The purpose of research is to study the changes in properties of the Oka – river valley floodplain soils with intensive agriculture. The article is devoted to the complex analysis of saturated alluvial soils of three subtypes in the floodplain upstream the river Oka: agridark humus alluvial (turf saturated), agrihumus-hydrometamorphic alluvial (meadow saturated) and agrohumus gley alluvial (meadow-bog saturated). During the observation period (2002–2014) the negative dynamics of humus content (from 2.9 to 2.4 %) and increase of pH values (from 6.7 to 7.6) were revealed as a result of repeated tillage during the growing period by different tools and, in particular, due to plowdown of carbonates from underlying layers. Morphologically and micromorphologically loss of amorphous (mull) forms of humus in the humus horizon of the studied soils was determined. According to figures obtained by density of ñomposition, density of the solid phase and the water permeability of the upper layers of alluvial meadow arable soils of the central floodplain, differences in the spatial structure of arable land were observed. The characteristics of the soil formed on wet spots with a new kind of profile (Apah – G – plow sole – ABg – B1g'– B2g" – B3g"' – BCgf) are presented. To eliminate wet spots it’s necessary to perform regular chisel plowing in order to fracture the seal subsurface horizons and improve water-physical properties of the upper layers of the soil. During geobotanical studies similarities of digression (on arable land) and demutation (on layland) processes in the structure of floodplain phytocenoses were discovered: on the transitional stages the bio- and structural diversity of soil-cover complexes is increasing; in quasi-equilibrium state geographical and topographical differences between phytocenoses are leveled out. In order to maintain soil fertility it is necessary to introduce crop rotations with a large wedge of grass, to form a water conservation zone in the riverbed floodplain by creating protective forest plantations belt, to use a standardized irrigation on the territory of the floodplain and a cyclical one in areas with wet spots.
Keywords: alluvial soils, intensive technologies, changes in agro and chemical properties, agrophytocenosis, digression changes, demutation changes.
