IRON, MANGANESE AND COPPER CONTENT IN TUB ERS OF VERY EARLY POTATO VARIETIES

The contribution presents the contents of iron, manganese and copper i n tubers of four very early potato varieties (Impala, Ukama, Krystala, and Koruna). The results were obtained in exact field trials in two d ifferent production regions (Zabcice u Brna - 184 m above sea level an d Valecov u Havlickova Brodu - 460 m above sea level) in the years 199 4 to 1996. Differences in iron content were statistically significant. The highest iron content was recorded in tubers of the Ukama variety (3.76 mg.kg(-1)), the lowest one was in the Impala variety (3.15 mg.kg (-1)). Increase of nitrogen dose from 60 to 120 kg.ha(-1) decreased th e concentration of iron in tubers by 0.2 mg.kg(-1) (6%). The effect of a site was not manifested. Tubers were marked significantly by the hi ghest iron content in 1996 (3.72 mg.kg(-1)). Holland varieties cumulat ed significantly less manganese (Impala 0.71 mg.kg(-1), Ukama 0.78 mg. kg(-1)) compared with the Czech varieties (Krystala 0.86 mg.kg(-1), Ko runa 0.81 mg.kg(-1)). The dependence of manganese content on the nitro gen dose was not confirmed. Significant difference was found among sit es where at Valecov concentrations were lower by 25%. The highest mang anese content had tubers in 1995 (0.96 mg.kg(-1)), while the lowest on e was in 1996 (0.56 mg.kg(-1)). Copper contents did not reach in any c ase the permitted limit. At the same time, Holland varieties were mark ed by higher concentrations (Impala 1.06 mg.kg(-1) and Ukama 1.12 mg.k g(-1)). When copper was taken, synergic influence of nitrogen was mani fested. At Zabcice site average copper content was 1.41 mg.kg(-1), at Valecov it was lower by 52.5% (0.67 mg.kg(-1)). In all varieties the s ignificant influence of a year was recorded. Tubers in the year 1994 w ere marked by the highest copper content (1.24 mg.kg(-1)).