| Summary: | One of the challenges of harnessing higher productivity levels and sustainability of agriculture related to N fertilization is in expanding soil N<sub>2</sub>O emissions, which has become a serious issue in recent years. Recent studies suggest that biochar may be the solution to this problem, but there is still a knowledge gap related to biochar application rates and its reapplication in Central Europe; therefore, in this study, we investigated the effect of biochar (initial application and reapplication in 2014 and 2018, respectively, at rates of 0, 10 and 20 t ha<sup>−1</sup>) combined with N-fertilizer (N0—0 kg N ha<sup>−1</sup>; N1—108 kg N ha<sup>−1</sup> and N2—162 kg N ha<sup>−1</sup>) during the growing season of maize in 2019 (warm temperature with normal precipitation) on the changes of soil properties and N<sub>2</sub>O emissions in the silty loam, Haplic Luvisol, in the temperate climate of Slovakia. The results showed that the application and reapplication of biochar proved to be an excellent tool for increasing soil pH (in the range 7–13%), soil organic carbon—C<sub>org</sub> (2–212%), and reducing the soil’s NH<sub>4</sub><sup>+</sup> (41–69%); however, there were more pronounced positive effects when biochar was combined with N-fertilizer at the higher level (N2). The same effects were found in the case of N<sub>2</sub>O emissions (reduction in the range 33–83%). Biochar applied without N-fertilizer and combined with the higher fertilizer level had a suppressive effect on N<sub>2</sub>O emissions. Biochar did not have any effect on maize yield in 2019.
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