Abstract: Changes in the macro-, meso-, and micromorphological properties of plowed migration-mycelial chernozems (Haplic Chernozems) after their conversion into permanent unmanaged fallow state are discussed. The research objects are located in Kursk oblast. The results of the study indicate that changes in the soil morphology are most pronounced in the plow and carbonate-accumulative horizons. As a result of self-restoration processes, the structure of plow horizons improves, and their color becomes darker. Cracks formed as a result of seasonal soil drying disappear, and the structural degradation of plowed soils is stopped. Hard carbonate nodules formed in deep horizons of plowed soils due to seepage and stagnation of moisture in cracks in the periods of bare land disappear over 25–50 years of fallowing. Transitional forms—relatively soft calcareous nodules (beloglazka, white eyes) with a hard core—may be formed. Upon the uptake of soil solutions by roots, the accumulation of carbonates in the form of fibrous calcite takes place in the humus-containing material around the roots. Carbonate incrustations consisting of fibrous calcite are seen along cracks in plowed soils and in young fallows and are thin and fragmentary in the soils of old fallows and in virgin chernozem. The results of the studies of chronosequences of fallowed soils in Belgorod, Rostov, Lipetsk, and Kursk oblasts are generalized. The main features of transformation of the carbonate status of fallow soils are specified: (a) disappearance of hard carbonate pedofeatures in the lower soil horizons, (b) lowering of the lines of effervescence, and (c) a general decrease in the content and total pool of carbonate carbon. The change in the humus state of fallowed soils after the end of plowing are differently directed: the content of stock of humus decrease in gray soils (Phaeozems) and increase in chernozems and dark gray soils.