Changes of Macro and Micronutrients Contents in the Root Environment of Greenhouse Tomato Grown in Fiber Wood Wood fiber can be used in horticultural practice as biodegradable horticultural substrate. In these studies carried out in the years 2007-2008, changes of the macro and micronutrients in nutrient solution collected from the root environment of greenhouse tomato cv. Emotion F1 grown in the slabs of wood fiber with densities of 60, 80 and 100 g·dm-3, were determined. Results were compared with the tomato growing in the rockwool slabs of density 60 g·dm-3. Increase of the wood fiber density from 60 to 100 g·dm-3 significantly declined the contents of N-NO3, P, K, Ca, S-SO4 and Fe in the root environment, but increased the N-NH4 and Mn contents. No significant effect of the wood fiber density on the changes of Mg, Zn, Cu, B and Na contents was found. Decrease of the main nutrients in the root environment of plants grown in the wood fiber with an increasing density, significantly decreased EC in nutrient solution. However, there were no significant changes in the pH value. In the growing of tomato on the rockwool and wood fiber slabs, in comparable density of 60 g·dm-3, there was a significant differentiation of the N-NH4, N-NO3, K, Fe and Zn contents in the root environment. Growing of plants in the wood fiber it was shown the higher contents of N-NO3, K and Zn, but in the rockwool the higher amounts of N-NH4 and Fe. The lowering series of nutrient contents in the rockwool showed the following sequence: Na>Fe>Ca>N-NH4>Cu>K>Cl>N-NO3>Mg>S-SO4>B, while in the wood fiber was: Na>Zn>Ca>N-NO3K>Mg>Cl>S-SO4>B. In the wood fiber, in contrast to the rockwool, there was no effect of Cu, Fe and N-NH4 concentration.