The humus status of cultivated soddy-podzolic soils of Northwestern Russiaand its transformation under modern conditions

The humus status of most of the cultivated soddy-podzolic soils in Northwes tern Russia is unsatisfactory. It approaches the optimal level by the main parameters only at the stage of good cultivation. The calcareousness of par ent materials is an additional optimizing factor. The use of mineral fertil izing systems on well cultivated soils results in quite a rapid degradation of their humus status, while it ensures the maintenance of the initial par ameters of weakly cultivated soils.