Research is underway to develop cost-effective options for enhancing biological diversity in grassland undergoing extensification, with particular reference to ESAs. This study will aim to assess the impact of N, P, K and Ca fertilisers, together with grazing and cutting, on the rate and direction of changes in botanical composition and diversity of an upland sward, e.g. Bronydd Mawr. Success of introducing a range of key forbs into upland swards will also be measured, as well the influence of major nutrient and defoliation regimes. It is recommended that results of this low-input experiment should be verified on soils which are more typical of acidic upland ESAs. The project will advance understanding of ecological principles and mechanisms influencing biological diversity in grazed upland swards.