Mekanisk og Kemisk ukrudtsbekæmpelse / Mechanical and Chemical Weed control
In average of six trials four sprayings have controlled all weed and maximum yield is achieved. Tractor pulled hoeing in combination with four sprayings show a tendency to yield reduction until 3 percent. Hoeing has increased yield when weed is present where only one, two or three sprayings has been executed. In two trials one spraying has been sufficient to control the weed, but those trials are not representative.
Based on the present and earlier trial results a model to describe the relation between weed cover and relative sugar yield has been developed. The trial results show if more than 2 percent of the soil surface is covered by weed after maximum efficacy on weed is reached after finalised weed control or 2 percent of the canopy is covered by weed in august yield losses is likely to occur. This is an adaptation of previous thresholds.
The fourth spraying may be substituted by one or two mechanical hoeing’s still achieving maximum yield. This will reduce the Danish treatment index by 28 percent in the present trials. Further reduction may be achieved by using band spraying in combination with mechanical hoeing.