Weed emergence on long years’ not herbicide treated fields - duration of the after-effects

Abstract

In a long-term field trial plots were not treated with herbicides for 12 years (from 1996 to 2007). Two different crop rotations with 50% or 66% of cereals in the rotation were tested. At the same time in each crop rotation two different plant protection strategies were established. Since autumn 2007 the former controls not sprayed with any herbicide have been treated with herbicides. The crop rotation was unified. In that long-term field trial plots always treated with herbicides exist also. Weeds were counted by number and species before herbicide treatments. The comparison of these two different plots (treated and untreated) shows what after-effect exists on the formerly untreated plots even after eight years. The emergence of weeds is still higher. Also the different crop rotations are still perceptible. For the plant protection strategy with the lower herbicide amounts the differences blur now.

Keywords

• crop rotation
• long-term field trial
• plant protection strategy
• untreated control