Botanical development of restored species rich field margins

Starting in 2007 species rich field margins shall be introduced as a new, enduring ecological compensation area type in Swiss agriculture. The results of large on farm-experiments with different seed mixtures and cutting regimes showed the highest plant species diversity under fresh and dry soil conditions while on clay soils and under more humid or particularly shady conditions the species richness was diminished and grasses were highly dominant. With the seed mixture for dry to fresh sites the aimed species diversity of 20 sown species per 25 m2 was reached in most cases.Mowing in summer compared with no mowing did not affect species composition or the portion of forbs and grasses. Cutting in August allowed many forbs and legumes a second flowering period thus enhancing the attractiveness of the field margins and diversity. The only problematic weeds detected in the margins were Rumex obtusifolius, Cirsium arvense and Agropyron repens. While the number of plots with the three species present increased between 2002 and 2004, the cover remained constant.