Effect of conditions of locality, variety and fertilization on the content of ascorbic acid in potato tubers

The effect of conditions of locality, variety and fertilization on ascorbic acid (AA) content in potato tubers was in vestigated in precise field trials in 2004 and 2005 in the Czech Republic. From four localities and in the two-year average the highest AA was statistically determined in the locality of Přerov nad Labem with the highest average temperature values during both experimental years (by 6.7 to 11.5% higher in comparison to other localities). Similarly, the effect of variety was also very significant; Marabel variety had the highest AA content (207.2 mg/kg fw) and exceeded other seven varieties by 15–49%. A negative effect on AA content in tubers was observed in the case of an increased intensity of N fertilization (at 180 kg N/ha AA decrease was lower by 6.1% compared to doses 100 kg N/ha). On the contrary, a favourable effect was determined at increased levels of potassium and magnesium fertilization (at 166 kg K/ha and 60 kg Mg/ha AA increase was by 6.2% higher compared to the levels of 108 kg K/ha and 30 kg Mg/ha).