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The Nature and Forms of Sulfur in Organic Matter Fractions of Soils Selected Along an Environmental Gradient
Author(s) -
Bettany J. R.,
Stewart J. W. B.,
Saggar S.
Publication year - 1979
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/sssaj1979.03615995004300050034x
Subject(s) - humin , humus , chemistry , humic acid , soil water , organic matter , fulvic acid , extraction (chemistry) , environmental chemistry , sulfur , soil science , chromatography , organic chemistry , geology , fertilizer
The role of S in humus formation and transformation was hypothesized on the basis of C/N/S ratio and percent HI‐reducible S determinations on organic fractions obtained from soil Ap horizons by a 0.1 M NaOH − 0.1 M Na 4 P 2 O 7 (pH 13.0) extraction‐separation technique. Differences in C/N/S ratios of the conventional humic acid (HA‐A) fractions were greater (from 113:10.6:1 to 270:23.3:1) than those of the total soil organic matter (61:6.5:1 to 112:9.7:1) in soils along an environmental gradient delineated by semiarid Chernozemic Brown to sumhumid Luvisolic Gray soils. This fraction (HA‐A) is thought to represent the end product of the humification process. Differences in C/N/S ratios of conventional fulvic acid (FA‐A), clay associated humic acid (HA‐B) and <2 µm humin were smaller than for HA‐A along the gradient. On the basis of C/N/S ratios and the average percentage of HI‐reducible S in each fraction, e.g. HA‐A, 26%; HA‐B, 44%; FA‐A, 82%; and <2 µm humin, 52%; it was postulated that FA‐A, HA‐B, and <2 µm humin contained the majority of potentially labile S.