The relationship of soil sulfur with glomalin-related soil protein and humic substances under different mineral and organic fertilisation

Abstract

Recently, the most common avenue of sulfur inputs into the soil has diminished. This was caused by the desulfurisation of the industry in the 80s and 90s, which reduced the sulfite oxide emissions into the atmosphere and, conversely, decreased the deposition of sulfur (S) into the soil (Lehmann et al. 2008). The European Environmental Agency reported a decrease in emissions of sulfur-containing compounds by 74% from 1990 to 2011 (EEA 2015). Sulfur is present in the soil in mineral form, generally representing around 5-10% of total sulfur (S T ) (Kulhánek et al. 2018). Water-extractable sulfur (S H 2 O ) represents around 1% of S T . The rest is distributed among adsorbed (S ADS ) and co-precipitated sulfur occluded in calcium and magnesium carbonate precipitates (Tisdale et al. 1993, McLaren andCameron 1996) that are not available to plants yet can be released (Morche 2008). The remaining 90% to 95% of sulfur is organically bounded, which is also inaccessible to plants but can also be released throughout vegetation (Boye et al. 2010). This is why the organic-bound sulfur needs to be studied closely (Scherer 2009).Soil organic matter (SOM) is a complicated mixture of substances. The fractionation of carbon in SOM (C SOM ) into the fulvic acids (FA), humic acids (HA), and humic substances (HS) categories by their solubility in acids and bases (Fan et al. 2018) is one of the possible approaches to focus the debate about SOM. Together, these can make up between 20% and 80% of C SOM and can be mineralised (Parsons 1989