ИСТИНА

The composition and structure of aggregates from different agrogenic soils in the southern steppe zone of European Russia have been studied. It is shown that the multi-level study (from the macro- to microlevel) of these horizons makes it possible to identify soil compaction caused by different macroprocesses of soil formation: solonetz, vertisol, and mechanical (wheel) compaction in the rainfed and irrigated soils. The combined micromorphological (fig.1) and computer microtomographic (fig.2) studies of aggregates of 1–2 and 3–5 mm in diameter from compacted horizons of different soils have been performed for the first time. Additional diagnostic features of negative solonetz- forming processes (low open porosity of aggregates seen on tomograms and filling of a considerable part of the intraped pores with mobile substance) and the vertisol-forming processes (large amount of fine intraaggregate pores seen on tomograms and a virtual absence of humus–clay plasma in the intraped zone)—have been identified. It is shown that the combination of computer microtomographic and micromorphological methods is helpful for studying the pore space of compacted horizons in cultivated soils. It should enable us to make more exact predictions of the rates of degradation processes and undertake adequate mitigation measures. Keywords: chernozems, compaction, computer microtomography, kashtanozems, solonetzization, vertic features