Energy use and input–output costs for sunflower production in sole and intercropping with soybean under different tillage systems

• Conventional tillage generated the highest output energy.
• Conservation tillage improves energy use efficiency and total LER.
• Intercropping enhances energy use efficiency, energy profitability and total yield.
• Co-application of intercropping and conservation tillage decreased energy consumption.
• Conservation tillage and intercropping co-application is a viable strategy.

Agriculture is an important energy user and energy supplier in the form of bio-energy. In today’s agricultural practices, soil tillage and applications of chemicals are the greatest consumers of energy and labor. Therefore, selection of an appropriate tillage method and finding an efficient way for decreased consumption of chemicals can improve energy use and reduce costs. The pre-requisite for such improvements includes assessment of the system's energy balance. Moreover, intercropping can play an important role in improving yield and reducing energy consumption. To compare the effects of different tillage treatments on energy use and grain yield in a sunflower-soybean intercropping system, a field experiment was performed on a clay loam soil at the Agricultural Research Station, Faculty of Agriculture, University of Bu-Ali Sina, Hamedan, Iran, during the growing seasons of 2013 and 2014. Three levels of tillage, as the main factor, and different planting patterns were tested in sub-plots (sole crop of sunflower, sole crop of soybean, and additive intercroppings of sunflower + 30%, 60% and 90% soybean). The intercropping design was additive. Results showed that sunflower grain yield was significantly affected by the planting pattern. Tillage treatments did not have significant effects on the sunflower yield. The highest sunflower grain yield (356.22 g m−2) was obtained from the sole crop of sunflower. Furthermore, amongst intercropping treatments, the highest sunflower grain yield (302.44 g m−2) was achieved from the combination of sunflower + 60% soybean. Also, comparison of the combined treatments indicated that the highest energy output (248363 MJ ha−1) and energy use efficiency (7.44) were reached with the combinations of conventional tillage × sunflower + 90% soybean, and minimum tillage by disc × sunflower + 90% soybean, respectively. In conclusion, using minimum tillage and intercropping system of sunflower + 60% soybean can decrease energy consumption and increase total yield and land use efficiency when compared to sunflower sole crop under conventional tillage.