Lignite as a new medium in soilless cultivation of tomato

Thus far, lignite has not been used as a growing medium in soilless cultivation. The aim of the research conducted in 2011-2013 was to develop a new growing medium made of lignite, and to determine the suitability of such a medium to prolonged soilless cultivation of tomato under greenhouse conditions. Lumps of lignite were crashed and sifted to obtain fractions of lignite particles 20, 10, 2.5 mm in diameter of and the earthy fraction. Cultivation mats measuring 100 x 20 x 7 cm were made of the particular fractions and a mixture of lignite fractions. These substrates were used in a prolonged cycle cultivation of the tomato cultivar Growdena, with the results compared to its cultivation in Grodan-Grotop rockwool. The crashing of lignite into small-grain fractions changed the substrate’s pH, salinity and concentration of S-SO4. Smaller lignite fractions resulted in the reduction of the medium’s pH and an increase of the salt content, particularly sulphate. Together with the crashing of lignite, the bulk density and water capacity increased, while the air capacity decreased. The most preferred air and water properties at pF=1.0 occurred in the medium with the fraction of lignite particles 2.5 mm in diameter and in the media formed by mixing different lignite fractions. The pH of the solution taken from the cultivation mats made of lignite was similar to the pH of the nutrient from rockwool. The concentration of nutrients in the lignite media throughout the whole cultivation period was similar to the concentration in rockwool. There was no biological sorption of nitrogen in the initial period of tomato cultivation on lignite and rockwool. The highest early, marketable and total yields of tomato fruits from cv Growdena F1 were obtained in the cultivation on mats made of the lignite fraction with particles 2.5 mm in diameter. These yields did not significantly differ from the marketable and total yields obtained in rockwool.