Differences in soil sulfur fractions due to limitation of atmospheric deposition

Abstract

The aim of this work was to estimate the changes in contents of different sulfur (S) fractions in soils under conditions of lowering inputs of S from emissions together with the influence of application of manure and mineral fertilizers. Soil samples from long-term field experiments were used for this purpose. The samples were taken from 10 sites from precise long-term field experiments with different soil-climatic conditions in the Czech Republic. The samples were analyzed using the following fractionation: (i) water soluble S (H<sub>2</sub>O extracts), (ii) sorbed S (0.032M NaH<sub>2</sub>PO<sub>4</sub> extracts) and (iii) S occluded with carbonates (1M HCl extract). Furthermore, the concentration of total S (S<sub>tot</sub>) and organic S (S<sub>org</sub>) was determined. Soil samples were taken in the years 1981 and 2007. During 26 years a decrease of S<sub>tot</sub> by about 3–8%, water soluble S by 65–68% and sorbed S by 39–44% were observed in the topsoil of the evaluated soils. Furthermore, a low increase in the content of organic S was observed. The estimated ratio of S<sub>org</sub> reached 78.7–80.9% from S<sub>tot</sub> in the year 1981 and 87.7–89.8% in 2007. Farmyard manure (40 t/ha) applied every 4 years did not have a significant influence on S fractions and S<sub>tot</sub> contents in soils; intensive S fertilizing increased S<sub>tot</sub> and mobile S forms contents in soils. Very close correlations were obtained especially between S<sub>tot</sub> and water soluble S and organic S.