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

Attempts are being made to restore heathland and acid grassland on arable l and at the Minsmere reserve of the Royal Society for the Protection of Bird s (RSPB). Experiments were conducted to acidify the arable soils (pH 6-7) t o heathland levels (pH 3.5-4) by the addition of varying amounts of element al 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. Ra tes 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 o f pine chippings was not an effective means of acidifying the soil where la rge reductions in pH are needed. Soil acidification did not significantly i ncrease the available concentrations of Ca, Mg, K and P, indeed reductions in extractable P and exchangeable Ca were found, which may aid the establis hment of heathland and acid grassland species. The reduction in soil pH bro ught about by the addition of bracken litter was not sufficient to inhibit the growth of arable weeds that compete with heathland vegetation. S was th e most effective means of acidifying the soil, but at high application rate s 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. (C ) 1998 Elsevier Science Ltd. All rights reserved.