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High soil pH has been highlighted as a constraint to the restoration of heathland on ex-arable land. Previous studies at the Minsmere Reserve of the Royal Society for the Protection of Birds (RSPB) in England have shown that it is possible to acidify ex-arable soils using elemental sulfur and bracken litter, although sulfur (S) is more effective. Current recommendations suggest that 4 tS/ha need to be applied to reduce soil pH below pH 4, control vigorous ruderal species, and create conditions suitable for Calluna vulgaris (heather) establishment. However, S is relatively expensive, and as bracken litter is moderately abundant within the reserve, it made economic sense to evaluate the potential for mixing S with bracken to see if adequate pH reductions could be achieved at lower S rates. Accordingly an experiment was designed to test the effects of combining S (0-8 t S/ha) and bracken litter (0-10 cm depth layers) on (1) soil pH, (2) cover of ruderal species, and (3) the developing plant community. Significant interactions were detected, especially in the period immediately after application. Where bracken litter was applied the soil pH fell immediately; in contrast, S took at least six months to start reducing pH. Where mixtures were applied there was a synergistic effect, which produced a lower pH than the S or bracken litter applied alone. These effects were most marked at low S application rates, between 0.5-4 t S/ha. The effects of the bracken litter addition also reduced the growth of ruderal species in the period immediately after application, probably through a combination of acidification and physical smothering. There is, therefore, a clear potential to acidify ex-arable soils using combinations of S and bracken litter in schemes designed to restore Calluna heathland.

Abstract. Minsmere is a large nature reserve in East Anglia UK, owned and managed by the Royal Society for the Protection of Birds (RSPB). Two blocks of land, which were farmed commercially until 1990, have been bought in an attempt to link existing patches of heathland and acid grassland, thus creating a larger area for conservation. This paper discusses methods for the creation of acid grasslands. Previous studies of the arable soils in these fields identified three constraints ‐a depauperate seed bank, a high pH and vigorous growth of ruderal species after the fields were abandoned. Accordingly, experiments were set up to test the effects of (1) adding seed of species typical of acid grasslands and (2) adding amendments (elemental sulphur, litter of Pteridium aquilinum and pine chippings) to acidify the soil. The results confirmed that ruderal growth was high on unamended plots, but this could be reduced by addition of acidic amendments. Where the cover of ruderals was reduced, the cover of the sown species increased. The sown species colonized adjacent unsown subplots naturally and this was most pronounced where the acidity had been reduced by treatment. The most effective treatment was 21 S/ha, which gave the optimal reduction in soil pH, controlled ruderal growth and provided a reasonable cover of the sown species. The addition of Pteridium litter or pine chippings gave good establishment of sown species, but control of the ruderals was less effective.