Bachelor thesis is focused on assessment of humic substances content and quality under compost application. Long-term field experiments were established on Haplic Chernozem (Praha). We evaluated total organic carbon content, humic substances sum, humic and fulvic acids content, ratio HA/Fa, humification degree, nutrients content and absorbance of humic substances in UV-VIS spectral range. One way ANOVA -- analysis was used for statistical assessment of received data. Positive effect of compost on humic substances content and quality and on nutrients content was confirmed.