Exploring Biochar with N-Fertilizer Effects on Soil CO₂ Emissions and Physical-Chemical Properties as a Climate Change Mitigation Tool

The global agriculture industry is facing never before faced issues in the form of soil degradation, water scarcity, rising greenhouse gas emissions, and climate change. Among the possible remedies, applying biochar to the soil has drawn interest as a viable strategy. Although a great deal of literature has been written about the benefits and drawbacks of applying biochar initially, there is still a significant amount of research on the effects of using biochar repeatedly. This study seeks to address this gap by examining the varied effects of both the initial application (at rates of 0 t.ha⁻¹, 10 t.ha⁻¹, and 20 t.ha⁻¹) and the reapplication of biochar (at rates of 0, 10, and 20 t.ha⁻¹), especially when combined with different levels of nitrogen fertilizer (0, 108, and 162 kg.ha⁻¹). The investigation focuses on soil properties and CO₂ emissions from Haplic Luvisol in the temperate climate zone (Slovakia). The results showed that biochar generally improved soil properties, such as soil pH (KCl) (p <0.05), shifting it from acidic towards moderately acidic, and generally led to a decrease in ammonium (NH₄⁺) and nitrate (NO₃^-) content. The second level of fertilization, combined with different biochar treatments, yielded the most efficient results in physical properties such as soil temperature, bulk density (BD), and soil water content (SWC) compared to control treatments without biochar. Biochar application contributed to the reduction of both average daily CO₂ emissions and cumulative CO₂ emissions during the study period (April – October) in 2022 compared to the control without biochar application.