One-year field experiment with spring barley (Hordeum vulgare L.) was carried out to evaluate the effect of biochar amendment on the pH of Orthic Luvisol at the research site located in western Slovakia (lat. 48° 19′ 00″; lon. 18° 09′ 00″). Biochar with higher pH (8.8) was applied to slightly acidic soils with the initial pH at 5.6. The field experiment consisted of control, 10 and 20 t ha−1 (B0, B10, B20) of biochar application to soils combined with three levels of nitrogen fertilization (0, 40 and 80 kg N ha−1) (N0, N40, N80). The soil pH (KCl) at depth 0–10 cm was measured once a month (March – October, 2014). Application of both biochar rates (10 and 20 t ha−1) increased pH (in all months) with the magnitude of 0.13–1.09 units in all three fertilization levels (0, 40 and 80 kg N ha−1) compared to the control one. However, the significant increase (p <0.05) was found only in the treatment B10N0 (3 of 8 measurement events) and B20N0 (6 of 8 measurements) when no nitrogen was applied and in the treatment B20N80 (5 of 8 measurements) when 80 kg of nitrogen was applied. According to this, the biochar incorporation to soil can be suggested as a possible way to ameliorate soils and may be effective in increasing soil pH.
