SEASONAL CHANGES OF SELENIUM AND SELECTED OXIDOREDUCTASES IN SOIL UNDER DIFFERENT FERTILIZATION AND CROP ROTATION SEZONOWE ZMIANY ZAWARTOŒCI SELENU I AKTYWNOŒCI WYBRANYCH OKSYDOREDUKTAZ W GLEBIE O ZRÓ¯NICOWANYM NAWOENIU I ZMIANOWANIU

The objective of the study was to evaluate effects of different doses of FYM and nitrogen on the total selenium content in soil from different crop rotation systems. The aim of the study was to determine the changes of some oxidoreductases activity and Se concentration in soil in relation to applied doses of fertilizers over vegetation period. The experiment was carried out with the crop rotation systems - depleting and enriching in organic matter. The soil was fertilized with manure under potato in the doses of 0, 20, 40, 60 and 80 Mg/ha and with nitrogen in the doses of 0, 40, 80 and 120 kgN ha -1 under winter wheat. The content of total selenium in the investigated soil was in the range of 0.092 to 0.264 mg kg -1 . From the comparison of the results reported in literature one can observe that the studied soil was poor in selenium. Over the investigated period manuring resulted in an increase of total selenium content in soil and for that reason the FYM application can be recommended as a source of selenium in Se-deficient soils. Fertilization with manure resulted in an increase of dehydrogenases and catalase activities in soil with increasing doses of FYM. The selenium content, as well as DHA and CAT activities demonstrated clear seasonal variations. The present studies indicated a significant relationship between activity of soil enzymes, and the organic matter content, affecting the selenium status in soil and plants.