Effect of Conservation Tillage and Intercropping with Beans and Soybeans on Weed Competition, Production Potential and Water and Nitrogen Use Efficiency of Sunflower

For increasing sunflower competitiveness to weeds, potential of production and water-nitrogen use efficiency through intercropping of bean and soybean under conservation tillage system, an experiment was conducted at the Agricultural Research Station, Faculty of Agriculture, Bu-Ali Sina University, during 2013 and 2014 growing seasons. Experiments were conducted as split plot based on randomized complete block design with three replications. Tillage as conventional tillage, reduced tillage by chisel and reduced tillage by disc) and different planting patterns :sunflower sole cropping with weeding, sunflower sole cropping without weeding, additive intercroppings of 30, 60 and 90%bean, as well as 30, 60 and 90%soybean with sunflower were considered as main plots and sub-plots, respectively. Results showed that the highest total weed density and biomass values were observed at reduced tillage and sole cropping treatments. However, conventional tillage and intercropping system were able to decrease density and biomass of dominant weeds, such as pigweed, foxtail and bindweed. Considering to the increasing total yield of intercropping (the sum of the yield of main and associated plants), these systems increased water and nitrogen use efficiency in comparison with sunflower sole cropping without weeding. The land equivalent ratio (LER) was calculated to measure efficiency of intercropping compared to sole cropping. Based on our findings, >30%bean: sunflower or >30%soybean: sunflower combination showed grain yield advantage (LER>1). In conclusion, our results suggest that under similar and favorable conditions, applying a combination of conservation tillage and intercropping to sunflower cultivation can improve weed management and increase the economical yield and land use efficiency when compared to sunflower sole crop under conventional tillage.