Influence of Different Types of Land Use on Prokaryotic Communities and Organic Matter Stabilization in Soddy-Podzolic Soil

Abstract

The influence of crop rotation with different saturation with legumes and continuous grain crops (winter rye and spring barley) on the structure of prokaryotic communities and preservation of soil organic matter has been studied in a long-term stationary experiment (1977–2018) on a soddy-podzolic soil (Eutric Albic Retisol (Abruptic, Loamic, Cutanic)) of Perm oblast. Permanent black fallow and unmanaged fallow were used as reference standards. Minimum values of the coefficients of mineralization (0.37) and pedotrophicity (0.28) calculated on the basis of direct counting of microbial colonies cultivated on standard nutrient media (MPA, SAA, and SA) have been found in the unmanaged fallow soil, and maximum values of these coefficients (1.97 and 1.30, respectively) were found in the black fallow soil. Inverse relationships were found between the Corg content in the soil and the mineralization coefficient (r = –0.67; p crop rotation (0–28.6–42.9% of legumes) > continuous grain crop > permanent black fallow, In the cultivated and black fallow soils, along with general decrease in the organic matte stock, its lability increased as evidenced by the Cha : Cfa ratio (0.55–0.79), which were lower than in the unmanaged fallow soil (0.96). The closest negative correlation (r = –0.81; p < 0.001) was observed between the mineralization coefficient and the Cha : Cfa ratio. It has been also shown that different uses of soddy-podzolic soil were accompanied by structural rearrangements of the actinomycetal complex selected as a model group of soil microorganisms. In particular, regular mechanical tillage and application of mineral fertilizers (N60P30K60) contributed to an increase in the species spectrum of streptomyces, a change in the frequency of occurrence and relative abundance of individual sections and series, and a change in dominant forms. The results of this study demonstrated the possibility of using microbiological indicators as biomarkers of the state of soil organic matter.