Organic Matter and Physical Properties of Postagrogenic Eroded Soddy-Podzolic Soil and Arable Soddy-Podzolic Soil

In a moderately eroded regraded deep-podzolic clay loamy agrosoddy-podzolic soil (Albic Retisol (Loamic)) of unmanaged fallow in Moscow oblast, a significant increase in the content and reserves of total carbon has taken place after 22 years of its fallowing in comparison with the arable analogue. This increase has mainly been due to the rise in the carbon content of easily degradable organic matter (light fraction). The carbon content in the water-extractable organic matter from the fallow soil is also higher than that in the arable soil. The increase in the content of these groups of labile organic substances is apparently due to the amount and composition of plant residues entering the fallow soil, as well as a decrease in their mineralization compared to the arable soil. A significant increase in the content of the light fraction in the lower part of the arable field relative to its upper part has been found, which is associated with the transfer of light particles as a result of water erosion. In the fallow field, these differences are minimal. There has been a downtrend of the bulk and solid phase densities in the layer of 0–10 cm of fallow soil compared to arable soil due to the accumulation of plant residues in this layer. The fallow soil is characterized by a high content of agronomically valuable aggregates of 0.25–10 mm in size, water-stable aggregates, and large (>0.05 mm in size) microaggregates.