Effect of biochar application on variability of the polyphenoloxidase and peroxidase activity of sod-podzolic soil under low and high fertility

Biochars are considered as an attractive tool in agriculture for carbon sequestration and improvement of soil functions. Biochar addition to soils can raise the pH, increase the organic carbon content, enhance nutrient retention, and increase microbial biomass. The introduction of biochar to different soils is an irreversible action. After entering the soil environment, the so called “aging” of biochar begins, due to the water-physical processes occurring in the soil, e.g., moistening, drying, freezing and thawing. Therefore, it is necessary to understand the directions of various changes occurring in the soil when using this ameliorant. The two-year field experiment to study the effect of biochar on the dynamics of some soil enzymes during of biochar aging was performed with the aim to reveal mechanisms of interaction between soil and biochar and to justify the sensitiveness of enzymes on a biochar amendment to the soil. The studied loamy sand Spodosol soil had medium and high soil quality. The experimental design included the soil (control) and the soil with 20 t/ha biochar introduced in the top arable layer (0-10 cm) of 4 m2 plots in 3 replicates. The impact of birch ( Betula spp.) biochar produced by fast pyrolysis at 600 °C was studied. Chemical characteristics of the biochar were as follows: Corg. - 88.9 %, Ntot. - 0.43 %, H - 3.2%, O - 5.1 %, pHН2О 8.3, water content - 3.1 %, ash content - 1.8 %. In 2019, a seed mixture of oat ( Avеna satíva L.) cv. Borrus and common vetch ( Vicia sativa L.) L’govskii cv. was cultivated on the plots at the rate of 200 kg/ha (or 85 g per 4 m2). In 2020, white lupine ( Lupinus albus L.) cv. Dega was cultivated as green manure for winter wheat at the rate of 200 kg/ha. Soil and biochar samples were collected from a 0-10 cm layer of the humus horizon in May to August (at 14-day intervals) with an Endelman soil drill (Royal Eijkelkamp B.V., the Netherlands). The activity of peroxidase (EC 1.11.1.7) and polyphenoloxidase (EC 1.10.3.1) was assessed by the photocolorimetric method (λ = 440 nm and λ = 590 nm, respectively), and the assessment of temporal changes in the oxidation of the surface of biochar was studied by IR spectrometry (an FSM 2202 Michelson spectrometer, Infraspek, Russia). The biochar was found to increase the activity of the studied enzymes, on average by 12-13 %, as compared to the activity in soils without biochar. The peroxidase activity was on average 1.5 times higher than that of the polyphenoloxidase and significantly (p function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }