Content and changes in dissolved organic matter in meadow and arable soils over time

Considering the discrepancies in the reports on seasonal changes in the content of dissolved organic carbon, this paper concerns the research which aimed at defining the content and seasonal changes in dissolved organic matter (DOM) in arable and meadow soils in moderate climate conditions. The research has involved the soils sampled in the kujawsko-pomorskie province (Poland). Gleic Phaeozems (meadow soils), Brunic Arenosols and Eutric Cambisols were sampled from the depth of 0-30 cm, 30-60 cm and 60-100 cm, November 2011 through September 2013. The soil samples were analyzed for dry weight content, pH, content of total organic carbon and total nitrogen. DOM was extracted with 0.004 mol·dm⁻³ CaCl₂, in the extracts the content of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) were assayed. The share of DOC was determined by the soil management. The analysis of variance did not show significant differences in the content of TOC and Nt across the soil sampling dates. Were recorded changes in DOC and DNt between successive sampling dates; for topsoil for DOC – from -12.06% to 13.34% (meadow soils) and for DNt -40.84% to 47.44% (arable soils).