Change in the Soil Complex on Fallow Arable Land of the Boreal Zone of North-West Russia

Abstract

Changes in the agrochemical state of old arable soils on two-membered sediments under the formed mature stands of pine and spruce in the Leningrad region of Russia are considered. It is noted that different pH and organic substances content of soil profile is observed depending on rock composition and granulometric condition of soils. The greatest acidification of all horizons along the soil profile occurs in stands with spruce predominance. At all objects studied the humus content is higher in the horizon of formed forest soil. The largest organic substances stock in the former arable horizon is found in areas dominated by pine. In general, in the investigated sites with spruce and pine stands in the soil complex, the amount of mobile phosphorus (P2O5) decreases as the pH value increases along the genetic horizons. As for mobile forms of potassium (K2O), the dependence of its content reduction on the genetic horizons of the soil in the bottom profile from litter to loamy bedding is observed, where there is some increase in its content. High potassium content in postagrogenous soils under the forest indicates the ability of the soil to keep its level in equilibrium for a long time. The return of the former old arable soils and the native state has not yet happened.