Free and intra-aggregate organic matter as indicators of soil quality change in volcanic soils under contrasting crop rotations

A - Papers appearing in refereed journals

Zagal, E., Cordova, C., Sohi, S. P. and Powlson, D. S. 2013. Free and intra-aggregate organic matter as indicators of soil quality change in volcanic soils under contrasting crop rotations. Soil Use and Management. 29 (4), pp. 531-539.

AuthorsZagal, E., Cordova, C., Sohi, S. P. and Powlson, D. S.
Abstract

Soil physical fractionation techniques may provide indicators of changing soil organic carbon (SOC) content; however, they have not been widely tested on volcanic soils (Andisols). In this study, we assessed two fractions as potential indicators in volcanic soils, using two sites in Chile converted from natural grassland to arable and mixed crop rotations, 8 and 16yr previously. In the 8-yr experiment, SOC had declined under all rotations, with smaller changes where the rotation included 3 or 5yr of perennial pasture. Whereas the average SOC was only 76% of the level in the preceding natural grassland, the corresponding value after 16yr for the second site was 98% (and 93% under continuous arable), probably reflecting its high allophane clay content. The fractionation procedure tested proved applicable to both Andisols, but the intra-aggregate light fraction (IA-SOM, isolated in sodium iodide solution at 1.80g/cm(3) after ultrasonic dispersion) accounted for a very small proportion of total SOC (<1%). We suggest that in Andisols, the free light fraction (FR-SOM, isolated in sodium iodide at solution of the same density, but prior to ultrasonic dispersion) is stabilised to a greater extent than in nonvolcanic soils, and the intra-aggregate fraction plays a more minor role as a pool of intermediate turnover. The relative value of each fraction needs to be confirmed through dynamic experiments, using more sites, and including situations where SOC content is initially low.

KeywordsSoil Science
Year of Publication2013
JournalSoil Use and Management
Journal citation29 (4), pp. 531-539
Digital Object Identifier (DOI)doi:10.1111/sum.12070
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
CONICYT
FONDECYT
Funder project or codeDelivering Sustainable Systems (SS) [ISPG]
Output statusPublished
PublisherWiley
Grant ID1990456
ISSN0266-0032

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