Metabolome of Typical Chernozems under Different Land Uses

The effect of land use on the formation of the metabolome of typical Chernozem is studied. Typical Chernozems (Haplic Chernozems) of four land uses-55-year-old permanent bare fallow, the plot untilled for 21 years after permanent bare fallow, and 4-year field experiments with zero tillage and traditional tillage-from the long-term field experiments at the Kursk Federal Agricultural Research Center (Cheremushki, Kursk oblast, Russia) are analyzed. To study the soil metabolome, the water extracts of both fumigated and nonfumigated soil samples are assayed for the contents of dissolved organic (DOC) and microbial biomass (C-mic) carbon species using high-temperature catalytic oxidation; the soil metabolites are analyzed using gas chromatography-mass spectrometry. The effect of postagrogenic Chernozem transformation on the accumulation of labile soil carbon species is demonstrated by the case study of the plot untilled for 21 years. Plowing of Chernozems in the absence of plant litter decreases the content of labile carbon. A positive effect of no-till practice on the content of labile carbon species is observable at the level of a trend. According to metabolomic analysis, 21 compounds involved in the metabolism of carbohydrates, lipids, and nitrogenous substances are identified in Chernozems. The Shannon diversity index shows that tillage has a negative effect on the complexity of metabolic profiles in Chernozems. Untilled Chernozems and those under permanent fallow conditions display the most contrasting metabolic compositions with the prevalence of metabolites having plant and microbial origin, respectively. The metabolites of a plant origin tend to accumulate in the chernozem under no-till conditions. The components of the carbohydrate metabolism are prevalent in the metabolomic profile of arable chernozemic soils and the components of nitrogen and lipid metabolism predominate in the untilled soils.