assessing energy flow in rainfed and irrigated wheat fields of shahrekourd township under two tillage systems

introduction energy analysis of agricultural ecosystem is essential for sustainable production. the relation between agriculture and energy is very close. agriculture is an energy consumer and the energy supplier. agriculture’s use of energy is recognized in three external inputs: labor, machines, and fertilizers (connor et al., 2011). significant gains in energy efficiency were arisen in agriculture following the phenomenal increase in energy prices in the 1970s. greater use of diesel motors, larger tractors, using conservation tillage methods and optimized fertilizer use efficiency were the main causes (ozkan et al., 2004). safa & samarasinghe (2013) were reported that fuel consumption in tillage and harvesting was more than other operations in wheat fields of canterbury, new zealand. effective application of agricultural techniques and efficient use of support inputs can minimize environmental problems and in consequence promote sustainable agricultural intensification. in this study, the energy flow investigated in irrigated and rain-fed wheat cropping systems under two tillage and no-tillage methods in the shahrekourd city, during 2013. materials and methods the study was carried out in the sharekourd city (chaharmahal bakhteyari province). this region is located within 32º 20' and 32º 21' lat. n, 50º 48' and 50º 50' lon. e. data were collected from 40 farmers with questionnaire method. in this study, a randomized complete design with four scenarios (rain-fed and irrigated farming with tillage and no-tillage systems) was used, that 10 farms were considered as a replication in each scenario. all data detail information on the questionnaire were averaged and arranged. first, all inputs and outputs of wheat production were determined, quantified and entered into microsoft excel spreadsheets, and then transformed into energy units and expressed in mj.ha-1. based on the total energy equivalents of the inputs and output and the energy use efficiency (energy ratio), net energy, energy productivity and specific energy were calculated. the input energy was divided into direct, indirect, renewable and non-renewable forms. indirect energy included energy embodied in seed, fertilizers, chemicals, machinery; while direct energy covered human labor, water for irrigation, electricity and diesel fuel were used in the wheat production. the lsd test (p≤0.05) was used to compare means between all scenarios. results and discussion the results of data analysis indicated that maximum input energy was about 29,586 mj.ha-1 in the irrigated fields under tillage and maximum output energy was about 70,743 mj.ha-1 in the irrigated fields under no-till. in this study, the highest and lowest energy efficiency were obtained in irrigated system under no-tillage (2.43 in seed) and rain-fed system under tillage (1.03 in seed), respectively. the greatest contribution from total energy belonged to energy of nitrogen fertilizer (9,429 mj.ha-1 in no-tillage and 1,092 mj.ha-1 in tillage systems) and irrigation (8,323 mj.ha-1 in no-tillage and 5,117 mj.ha-1 in tillage systems) in irrigated cropping system and nitrogen fertilizer (8,529 mj.ha-1 in no-tillage and 7,220 mj.ha-1 in tillage systems) and seed (4,367 mj.ha-1 in no-tillage and 2,412 mj.ha-1 in tillage systems) in rain-fedfarming system. therefore, it is necessary to focus more on nitrogen fertilizer consumption than the other factors to effectively reduce energy consumption in wheat cropping. in addition, the no-tillage system had high indirect and non-renewable energy forms in both wheat cropping systems. the high ratio of non-renewable energy in the total used energy inputs cause negative effects on the sustainability in agroecosystems. conclusion generally, irrigated cropping system under no-tillage method was the best condition for wheat production in shahrekourdcity. the results revealed that there was a huge potential toimproveenergy efficiency of wheat production in this region. furthermore, toreducenon-renewable energy use in the studied region, we recommended the use of chemical fertilizer specially nitrogen reduce by appropriate management of fertilizer, use of legume in crop rotation, use of green manure, organic fertilizer and manure. acknowledgements we are grateful to agriculture service centers of shahrekourd and gorgan university of agricultural sciences and natural resources (guasnr).