- Title
- Comparison of structural stability, carbon fractions and chemistry of krasnozem soils from adjacent forest and pasture areas in south-western Victoria
- Creator
- Carter, Martin; Skjemstad, J. O.; MacEwan, Richard
- Date
- 2002
- Type
- Text; Journal article
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/59573
- Identifier
- vital:182
- Identifier
- http://www.publish.csiro.au/?act=view_file&file_id=SR00106.pdf
- Identifier
- http://dx.doi.org/10.1071/sr00106
- Identifier
- ISSN:0004-9573
- Abstract
- Basalt-derived krasnozems are generally well-structured soils; however, there is a concern that intensive agricultural practices may result in an adverse decline in soil organic carbon, organic matter chemistry, and structural quality over time. A study was conducted on loam to silty clay loam krasnozems (Ferrosols) near Ballarat in south-western Victoria to assess changes in soil C, soil structural stability, and C chemistry, at the 0-10 cm soil depth, under 3 paired sites consisting of adjacent long-term forest (Monterey pine or eucalyptus) v. 30 year cropping [3 year pasture-2 year crops (potato and a root crop or grain)]. Soil structural stability was also characterised in the A and B horizons under long-term eucalyptus and several cropped sites. Organic C levels in the A horizons for all the soils were relatively high, ranging from 46 to 89 g/kg. A lower organic C (30%), associated mainly with loss of the sand-sized (> 53 mum) macro-C fraction, and a decrease in exchangeable Ca and Mg was found in the agricultural soils, compared with forest soils. Physically protected C in the <53 μm fraction, as indicated by UV photo-oxidation, was similar among soils. Wet sieving indicated a decline of both C and N concentration in water-stable aggregates and the degree of macro-aggregation under agricultural soils, compared with the forest soils. However, soil structural changes under cropping were mainly related to a decline in the >5 mm sized aggregates, with no deleterious increase in the proportion of 0.10 mm aggregates. Solid state C-13 NMR spectroscopy indicated a decrease in O-alkyl and alkyl C under pasture and cropping compared with forest soils, which was in agreement with the decline in the macro-C fraction. Characterisation of C chemistry following UV photo-oxidation showed that charcoal C (dominant presence of aryl C) accounted for 30% of the total soil organic C, while other functional groups (polysaccharides and alkyl C) were probably protected within micro-aggregates. Based on soil organic C and aggregate stability determinations alone, the implications for soil physical quality, soil loss, and diffuse pollution appear minimal.
- Publisher
- CSIRO
- Relation
- Australian Journal of Soil Research Vol. 40, no. 2 (2002), p. 283-298
- Rights
- Open Access
- Rights
- Copyright CSIRO
- Rights
- This metadata is freely available under a CCO license
- Subject
- 0503 Soil Sciences; Krasnozem; Forests; Carbon fractions
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