Melinda Molnárová

Biochar has been widely recognized for its potential to improve soil quality and mitigate greenhouse gas (GHG) emissions. A field experiment was conducted in a temperate climate zone of Slovakia on Haplic Luvisol and evaluated the long-term impact of biochar on soil properties, nitrous oxide (N₂O) emissions, and winter wheat (Triticum aestivum L.) yield. Biochar was applied in 2014 at rates of 0, 10, and 20 t ha⁻¹ and reapplied in 2018 at the same rates, combined with nitrogen (N) fertilization (0, 140, and 210 kg N ha⁻¹). Measurements, conducted from March to October 2021, showed that biochar improved soil water content, increased soil pH, and enhanced soil organic carbon content. However, the concentrations of NH₄⁺-N and NO₃⁻-N generally decreased across all the treatments compared to their respective controls. Biochar reapplication rate at 20 t ha⁻¹, especially combined with second level of N-fertilization, led to a significant reduction in cumulative N₂O emissions by 38.40%. Winter wheat yield was positively correlated with both biochar application (10 and 20 t ha⁻¹) and N levels (140 and 210 kg N ha⁻¹), but these differences were not statistically significant (p > 0.05). The positive effects of biochar on soil properties and yield declined over time, with no significant yield differences observed 7 years after the initial application and 3 years after reapplication. These findings suggest that while biochar can enhance soil conditions and reduce GHG emissions in the short term, its long-term effectiveness remains uncertain. Further research is needed to explore alternative biochar feedstocks, application methods, and strategies to sustain its benefits in agricultural systems.

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 CO ₂ 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 4 ⁺ ) and nitrate (NO ₃ ^- ) 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 CO ₂ emissions and cumulative CO ₂ emissions during the study period (April – October) in 2022 compared to the control without biochar application.