Enhancement of botanical diversity of permanent grassland and impact on hay production in Environmentally Sensitive Areas in the UK

Five methods for increasing the botanical diversity of permanent grassland, either by sowing site-specific species-rich grass/forb seed mixtures (stri p-seeding; or over-sowing after sward disturbance by light harrowing, parti al rotary cultivation or turf removal), or by introducing transplanted plug plants, were compared with a control treatment in replicated field experim ents on six farm sites in Environmentally Sensitive Areas (ESAs) in England and Wales. Effects on herbage production under hay cutting in July and on botanical composition were recorded in the two subsequent years. Turf remov al before sowing was the only treatment that significantly reduced herbage production; this treatment also had the greatest effect on increasing botan ical diversity (to a mean of twenty-eight plant species per site compared w ith fifteen species for the control 2 years after sowing). The least succes sful establishment of sown species resulted from light harrowing before sow ing; the rotary-cultivated and strip-seeded treatments increased species di versity, although by less than turf removal. Successful establishment of in troduced species was greatest on sites having a low soil nutrient status. S pecies that established successfully from seed on most sites and treatments included the grasses Alopecurus pratensis, Cynosurus cristatus, Festuca ru bra and Phleum pratense, and the forbs Achillea millefolium, Leucanthemum v ulgare, Plantago lanceolata and Prunella vulgaris; in addition, Centaurea n igra, Hypochoeris radicata and Lotus corniculatus were also established by one or more methods on most sites, Lychnis flos-cuculi established successf ully on mesotrophic sites, and Medicago lupulina on calcareous sites. Sever al species failed to establish at all or most sites where they were sown, e .g. Helianthemum nummularium, Pimpinella saxifraga and Rhinanthus minor. Mo st transplanted plug-plant species established successfully in the short te rm, but many failed to persist or their frequency in the sward remained low ; exceptions included A. millefolium and P. lanceolata. The results are dis cussed in relation to the requirements for management to further the object ives of ESAs and agri-environmental schemes.