Hard-water antagonism of trifloxysulfuron as affected by time gap between the addition of adjuvant and herbicide to the tank

This study aimed to assess the effect of a time gap between adding adjuvant and herbicide to the tank on hard-water antagonism of trifloxysulfuron under greenhouse conditions. Treatments consisted of herbicide dose (۰, ۰.۷۵, ۱.۵, ۳, ۶, and ۱۲ g ha-۱), spray carrier (distilled water ± ۶۰۰ mg MgCl۲, CaCl۲, and FeCl۳ L–۱), the order of adding adjuvant and herbicide to the spray carrier (herbicide alone, the addition of ۲۰ g ammonium sulfate L-۱ or ۳۰۰ mg citric acid L-۱ ۱۵ min before, at the same time, and ۱۵ min after adding trifloxysulfuron to the spray carrier). The dry matter of velvetleaf was regressed over the doses of trifloxysulfuron to obtain herbicide doses in which ۵۰ and ۹۰% velvetleaf control occur (ED۵۰ and ED۹۰, respectively). The presence of Mg۲+, Ca۲+, and Fe۳+ in the spray carrier increased the ED۵۰ from ۲.۴۱ to ۵.۰۷, ۷.۶۵, and ۹.۷۸ g a.i. ha-۱ and the ED۹۰ from ۵.۸۸ to ۱۶.۵۶, ۲۸.۴۸, and ۲۸.۱۹ g a.i. ha-۱, respectively, indicating a hard-water antagonism of trifloxysulfuron as Fe۳+ = Ca۲+ > Mg۲+. Generally, the best order was adding adjuvants ۱۵ min before adding trifloxysulfuron to the tank. It could completely overcome the hard-water antagonism of trifloxysulfuron. In contrast, the order of adding adjuvants ۱۵ min after adding trifloxysulfuron to the tank had no significant effect on overcoming the hard-water antagonism of trifloxysulfuron, resulting in additional costs for farmers.

Keywords:

ammonium sulfate , citric acid , spray water quality , velvetleaf