Effects of crop rotation, herbicide application and nitrogen on the emergence of Vicia spp.

A long term field trial regarding crop rotations, application of fertilizer and pesticides was established in 1998 at the Julius Kühn-Institute experimental field in Dahnsdorf. The experimental field is located in the state of Brandenburg (Germany) about 50 km from Berlin. The long-term field trial consists of two crop rotations: (A) peas – winter barley – winter rye – white clover (for some years fallow) - winter barley – winter rye and (B) continuous cropping of winter rye. In both crop rotations the experimental treatments are: 1) no fertilizers - no pesticides, 2) no fertilizers - pesticides, 3) fertilizers - no pesticides and 4) fertilizers – pesticides. Weeds are counted in autumn or spring; in the treatments with herbicide application also before herbicide application. Both weed species and number are determined. The influence of the crop rotation regarding the weed infestation was strongest for treatment 1) and declined with fertilizer and pesticide use. The crop rotation (A) generally showed lower Vicia spp. infestation, while the continuous cropping of winter rye (B) promoted Vicia spp.. The infestation was very different throughout the years. The numbers per m² ranged from 0 up to 144.8 in treatment (B) (continuous cropping of winter rye) with no fertilizers and no pesticides (1).