The Effect of Wood Fiber Density on the Content of Macro And Microelements in the Root Environment of Greenhouse Cucumber

Wood fiber is a biodegradable growing substrate. In the years 2007-2008 the investigation on macro and microelement content changes in the nutrient solutions collected from the root environment of greenhouse cucumber cv. Onyks F₁ grown in the wood fiber slabs with differentiated density (60, 80, 100 g·dm^-3) was done. Results were compared with the rockwool at the density of 60 g·dm^-3. Increase of the wood fiber density to 80-100 g·dm^-3 significantly increased in the root environment the contents of ammonium, manganese, copper, boron and sodium. At high density of the wood fiber - 100 g·dm^-3, there was a distinct increase of the nutrient solution EC in the root environment. On the other hand, no differences were found in the pH value. In the root environment of plants grown in the rockwool, a higher content of ammonium, nitrates, iron and boron was found, while in the wood fiber, there was a greater amount of calcium and copper. In the root environment, there occurred the effect of nutrient increasing concentration, which for the rockwool was the following: Na>Zn>Cu>Ca>Cl>K>B>Fe>N-NO₃>Mg>S-SO₄>N-NH₄ (P and Mn did not concentrate). This sequence for the wood fiber, calculated for the average density 60-100 g·dm^-3, was: Cu>Na>Zn>Ca>Cl>K>B>S-SO₄>Mg. The decreasing effect of N-NH₄ and N-NO₃ contents in the wood fiber can be connected with the biological sorption because of a high C:N relation in this root medium (C:N=125).