Enhancing grassland diversity using slot-seeding and harrowing

Most grasslands in the UK are productive, species-poor communities resulting from intensive agriculture. Reducing the intensity of management under agri-environment schemes has often failed to increase the botanical biodiversity. The main reasons for this are seed limitation and a lack of suitable sites for establishment where competition remains low. We investigated the effectiveness of two low-cost approaches currently recommended for large-scale sward diversification, namely slot-seeding and harrowing with oversowing, on a productive, hay cut grassland in central England. We examined interactions of the restoration treatments with contrasting intensities of aftermath sheep grazing. Slot-seeding without a herbicide band spray proved to be the least effective means of introducing desirable species into productive grassland. In contrast, both slot-seeding with herbicide band spray and harrowing were equally effective means of establishing sown species. Slot-seeding requires more specialised machinery, but uses a lower seed rate which is significantly cheaper than harrowing and oversowing. There were very few significant effects of the contrasting intensities of sheep grazing on the establishment of sown species.