Does Biochar Influence Soil CO₂ Emission Four Years After Its Application to Soil?

Biochar application into soil has potential as a means for reducing soil greenhouse gas emissions and climate mitigation strategy. In this study, we evaluated the impact of two doses of biochar (10 and 20 t.ha⁻¹) applied in 2014, combined with three fertilization levels (N0, N1, N2) on carbon dioxide (CO₂) in field conditions during the growing season (April – October) in 2018. The field site is located in the Nitra region of Slovakia – Malanta. The soil in the field was classified as a silt loam Haplic Luvisol. There was not found any statistically significant (P <0.05) decreasing effect of biochar with or without N-fertilizer after four years of its application on average daily and cumulative CO₂ emissions, while the CO₂ emissions increased with additional N-fertilizer. Biochar decreased (insignificantly) the daily and cumulative CO₂ emissions only in the treatments without N-fertilization and in the treatment fertilized with higher level of biochar application (20 t.ha⁻¹) and N-fertilizer (80 kg.N.ha⁻¹). According to these results it can be concluded that the biochar applied to soil is not able to reduce CO₂ emissions after four years of its application when it is combined with usual agriculture practices which include N-fertilization.