Organic substrata applied in greenhouse cultivations are biodegradable. Decomposition occurs during vegetation and as a waste during composting or ploughed in the field. The aim of the presented studies, conducted in the years 2008 and 2009 was to demonstrate the contents of macrocomponents in the solution from root environment of substrata and in tomato leaves. The tomato of Admiro F₁ cultivar was grown in the following substrata: 1) triticale straw, 2) triticale straw + high peat (3:1 v/v), 3) triticale straw + pine bark (3:1 v/v), 4) rockwool. Straw, cut into 2–3 cm pieces, straw with peat and bark were placed in plastic boxes (height twice as large as width). There was 15 dm³ of organic substrata and rockwool. During tomato vegetation in organic substrata there was the least of N-NO₃ at the beginning of growing (March), which could be related to biological sorption of nitrogen. In the subsequent months of cultivation the content of this nutrient was normal, according to the leaves recommended for tomato. Mean content of N-NH₄, N-NO₃, K, Ca, Mg in organic substrata did not significantly differ compared to rockwool. The EC value in organic and rockwool substrata was optimal during the whole vegetation period. The correct growth and high yield of tomato grown in organic substrata was obtained at the following mean contents in solution from root environment (mg dm^-3): N-NH₄ – 26.8, N-NO₃ – 242.8, P –78.1, K – 295.6, Ca – 315.3, Mg – 107.5.

35-45