Integration of competitive cultivars and living mulch in sunflower (Helianthus annuus L.): a tool for organic weed control

Abstract

Selection of highly competitive cultivars (Cvs) of sunflower might limit weed growth. However, competitive ability alone may not be sufficient in suppressing weeds in sunflower. Competitive cultivars may have to be combined with other complementary management strategies such as selection of appropriate living mulch species. Two experiments were conducted to evaluate the combined effects of crop cultivar and living mulch on weed growth and sunflower yield. Three sunflower cultivars (Allstar, Azargol, and Farokh) and three living mulch treatments (intercropping of buckwheat, snail medic, and hairy vetch as living mulch) were evaluated in a factorial design. For each cultivar, a plot without living mulch (sole sunflower) was considered as weedy check. The sunflower cultivars significantly differed in their competitive ability against weeds. The Cv. Azargol has a superior competitive ability than Allstar and Farokh, on the basis of its impact on crop grain yield and weed infestation level. The highest grain yield (7126 kg ha−1) was obtained in Cv. Azargol. All living mulch species also reduced weed biomass and density compared to weedy check. This research revealed that use of buckwheat as living mulch caused the most inhibition effect on weed biomass and density. Overall, selection of Azargol as a competitive cultivar and buckwheat as living mulch which provided 96 % control was the best combination method for broadleaf weed control, while Farokh-buckwheat, which provided 77 % weed suppression was more effective combination for grass weeds. Our findings suggest that combining highly competitive sunflower cultivars with proper living mulch species is a feasible weed management strategy; however, selection of both crop cultivar and living mulch species should be adapted based on dominant weed spectrum.