Long‐Term Effects of Land Use and Fertilizer Treatments on Sulfur Cycling

Abstract

AbstractThe unique archived samples from the Rothamsted Broadbalk Experiment, England, were used to evaluate long‐term effects of changing S inputs from atmospheric deposition and fertilization on soil S pools and soil S isotope ratio since 1843. The effects of changing land uses were also investigated. Large S inputs from atmospheric deposition and from sulfate fertilizers did not result in any significant accumulation of soil organic or inorganic S in the arable plots where organic C remained stable. Inputs of sulfate in excess of crop uptake were lost mainly through leaching. Organic S accumulated markedly in the arable plot receiving farmyard manure (FYM) or where arable land was allowed to revert to woodland or grassland. In the latter two systems soil organic C accumulated faster than organic S. In all soils investigated the S isotope ratio (δ34S) decreased substantially during the last 150 yr. The decrease in δ34S was greater in the woodland, grassland, and the arable FYM plot than in other arable plots receiving either inorganic fertilizers only or no fertilizers. The results indicate that atmospheric S was more depleted in 34S than the soil native S at the experimental site, and that atmospheric S was incorporated into the organic pool to varying degrees depending on the C pool. In conclusion, land use had a large effect on the S cycling in soils, which is driven mainly by soil organic C cycling. Without accumulating soil organic C, there appears to be little scope for S retention in temperate soils with neutral pH.