Crude protein content in dry matter of processing potato tubers cultivated in the Czech Republic in 2004-2005 on three sites with different altitudes and two variants of N fertilization ranged from 5.86 to 11.16%. Differences in crude protein content between doses of 100 kg N ha-1 and 200 kg N ha-1 were significant (P<0.05), resulted at average in 7.5 and 8.4% of dry matter of potato tubers, respectively. The variability of crude protein content was above all
affected by cultivar (34.3%). The yield of crude protein per area unit ranged from 426 to 1279 kg ha-1 and was affected mainly by the year (24.1%) and by interaction of the year and the site (41.5%). The increasing altitude caused at average increasing of tuber yield and consequently increasing of crude protein yield per area unit. However, crude protein content showed opposite trend and the lowest concentration (7.5%) was achieved on the site with the highest
altitude.
