POTATO YIELDS AND CADMIUM, NICKEL AND ZIN C CONTENTS IN TUBERS

Yields and Cd, Ni and Zn contents in tubers of four very early potato varieties (Impala, Ukama, Krystala and Koruna) are presented in the co ntribution. Exact field trials were established in two different produ ction regions (Zabcice u Brna - 184 m of altitude and Valecov u Havlic kova Brodu - 460 m of altitude) in the years 1994 to 1996. Regarding t he yields, at both sites and in all experimental years the Holland var iety Impale was found to be the best with the yields at Zabcice 33.54 to 50.59 t.ha(-1), at Valecov 33.36 to 51.09 t.ha(-1). The yields of o ther crops were lower by 6 to 35%. Of the Czech varieties the best was found to be the Variety Krystala at Zabcice (26.04 to 47.71 t.ha(-1)) and the variety Koruna at Valecov (23.15 to 38.52 t.ha(-1)). The lowe st yield was obtained by the variety Koruna (Zabcice) and Ukama (Valec ov). The differences in the Cd content between varieties were signific ant. More Cd was cumulated by varieties Krystala and Koruna. Significa ntly highest Cd concentration (0.024 mg.kg(-1)) was measured in the va riety Krystala. Increased N rate from 60 to 120 kg.ha(-1) increased Cd concentration in tubers by 22%. Higher Cd content was found in tubers at Zabcice (on average 0.023 mg.kg(-1)) and lower at Valecov (0.016 m g.kg(-1)). Tubers in 1996 were marked by significantly lower Cd conten t (0.015 mg.kg(-1)). Ni content in potato tubers at both sites in the whole experimental period in all varieties was below the limit 0.5 mg. kg(-1) of fresh tubers. The variety Koruna was distinguished by the hi ghest Ni content (0.130 mg.kg(-1)). N fertilization also in the case o f Ni was significantly supported its uptake, that is without danger of exceeding of the hygienic standard (increase from 0.094 to 0.109 mg.k g(-1)). in the years 1994 and 1995 three to five times lower Ni concen trations were found at Valecov compared with Zabcice, in 1996 this was only two times lower. Zn contents reached approximately one third to one fourth of the permitted limit of 10 mg.kg(-1). Significant differe nce was found between the varieties Krystala x Impala and Koruna. Othe r relationships and dependences are similar like in the case of Cd and Ni. Zn concentration increased significantly with N rate. Significant difference was also between sites - lower Zn content in tubers from V alecov. In the years 1996 significantly lower Zn concentrations were c haracteristic than in the years 1994 to 1995.