Effects of Biochar on the Agrochemical Indicators and Enzyme Activity of Soils in the Middle Taiga of Karelia

A prolonged impact of the wood biochar applied at a dose of 1.5 kg/m2 on the dynamics of changes and trends in main agrochemical characteristics and enzyme activity in soils of different textures in the middle taiga zone of Karelia has been studied. The plots for 2-year-long monitoring (area, 5 m2) are randomly located (in four replicates) on a cropland with Umbric Podzol and Umbric Retisol-The following parameters are analyzed on a monthly basis during the growing season: pH_H_2O , pHKCl, K2O, P2O5, N– NO₃⁻ , N– NH₄⁺ , Corg, Ntot, and C/N; in addition, bulk density and catalase, invertase, and urease activities are assessed annually. Application of biochar to Umbric Podzol causes a significant increase in pHKCl, K2O, and mineral nitrogen content. Biochar has a considerable effect on the P2O5 content in the first year of observation. A divergent linear trend for pHKCl, K2O, and Corg is observed in the coarse-textured soil, which suggests a considerable aftereffect of the added biochar during the second year of observation. As for Umbric Retisol, biochar has a statistically significant effect only on pH_H_2O . The nitrate nitrogen content considerably decreases in the fine-textured soil against the background of insignificant variation in the content of ammonium nitrogen. The bulk density of soils changes insignificantly. Characteristic of both soils is a statistically significant increase in the Corg content and C/N ratio at a constant Ntot value, which creates the conditions favorable for nitrogen immobilization. Biochar does not influence the urease and catalase activities versus invertase, which responds to a change in carbon content is soils.