Chemical stabilization of organic carbon pools in particle size fractions in no-till and meadow soils |
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Authors: | K Lorenz R Lal M J Shipitalo |
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Institution: | (1) Carbon Management and Sequestration Center, School of Environment and Natural Resources, The Ohio State University, 2021 Coffey Road, Columbus, OH 43210-1085, USA;(2) USDA-ARS, North Appalachian Experimental Watershed, P.O. Box 488, Coshocton, OH 43812-0488, USA |
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Abstract: | The knowledge about the relevance of physical and chemical fractionation methods to soil organic carbon (SOC) stabilization
mechanisms is fragmentary but needed to manage the SOC pool. Therefore, our objective was to compare the C contents of the
particle size fractions coarse and fine sand, silt, and clay of the two uppermost horizons of a soil under three different
management systems (meadow; no-till corn, NT; no-till corn with manure, NTm). The mineral composition was dominated by silt
(48–60%). However, coarse sand and clay showed the highest enrichment of C compared to the bulk soil. In spite of an enrichment
factor below 1, the high proportion of silt made this fraction the main C store. In the upper 30 cm, this fraction amounted
to 27.1 Mg C ha−1 in NTm and progressively less in NT (15.5 Mg C ha−1), and meadow (14.9 Mg C ha−1), representing 44%, 39%, and 39% of the total SOC pool, respectively. The C in the isolated particle size fractions was further
investigated by an oxidizing treatment with Na2S2O8 and a treatment with HF to solubilize the mineral phases. The pools of oxidizable C were comparable among particle size fractions
and pedons, as indicated by Na2S2O8 treatment. The pools of C preferentially associated with soil minerals were also comparable among pedons, as indicated by
HF treatment. However, NTm stored the largest pool (12.6 Mg ha−1) of mineral-associated C in 0–30 cm depth. The silt-associated and mineral-bound SOC pool in NTm was greater compared to
NT due to increased organic matter (OM) input. Thus, the silt particle size fraction at the North Appalachian Experimental
Watershed (NAEW) has the potential for SOC sequestration by stabilizing OM inputs. Mineralogical and molecular level analyses
on a larger set of fractions obtained from entire rooted soil profiles are required, however, to compare the SOC sequestration
capacity of the land uses. |
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Keywords: | Carbon sequestration Land use and soil management Hydrofluoric acid Disodium peroxodisulfate Combined particle size and chemical fractionation |
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