Arable flora in sprayed and unsprayed crop edges

On 15 conventionally managed arable farms in an intensive arable farming district on marine clay in the Netherlands, edges of winter wheat, sugar beet and potato crops were either sprayed or unsprayed with herbicides and insecticides, during the period 1990-1994. The presence (frequency) and abundance (ground cover) of farmland plant species within sprayed and unsprayed edges and in the sprayed field centre were compared. In all three crops, leaving 3-6 m wide edges unsprayed, both the presence and abundance of farmland plants increased, by factors of 4.8-12.1 and 1.5-2.7, respectively. The effect was greatest in the winter wheat crop. The increase was attributable mainly to dicotyledonous species. Although the majority of the plants were common farmland species, there was a major enhancement of the floristic value of the unsprayed fields. In the sprayed centres of the fields, the presence and abundance of farmland plants as well as the overall floristic value were consistently lower than in the sprayed and unsprayed edges. Leaving the crop edges unsprayed significantly decreased crop cover in sugar beet fields only. If compatibility with farm management is also taken into account, the measures investigated appear to have the greatest potential in winter wheat. (C) 1997 Elsevier Science B.V.