Physical and chemical protection of soil organic carbon in three agricultural soils with different contents of calcium carbonate

Clough, A. and Skjemstad, J. O. (2000) Physical and chemical protection of soil organic carbon in three agricultural soils with different contents of calcium carbonate. Australian Journal of Soil Research, 38 5: 1005-1016. doi:10.1071/SR99102


Author Clough, A.
Skjemstad, J. O.
Title Physical and chemical protection of soil organic carbon in three agricultural soils with different contents of calcium carbonate
Journal name Australian Journal of Soil Research   Check publisher's open access policy
ISSN 0004-9573
Publication date 2000-01-01
Sub-type Article (original research)
DOI 10.1071/SR99102
Volume 38
Issue 5
Start page 1005
End page 1016
Total pages 12
Editor J. Fegent
S. Benerjee
Place of publication Collingwood
Publisher CSIRO
Collection year 2000
Language eng
Subject C1
300103 Soil Chemistry
620100 Field Crops
0799 Other Agricultural and Veterinary Sciences
Abstract The amount of organic carbon physically protected by entrapment within aggregates and through polyvalent cation-organic matter bridging was determined on non-calcareous and calcareous soils. The composition of organic carbon in whole soils and <53 m soil fractions was determined by C-13 NMR analysis. High energy photo-oxidation was carried out on <53 m fractions and results from the NMR spectra showed 17-40% of organic carbon was in a condensed aromatic form, most likely charcoal (char). The concept that organic material remaining after photo-oxidation may be physically protected within aggregates was investigated by treating soils with a mild acid prior to photo-oxidation. More organic material was protected in the calcareous than the non-calcareous soils, regardless of whether the calcium occurred naturally or was an amendment. Acid treatment indicated that the presence of exchangeable calcium reduced losses of organic material upon photo-oxidation by about 7% due to calcium bridging. These results have implications for N fertiliser recommendations based upon organic carbon content. Firstly, calcium does not impact upon degradability of organic material to an extent likely to affect N fertiliser recommendations. Secondly, standard assessment techniques overestimate active organic carbon content in soils with high char content.
Keyword Agriculture, Soil Science
Charcoal
Photo-oxidation
Cp/mas C-13 Nmr
Aggregate Stability
Caso4.2h2o
Caco3
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Agriculture and Food Sciences
 
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Created: Tue, 10 Jun 2008, 23:02:56 EST