Heterogeneity of Organic Matter of Aggregates of Protocalcic Chernozems.

Layers were step-by-step removed from macroaggregates (2–1 mm in diameter) of Protocalcic Chernozems via successive abrasion in a revolving rotator during 5, 10, 15, and 39 h. During processing, the aggregates were divided into fractions with sizes of >1, 1–0.5, 0.5–0.25 and <0.25 mm. The carbon and nitrogen contents were determined in the obtained structural units, and the molecular structure of organic matter was evaluated by the method of analytical pyrolysis with gas chromatographic separation of products and mass detection. In this study, samples of permanent tilled fallow and 17-year-old unmanaged fallow after the permanent tilled fallow were used. It is shown that the particles obtained by abrasion with size of <0.25 mm belong to the peripheral part of the aggregates. They contain significantly less carbon and nitrogen compared to the inner part of the aggregates—structural units of >0.5 mm in size and processed on the rotator for at least 10 hours. The described dependence is observed both for aggregates of tilled fallow and unmanaged fallow. In addition, for the aggregates of the unmanaged fallow, clear differences in the molecular composition organic matter of the peripheral part from the inner part of the aggregates are shown. [ABSTRACT FROM AUTHOR]