The effect of different rates of biochar on selected soil properties and enzymatic activity 48, 60, and 72 months after biochar application to soil was investigated. Soil enzymatic activity (dehydrogenase—ADh; phosphatase—Aph; urease—AU), the organic carbon content (TOC), the total nitrogen content (N_t), the mineral nitrogen content (NH₄⁺, NO₃⁻), and soil pH were determined. The study was conducted on Haplic Podzol originating from glaciofluvial fine-grained loamy sand. Biochar was applied to soil under winter rye (Secale cereale L.) at rates of 10 (BC₁₀), 20 (BC₂₀), and 30 t ha⁻¹ (BC₃₀). Plots with biochar-unamended soil were the control treatment (BC₀). The pH, TOC, and N_t content in the biochar-amended soil were higher compared to the control soil. A broader C:N ratio was found in the BC₀ soil compared to BC₁₀, BC₂₀, and BC₃₀. With increasing biochar rate, the content of the ammonium nitrogen form (NH₄⁺) decreased and was statistically lower than in the control soil (BC₀). The soil in the BC₂₀ and BC₃₀ treatments was characterized by the highest content of NO₃^-, whereas the lowest nitrate nitrogen content was found in the control soil (BC₀). Biochar application increased soil enzymatic activity. Dehydrogenase activity increased with increasing biochar rate. As far as phosphatase and urease activity is concerned, a similar relationship was not observed. In this case, the soil amended with biochar at a rate of 20 t ha⁻¹ (BC₂₀) was characterized by the highest phosphatase and urease activity.