Abstract
The effect of N, P and K application on the grain yield of spring barley in 2005-2008 within three long-term field experiments (Čáslav, Ivanovice, Lukavec) was evaluated. In these experiments, nitrogen at rates of 50, 77.6, 105 and 132.5 kg N ha-1, phosphorus at rates of 14 and 29.4 kg P ha-1 and potassium at 59 and 96.4 kg K ha-1 was annually applied to the treat-ments during that period. Four years summarizing shows that the optimal application rate of fertilizers resulting in a grain yield above 6 t ha-1 was 105 kg N ha-1, 14 kg P ha-1 and 96.4 kg K ha-1 in Čáslav and above 7 t ha-1 was 78 kg N ha-1, 14 kg P ha-1 and 59 kg K ha-1 in Ivanovice. The rate of N 132.5 kg ha-1 in Lukavec increased the grain yield more than three-fold (from 1.94 to 6.12 t ha-1) and probably was not sufficient to obtain the highest grain yield in this locality. No significant difference was recorded between grain yields in P and K fertilizing treatments in any of the three stations. The key result is that degraded chernozem (in Ivanovice) and greyic phaeozem (in Čáslav) demonstrate a high and long-term stable natural fertility, but yields of spring barley of low productive sandy-loamy Cambisol is strongly affected by high rates of nitrogen application.