The focus of the dissertation thesis called "The use of urea with urease inhibitor in the fertilisation of potatoes" was on the effect of nitrogenous fertilisation with urea and urea with urease inhibitor NBPT (urea stabil) on changes in the content of Nmin in the soil and in nutrients available post-harvest, tuber yields, starch content, macro-elements N, P, K, Ca, Mg and Cd in tubers and tops, content of essential and non-essential amino acids in tubers. To complete the experiment we established a pot trial without the plant where we monitored in regular intervals for 24 days the effect of urea, urea with urease inhibitor (urea stabil) and ammonium nitrate with limestone on changes of the content of Nmin and on the individual forms of nitrogen in the soil. The field trial was conducted at the School Farm in Žabčice (south Moravia; maize-growing region) with potato varieties Karin and Red Anna. The trial involved 7 fertilisation treatments: 1) 100 % urea; 2) 80 % urea; 3) 60 % urea; 4) 100 % urea stabil; 5) 80 % urea stabil; 6) 60 % urea stabil; 7) unfertilised mineral treatment (control). A pot trial was established in the laboratory of Mendel University in Brno using 4 treatments of fertilisation: 1) unfertilised (control); 2) ammonium nitrate with limestone - LAV; 3) urea; 4) urea stabil.