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Peroxide oxidation of clay‐associated organic matter in a cultivation chronosequence
Author(s) -
Plante A. F.,
Chenu C.,
Balabane M.,
Mariotti A.,
Righi D.
Publication year - 2004
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2004.00626.x
Subject(s) - organic matter , soil water , environmental chemistry , peroxide , chronosequence , total organic carbon , hydrogen peroxide , chemistry , soil organic matter , dissolved organic carbon , soil carbon , soil science , environmental science , organic chemistry
Summary Current models of soil organic carbon (SOC) include a passive pool representing refractory soil organic matter (RSOM) with turnover times of hundreds to thousands of years. These models suggest that, as total soil C is depleted, it becomes proportionally enriched in RSOM. The objectives of our study were to quantify clay‐associated organic matter resistant to peroxide treatment in soils presumed to have differing proportions of RSOM, hypothesizing that peroxide‐resistant C in the clay fraction belongs to RSOM, and that its proportion will increase with total C depletion. Clay fractions (< 2 µm) from three soils from a cultivation sequence, differing in the duration of cultivation, one long‐term cultivated soil and one long‐term bare fallow soil corresponded to samples increasingly depleted in total organic C. Samples were suspended in 30% hydrogen peroxide and treated until no changes in C concentration were observed. Total C in the clay‐peroxide suspensions decreased exponentially and displayed kinetics corresponding to labile, intermediate and peroxide‐resistant pools. Carbon isotope analyses showed an enrichment of 13 C in samples after peroxide treatment, compared with before, that decreased from 8‰ in forest samples to 0‰ in long‐term bare fallow. The proportion of peroxide‐resistant C did not differ between soils and represented 12% of initial clay‐associated organic C. No proportional increase with soil C depletion was observed and when expressed on a whole‐soil basis, the results underestimated proposed values for the RSOM pool, suggesting that peroxide treatment may not be appropriate for the estimation of the RSOM pool.