Tracking the fate of dung-derived carbohydrates in a temperate grassland soil using compound-specific stable isotope analysis

Jennifer A. J. Dungait, Roland Bol, Ian D. Bull, Richard P. Evershed

Research output: Contribution to journalArticle (Academic Journal)

28 Citations (Scopus)

Abstract

Carbohydrates are major organic components of dung and are likely to contribute substantially to increased carbon stocks in manured soils. To investigate this hypothesis, a field-scale experiment was conducted on a temperate grassland site in Devon, UK. C-4 dung (bulk delta C-13 value -12.6%) was applied to a temperate grassland C-3 soil (bulk delta C-13 value -30.3 parts per thousand) in April and the surface soil beneath cow pats sampled at seven dates over a year. Total carbohydrates were extracted as their monosaccharide components and analysed as the alditol acetates using gas chromatography. The delta C-13 values of the major monosaccharides glucose (-11.5 +/- 0.6 parts per thousand), xylose (-10.4 +/- 0.4 parts per thousand), arabinose (-10.4 +/- 0.5 parts per thousand) and galactose (-8.3 +/- 1.6 parts per thousand) extracted from the C-4 dung via acid hydrolysis were indicative of their source. Their weighted mean delta C-13 value was -10.8 parts per thousand, 1.8 parts per thousand more C-13-enriched than the bulk dung value. The delta C-13 values of individual monosaccharides recovered by acid hydrolysis in the 0-1 cm and 1-5 cm soil horizons beneath C-4 cow pats, compared with control soils determined over 372 days, allowed assessment of the extent of incorporation and fluxes of dung-derived monosaccharides. A maximum of 60% of the dung C in soil was derived from carbohydrates after 56 days, declining to around 20% after 372 days. Incorporation dynamics varied between monosaccharide species. Glucose, xylose and arabinose behaved in a similar manner because of their predominantly plant cell wall derived provenance in the dung, whilst dung-derived galactose and mannose appeared to have a microbial source in the soil. The dynamics of total dung-derived monosaccharides in the top 5 cm was comparable to incorporation and flux of bulk dung C, previously estimated using bulk delta C-13 values. The movement of dung-derived carbohydrates into the soil was inequivalent between the 0-1 cm and 1-5 cm horizons. The lack of a significant difference in concentration, but the evidence for the persistence of dung-derived monosaccharides in soil based on delta C-13 values, indicated replacement of existing pools in the soil, suggesting that the ability of this particular soil to sequester further C derived from carbohydrates was limited. (C) 2009 Published by Elsevier Ltd.

Original languageEnglish
Pages (from-to)1210-1218
Number of pages9
JournalOrganic Geochemistry
Volume40
Issue number12
DOIs
Publication statusPublished - Dec 2009

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