engleski

Effects of reduced herbicide doses on annual weeds and winter wheat yield by two tillage

The effects of dose reduction on the efficacy of triasulfuron + chlortoluron, iodsulfuron- methyl sodium + mefenpyr-diethyl and izoproturon + beflubutamid mixtures in the post-emergence control of annual weeds and winter wheat yield were compared in two tillage systems (mouldboard ploughing - CT ; disk harrowing - RT) in north-eastern Croatia. The three-year average, total weed density in RT tillage was for 37% or 3.6 plants m-2 greater compared to 9.7 plants m-2 in CT tillage. In both tillage systems the main species were the grass of Apera spica-venti and broad-leaved weeds of Ambrosia artemisiifolia, Chenopodium album and Matricaria inodora. The efficacy of herbicide mixtures and their rates did not significantly vary between two tillage systems. All three herbicide mixtures provided the best weed control with the highest recommended rates, which corresponded on average to a 97 - 99% weed control, compared to untreated plots. The dose reduction to one half decreased the efficacy by 6 -15 percentage units on average, which corresponded to a 82 - 93 % of weed control. One-third dose, which corresponded to a 75 - 87% of weed control, decreased the efficacy by 12 - 23 percentage units in relation to the full dose. On average, all herbicide mixtures at full and one-half rates gave similar yields of 6247 kg and 6133 kg ha- 1, respectively, without any significant differences. Regardless of herbicides, a dose reduction to one-third of the recommended one caused a variation in control efficacy, which mainly depended on weather conditions and crop competitiveness. The average decrease in yield at one-third herbicide dose was 6%, compared to the yield with the highest recommended dose. Total weed density did not increase after three continuous years of using reduced herbicide doses.

Winter wheat ; tillage ; triasulfuron + chlortoluron ; iodsulfuron-methyl sodium + mefenpyr-diethyl ; izoproturon + beflubutamid ; herbicide dose rates ; weed density ; crop density ; crop yield

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