Soil acidification—the use of sulphur and acidic plant materials to acidify arable soils for the recreation of heathland and acidic grassland at Minsmere, UK

Abstract

Attempts are being made to restore heathland and acid grassland on arable land at the Minsmere reserve of the Royal Society for the Protection of Birds (RSPB). Experiments were conducted to acidify the arable soils (pH 6–7) to heathland levels (pH 3.5–4) by the addition of varying amounts of elemental sulphur (S), bracken litter and pine chippings. All rates of S addition reduced soil pH, although the efficacy of acidification was related to the application rate. Rates of 1 and 2 t S ha −1 produced soils of c. pH 4. Rates of 8 t S ha −1 and above reduced the soil pH to <pH 3. Equations were derived for two fields to enable calculations of the S additions required to reduce pH to a given value. Bracken litter reduced soil pH to 4–4.5, and pine chippings reduced the soil pH by 0.5–1 unit to pH 5.5. The addition of pine chippings was not an effective means of acidifying the soil where large reductions in pH are needed. Soil acidification did not significantly increase the available concentrations of Ca, Mg, K and P, indeed reductions in extractable P and exchangeable Ca were found, which may aid the establishment of heathland and acid grassland species. The reduction in soil pH brought about by the addition of bracken litter was not sufficient to inhibit the growth of arable weeds that compete with heathland vegetation. S was the most effective means of acidifying the soil, but at high application rates caused acidification through the soil profile, which could be problematic should leaching occur into water courses. A combination of low rates of S application coupled with the addition of bracken litter may offer the best solution, although further experiments are needed to test this approach.