Assessment of organic matter state and physical properties of postagrogenic sod-podzolic soil and its arable analogue

Abstract

Land is often withdrawn from agriculture for various reasons, about 1/4 of the world’s fallow land is in Russia, mainly in the taiga forest zone. Some changes, determined by a combination of various factors, take place in fallow land. Therefore, in order to determine the expediency or priority of returning fallow land to arable land, it is relevant to assess the main indicators of its fertility. To this end, a comparative study of the organic matter and physical properties of an arable sod-podzolic soil and its post-agricultural analogue, which has been fallow for more than 20 years, was carried out. A reliable increase in the carbon content of the light fraction of organic matter in the 0-10 cm layer of the fallow soil was observed in comparison with the corresponding horizon of the arable analogue. In the 10-20 cm horizon this increase was manifested in the form of a tendency, also the tendency of increase in the content of organic carbon (total humus) in the former arable layer of the fallow soil was manifested. The increase in these indicators of the state of organic matter is apparently due to the increase in the amount of plant residues as a result of the succession of natural herbaceous vegetation compared to the amount of post-harvest residues on arable land. The fallow soil also showed an increase in the number of macroaggregates, agronomically valuable aggregates and the water holding capacity of macroand microaggregates compared to the arable soil. Obviously, such an improvement in the structural condition indicators is related to the increase in humus content and the absence of mechanical tillage, which favours the destruction of aggregates. The fallow soil in comparison with the arable soil had reliably lower density and density of solid phase, which is explained by higher content of light fraction of organic matter in it, as well as better structure. The obtained results allow to assess the nature of changes in fertility indicators of sod-podzolic soil as a result of staying in fallow condition. The indicator of the content of the light fraction of organic matter is an earlier indicator of the recovery of the fallow soil compared to the total carbon content in the soil, which allows to determine the expediency and priority of the return of fallow soils to arable land.