropogenic GHG; its annual emissions increased by about 80% between 1970 and 2004. Conservation tillage systems are increasingly considered as sustainable options to reduce the aftermaths of improper soil tillage. The objective of this study was to investigate energy flow and greenhouse gases emissions of sunflower production in three different tillage methods in northeastern part of Iran.

In order to evaluate the effect of three methods of sunflower production (conventional tillage and sowing, reduced tillage and direct seeding method) on energy consumption and global warming potential in rainfed conditions, this study was performed in the Kalpoosh of shahrood. Data were gathered from thirty representative fields by using a face-to-face questionnaire method and monitoring production practices and inputs used. After gathering of data, energy parameters and global warming potential were calculated based on CO2 balance. The energy amount of each input was calculated by multiplying the amount of consumed input on energy's equivalent. The output energy of sunflower was calculated by multiplying the crop yield on energy's equivalent. Other calculations of inputs and outputs in each method performed by energy coefficients.

The results indicated that total input energy in the conventional method, reduced tillage, direct seeding were 13169, 11814 and 10600 MJ.ha-1, respectively. Thus, conventional method had the highest rate of energy consumption (30 % higher than of direct seeding). Similar results reported by some researchers. The highest amount of total energy input related to nitrogen fertilizer and diesel fuel. Seedbed preparation had the highest rate of fuel and energy consumption (43.5 %) followed by nitrogen Fertilizer (37.6). Maximum of direct and indirect consumed energy, related to fuel and nitrogen, respectively. Similar results reported by some researchers. In three tillage methods, the share of irreproducible energy was the highest and small share of total energy consumption related to renewable energy. Rajabi et al. (2011) reported similar results. The energy efficiency of conventional method was less than other methods. This is due to the high share of machinery and fuel energy and greater use of workers and low yield per hectare. Reducing inputs consumption can be increased efficiency in agricultural systems. Feyzbakhsh and Soltani (2013) reported similar results. Maximum and minimum of energy productivity related to direct seeding (0.15 kg.MJ-1) and conventional method (0.11 kg.MJ-1), respectively. Maximum and minimum of global warming potential (GWP) was related to conventional method (1731 Kg.CO2 eq.ha-1) and direct seeding (1405 Kg.CO2 eq.ha-1), respectively. This issue is compatible with more fuel consumption in conventional method compared with direct seeding. In conventional method, the most rate of GWP was related to fuel consumption (44.8%) followed by nitrogen fertilizer (38.8%) and farm machinery (8.3%).

Based on this study results, through reducing of fuel consumption (replacing of obsolescent machinery and usage of modern implement, performing of farm operations in suitable soil moisture content and preventing of additional operations) and accurate consuming of nitrogen (according to soil testing), it is possible to reduce fuel consumption, greenhouse gas emission and environmental pollutions.