The aim of investigations conducted in the years 2005–2007 was to determine the chemical composition of nutrient solutions in the root environment of tomato grown in wood fiber and rockwool, under the influence of diverse levels of nitrate nitrogen in the nutrient solution amounting 200, 220 and 240 mg N-NO₃·dm^-3. With an increase in nitrate nitrogen content in nutrient solutions used in plant fertigation a significant increase was observed in the contents of N-NO₃ in nutrient solutions of the root environment, collected from wood fiber and rockwool. No such effect was found for contents of N-NH₄, P, K, Ca, Mg, Fe, Mn, Zn, Cu, B, Na, Cl or pH and EC. In case of wood fiber the following nutrient concentration series was found in nutrient solutions of the root environment in relation to the nutrient solution flowing from the drippers: Na > Cu > Ca > Zn > K > Cl > B > N-NO₃; the following were reduced Fe > Mg > P-PO₄ > N-NH₄ > Mn. Nutrients being concentrated in root environment solutions during tomato growing in rockwool were: Na > Ca > Cu > Fe > Cl > K > Zn > B > S-SO₄ > N-NO₃, while contents of Mg > P-PO₄ > N-NH₄ > Mn decreased. Despite of a wide range of carbon to nitrogen ratio (C:N) in wood fiber (123–127), no significant reduction of nitrates was shown in the root environment. It was a result of adequate application frequency of nutrient solutions during a day.

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