Effect of nutrient solution, effective microorganisms (EM-A), and assimilation illumination of plants on the induction of the growth of lettuce (Lactuca sativa L.) in hydroponic cultivation

Abstract

The main aim of the present study was to evaluate the influence of the chemical composition of a nutrient solution (NS I, NS II), seed inoculation with Effective Microorganisms (EM), and assimilation illumination (AI) of plants on the growth, development and nutritional status of lettuce ( Lactuca sativa L.) in hydroponic cultivation and microbiological changes in the medium. The measurements were as follows: quantity of leaves per plant (LQ), surface area of the biggest leaves of plants (SBL), relative chlorophyll content (SPAD units), total fresh weight (TFW), total dry weight (TDW), percentage (%) of dry matter (% DM), chemical composition of leaves, nutrient uptake (N, P, K, Ca, Mg, Na) of the aboveground parts of the plant. It was shown that the simultaneous inoculation of seeds with EM and application of NS II had an effect on improving seed germination (1st–5th day after sowing), but a significantly positive influence of NS I on seed germination was found from the 5th to 9th day. The application of NS II and EM-A had a positive influence on the development of leaves on the plant. The chemical composition of the nutrient solution was found to have a significant effect on the biometrical parameters of plants. The use of supplemental lighting in cultivation of lettuce affected positively both the growth and development of plants. The chemical composition of the nutrient solution significantly modified the macronutrient nutrition status of plants, while the illumination of plants only in case of phosphorus – but at the same time it had a significant influence on the uptake of all nutrients by the plant. The influence of EM was not proved. The microbiological analysis showed a significant influence of the chemical composition of nutrient solutions on the changes in the numbers of the analyzed groups of microorganisms, showing an increase in their numbers in nutrient solutions with higher contents of chemical elements. However, there were no significant changes in the number of microorganisms relative to the treatment with assimilation illumination and to that of seed inoculation with EM solutions.