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Decomposition Rate Constants of Size and Density Fractions of Soil Organic Matter
Author(s) -
Hassink Jan
Publication year - 1995
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1995.03615995005900060018x
Subject(s) - organic matter , decomposition , chemistry , soil texture , soil organic matter , bulk density , reaction rate constant , particle size , environmental chemistry , soil water , soil science , kinetics , environmental science , organic chemistry , physics , quantum mechanics
One of the main drawbacks of models describing soil organic matter turnover is that most pools cannot be experimentally identified. The aim of this study was to define meaningful soil organic matter fractions that can be physically isolated and to determine their decomposition rate constants so that they can be incorporated into models. This would be a major step toward verification of models. In this study, soil organic matter was separated into five fractions: the light (density <1.13 g cm −3 ), intermediate (density 1.13–1.37 g cm −3 ), and heavy (density >1.37 g cm −3 ) fractions of macroorganic matter (>150 µm) and the microaggregate fractions with particle sizes between 20 and 150 µm and smaller than 20 µm. The decomposition rate constants of the fractions decreased in the order light, intermediate, and heavy macroorganic matter (23.9, 9.8, and 3.9 × 10 −4 d −1 , respectively) and were lowest for C in the microaggregate fractions <20 and 20 to 50 µm (0.5–0.7 × 10 −4 d −1 ). Since the rate constants of the fractions seemed not to depend on soil texture, they can probably be applied widely. We propose to use these fractions as the principal pools in future soil organic matter models.