Postagrogenic Changes in the Enzyme Activity and Organic Carbon Content in Chernozem during the First Three Years of Fallow Regime

Comprehensive studies of the biological status of ordinary chernozem (Haplic Chernozem (Loamic)) were carried out in the early years of the fallow regime in comparison with its arable analogue, old fallow, and the reference virgin steppe soils. They included a field experiment on the conversion of an old-arable plot with the ordinary chernozem in Botanical Garden of the Southern Federal University to a fallow. In this experiment, organic carbon and the activity of two classes of enzymes, oxidoreductases (catalases and dehydrogenases) and hydrolases (β-fructofuranosidase) were compared for soils under land-use variants. The organic carbon content in the soil of the young fallow increased already in the first year; it did not change significantly in subsequent years of plant cover restoration, and varied depending on the observation period during the growing season. The activity of the enzymes also increased in the first year of the fallow regime and continued to restore throughout the time after the cessation of agricultural use. The catalase activity in the young fallow soil was 9% higher (p < 0.05) than in the first year of research, the activity of dehydrogenases increased by 20% (p < 0.05), and β-fructofuranosidase by 10% (p < 0.05). However, the enzymatic activity was significantly lower than in the case of old fallow and, especially, of the reference soil in the virgin steppe.