The Use of Mixtures of Sulfur and Bracken Litter to Reduce pH of Former Arable Soils and Control Ruderal Species

Abstract

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.

Are Sulfurous Soil Amendments (S0, Fe(II)SO4, Fe(III)SO4) an Effective Tool in the Restoration of Heathland and Acidic Grassland after Four Decades of Rock Phosphate Fertilization?

“…Surface soil from the polluted sites had acidified to as low as pH 0.88 in their study. This extreme example demonstrates that with sufficient S 0 , the soils’ natural buffering capacity can be completely overwhelmed, a capacity employed with success to reduce pH in experimental heathland restoration (Chambers et al 1996; Williams et al 1996; Owen et al 1999; Owen & Marrs 2001). These authors used an agricultural chemical (S 0 ) to reverse years pH amelioration in land improved for arable production.…”

“…Incorporation and grain size almost certainly account for the more rapid oxidation of S 0 in the former studies (Chapman 1996). These reach a pH minima within 1 year (Owen et al 1999; Owen & Marrs 2001), whereas, in a separate experiment, the Hartland soils have continued to fall for over 2 years (Tibbett & Diaz, unpublished data).…”

Modifying Soil Chemistry to Enhance Heathland Recreation: A Use for Sulphur Captured During Oil Refining

“…increased soil pH and nutrient availability) so that ericaceous species are not out-competed by mesotrophic grasses [11,12]. This can be achieved by physically removing the improved topsoil [13,14] or by chemically amending it to reduce pH and macronutrient concentrations [15,16]. Usually only one of these approaches is used and the acidification agent that has emerged as particularly effective is elemental sulphur in the form of the agricultural fertiliser Brimstone 90 [17,18].…”

Land‐use legacy and the persistence of invasiveAvena barbataon abandoned farmland

“…Where the persistence of an exotic species is contingent on elevated soil fertility, the effort required to shift the community away from the invader-dominated state can be substantial. It can take years of intensive management to restore natural fertility to old-fields (Berendse et al 1992;Marrs 1993;Walker et al 2004) and such efforts are usually too costly to implement at the landscape scale (Owen & Marrs 2001;Pywell et al 2007). Where invader persistence is likely regardless of soil fertility, efforts might instead be directed towards the removal or depletion of the exotic species and supplementing the supply of native species.…”