Management regimes and farming practices enhancing plant species richness on ditch banks

Plant species richness of ditch banks under different farming practices and management regimes was compared. To this end, species richness was inventoried on ditch banks on Dutch conventional and organic farms and on a number of experimental farms. Plant species richness was significantly higher on organic than conventional farms. On farms that had converted to organic agriculture more than 5 years ago, even more species were found. On all farms, including the experimental farms, higher plant species numbers as well as a higher share of nitrogen poor plant species were found on sandy soils than on clay soils. Also a change in plant species composition was found based on the rarity index and the Ellenberg nitrogen values which was most marked in ecologically managed ditch banks on the experimental farms. The results, therefore, indicated that the ecological management might enhance plant species richness more than organic farming alone in a 6-year period. In the context of environmental label, criteria designed to enhance on-farm biodiversity should therefore specify an ecological management on ditch banks buffered with a pesticide and nutrient free zone.