Enzyme diagnostics for evaluation of effect of nitrogen fertilizers on mineralization and humification processes in sod-podzolic soils

Ecological management of soil resources is an urgent task involving periodic assessment of effect of fertilizers and other anthropogenic factors on the rate and direction of organic matter transformation. Mineralization and humification of organic residues are the most important functions of the soil, which determine its fertility and are closely related to the biochemical activity of microbial communities. When using intensive agricultural technologies, it is required to timely identify potential risks of reducing soil fertility. Taking into account the biochemical nature of the processes of mineralization and humification of organic substances, it is advisable to use indicators of enzymatic activity for this purpose. Enzymes are the most important metabolites of microorganisms. When choosing enzymatic indicators for a reliable assessment of influence of natural and anthropogenic factors on the activity of mineralization and humification, we took into account large-scale and universal processes in the cycles of the main biogenic elements – carbon and nitrogen. Soil enzyme diagnostics was shown to be likely useful instrument for evaluation of natural and anthropogenic factors effect on mineralization and humification processes in sod-podzolic soils. The most informative enzymatic tests for characterization of soil biochemical status in C and N cycles were determined. Biochemical coefficient was proposed as a resulting criteria for interpretation of enzymes activity data, allowing to compare humification and mineralization activities, reveal their disbalance and control of anthropogenic impact on soils. Experimental data on the effect of nitrogen fertilizers on the activity and ratio of humification and mineralization, obtained in long-term field experiments on soddy-podzolic soils of different granulometric composition and level of fertility are presented.