Evaluation of the Effect of Additive Application on the Efficacy of Haloxyfop R-Methyl Herbicide on Narrow-Leaved Weeds in Saffron (Crocus sativus L.) Fields

Introduction: Saffron (Crocus sativus L.) is recognized as an important medicinal and commercial plant in Iran, particularly in arid and semi-arid areas. Weeds are recognized as a significant limiting factor in saffron production. Saffron suffers in its ability to compete with weeds for light, water, and nutrients due to its restricted vegetative development. Grass weeds are among the most significant and troublesome weeds affecting saffron. Significant and troublesome grass weeds in saffron fields comprise Hordeum murinum, Bromus tectorum, Hordeum spontaneum, Aegilops geniculata, and Lolium rigidum. The predominant technique for managing weeds in saffron fields is hand weeding, employed alongside other ways, including chemical approaches, due to its labor intensity, cost, and time requirements. Herbicide efficacy can be improved economically and effectively with adjuvants. Consequently, the application of adjuvants is suggested to improve the performance of herbicides that block acetyl-CoA carboxylase. Although a few studies have examined the efficacy of herbicides with additives in saffron cultivation, this study specifically investigates the effects of adjuvants combined with the herbicide haloxyfop R-methyl on grass weed density and biomass in a four-year-old field.
Materials and Methods: The research employed a factorial design based on a randomized complete block design with three replications in a four-year-old saffron field. Cultivation occurred in a 20 × 20 centimeter mound with a density of 4 corms per mound (equating to 100 corms per square meter). The research was conducted in a four-year-old field by using a factorial design based on a randomized complete block design with three replications. The first factor was haloxyfop R-methyl concentration at 0%, 50% (0.5 L or 54 g ai ha^-1), 75% (0.75 L or 81 g ai ha^-1), and 100% (1 L or 108 g ai ha^-1) of the recommended dosage (108 g ha^-1). The secondary factor was no additive, citogate oil, and corn oil (0.5% v/v). Corn oil was extracted using cold pressing, while Zarangaran Pars Company supplied citogate oil (an alkyl aryl polyglycol ether). Applications were conducted using a rechargeable sprayer calibrated with a uniform air nozzle (8002) at a pressure of 2 bars during the four-leaf stage of grass weeds. A plastic cover was employed prior to spraying to prevent wind drift. Broadleaf weeds were removed from all plots. Three plots were designated as no-weed control, whereas three plots were classified as complete weed control. Four weeks post-treatment, the quantity of grass weeds, including little seed canary grass (Phalaris minor), wild oat (Avena fatua), mouse barley (Hordeum murinum), and cheatgrass (Bromus tectorum), was enumerated by species, and their dry weight was assessed following a 48 h exposure in an oven at 75°C. The density of live grass weeds was measured. The efficacy of weed management was determined by assessing the reduction in density and dry weight of each treatment relative to its respective control. The statistical analysis of the data was conducted using SAS 9.4 software. The FLSD test was utilized to compare means at a significance level of 5%.
Results and Discussion: The analysis of variance results demonstrated the significant effect of the concentration of the herbicide haloxyfop R-methyl and adjuvant on the percentage reduction in the density of grass weeds in the saffron field, including mouse barley, wild oats, cheatgrass, little seed canary grass, and their total grass weed. The interaction effect between the herbicide concentration and the adjuvant was not significant only for wild oats; however, this interaction significantly influenced wild oats and cheatgrass at a 1% probability level, as well as the density of little seed canary grass and the overall count of grass weeds at a 5% probability level. An analysis of the treatment combinations, comparing complete weeding to no weeding, reveals an important difference in the percentage reduction of weed density. The application of citogate oil resulted in a 60.6% reduction in ryegrass density, 64.4% in wild oats, 60.4% in cheatgrass, and 76.5% in little seed canary grass, compared to the treatment without the adjuvant. The analysis of variance revealed that the basic impacts of herbicide concentration and adjuvant significantly influenced the percentage of dry weight decrease in all weeds. The interaction effect was significant only for ryegrass at p<0.01 and for little seed canary grass at p<0.05, but it had no significant impact on wild oats, cheatgrass, or the total dry weight of grass weeds. A significant difference was observed when examining the effects of treatment combinations with total weed control compared to no weeding on the percentage reduction of all weeds. In summary, the use of corn oil resulted in a reduction of the dry weight of mouse barley, wild oats, cheatgrass, little seed canary grass, and all grass weeds by 46.2%, 38.7%, 44.3%, 31.4%, and 23.7%, respectively, while citogate oil reduced the dry weight by 58.4%, 1.61%, 5.62%, 0.55%, and 7.47%, respectively.
Conclusion: The findings of this study indicate that the application of the herbicide haloxyfop R-methyl in conjunction with the adjuvant citogate enhances the efficacy of grass weed control.