Seasonal changes in the content of dissolved organic matter in arable soils

Ewa Rosa,Bozena Debska

doi:10.1007/s11368-017-1797-y

Abstract

PurposeThe aim of this paper has been to determine the seasonal changes in the content of dissolved organic matter (DOM) in the soils under agricultural use based on assaying changes in dissolved organic carbon (DOC) and dissolved nitrogen (DNt) as well as determining the factors which can define the DOM in soils.Materials and methodsThe research has involved the soils under agricultural use sampled in the Kujawsko-Pomorskie province (Poland). Phaeozems and Luvisols were sampled from the depth of 0–30, 30–60, and 60–100 cm, November 2011 through September 2013, in November, March, May, July, and September. The soil samples were assayed for the grain size composition, pH, dry weight content, content of total organic carbon, and total nitrogen. Dissolved organic matter was extracted with 0.004 mol dm3 CaCl2; in the DOM extracts, the content of dissolved organic carbon (DOC) and dissolved nitrogen (DNt) were assayed. The research results were statistically verified.Results and discussionIt has been demonstrated that in the first year of research, the content of dissolved organic carbon in the soils was changing throughout the year. The highest differences in the content of that carbon fraction occurred across the soil sampled in autumn and the soil sampled in spring. In the second year of research, an inverse dependence was noted. DOC was migrating to deeper layers of the soil profile; yet, the migration got more intensive in summer. The content of dissolved nitrogen was not changing significantly throughout the year. Higher DNt content in the surface layer, in general, resulted in a higher content of dissolved nitrogen in deeper profile layer, which could have been due to leaching of the nutrient deep down the soil profile.ConclusionsThe content of dissolved organic carbon was significantly related to the content of total organic carbon and total nitrogen. Significant changes in the content of dissolved forms of nitrogen were reported in the profile of Phaeozems due to mineral fertilization and irrigation. The soils where irrigation and higher nitrogen rates had been applied demonstrated a higher content and share of soluble forms of nitrogen, as compared with the soils non-irrigated and the soils where lower nitrogen rates had been supplied.

Highlights

Dissolved organic matter (DOM) is a heterogeneous phase which includes simple short-chain organic compounds representing a group of non-specific humus substances as well as watersoluble substances, being humus compounds in nature (Moore 2003; Silveira 2005)
The content of dissolved organic carbon was significantly related to the content of total organic carbon and total nitrogen
The content of dissolved organic carbon (DOC) in the soils under agricultural use was changing throughout the year

Summary

Introduction

Dissolved organic matter (DOM) is a heterogeneous phase which includes simple short-chain organic compounds representing a group of non-specific humus substances (fatty acids, organic acids, amino acids, sugars) as well as watersoluble substances, being humus compounds in nature (Moore 2003; Silveira 2005). DOM frequently accounts for less than 1% of the total organic matter, it plays a very important role in biogeochemical cycling of carbon, nitrogen, and phosphorus as well as in nutrients transport. It is a factor stabilizing colloids and soil aggregates. E.g., Zsolnay (1996), Kalbitz et al (2000), Chantigny (2003), as well as Chow et al (2006), the formation and mobility of dissolved organic matter in the soils under agricultural use depends on many environmental factors (climate, hydrological conditions, microbiological activity) and anthropogenic factors (tillage, mineral fertilization, organic fertilization and/or natural fertilization, liming)

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