Abstract
Sunflower is an important industrial crop since it is grown all over the world for oil production, while Johnsongrass (Sorghum halepense (L.) Pers.) is characterized by great competitiveness and can severely impair plant growth and crop productivity. Thus, a two-year field experiment was conducted to evaluate the impact of Johnsongrass control practices on plant growth, seed yield, and oil content of sunflower crop. The results indicated that Johnsongrass competition negatively affected sunflower growth and productivity as the lowest values of height, dry biomass, seed, and oil yields were recorded at the weed-infested treatment, followed by the weed infested for 30 days after sowing. All the other treatments had a positive effect on vegetative and yield parameters. Moreover, fluazifop-p-butyl, quizalofop-p-ethyl, and the combination of fluazifop-p-butyl and imazamox effectively controlled Johnsongrass. Specifically, in 2020, the lowest dry weight of Johnsongrass was observed in the plots where fluazifop-p-butyl + imazamox were applied. Thus, the results of this study clearly showed that the use of the above-mentioned herbicides can improve the seed and oil yield of a sunflower crop by managing Johnsongrass, while the competition of this rapidly growing weed for a short period of 30 days can significantly reduce crop yield.
Highlights
Sunflower (Helianthus annuus L.) is an important industrial plant grown for oil production
Our results showed that the herbicides quizalofop-p-ethyl, fluazifop-p-butyl, and fluazifop-p-butyl + imazamox exhibited high efficacy against Johnsongrass (Figure 6e)
With regard to the effects of various control practices on seed yield and its components, our results indicated that the lowest values of seed yield, 1000-seed weight, and flower head weight were recorded in weed-infested treatment, while the high efficacy of herbicides fluazifop-p-butyl, quizalofop-p-ethyl, and fluazifop-p-butyl + imazamox against Johnsongrass had a beneficial effect on head weight and seed yield compared with the untreated plots
Summary
Sunflower (Helianthus annuus L.) is an important industrial plant grown for oil production. Various grass and broad-leaved weeds, as well as the parasitic weed broomrape (Orobanche cumana Wallr.), significantly reduce the seed yield of this crop [3,7–9] Weed control in this broadleaved crop is accomplished by cultural practices (e.g., competitive cultivars, mulching, and intercropping) [10,11] and the use of various pre- and post-emergence herbicides [12–14]. In this crop, the development of sunflower hybrids resistant to imidazolinones (Clearfield® technology) and sulfonylureas (ExpressSun® technology) has significantly contributed to weed control by the application of herbicides that inhibit the enzyme acetolactate synthase, like imazamox and tribenuron-methyl [9,15–17]. Jat and Giri [19] reported that the pre-emergence application of pendimethalin increased sunflower’s seed yield by 56.4% compared with the weedy control
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