SIMULATION MODELS OF LETTUCE GROWTH IN RESPONSE TO ORGANIC AND MINERAL FERTILIZATION

Abstract

The effect of the simple or combined application of vermicompost tea (organic fertilization) and Steiner´s solution (mineral fertilization) at five concentrations (0, 25, 50, 75 and 100 %), on biomass production, leaf area, leaf number and plant height of lettuce (Lactuca sativa var. longifolia) cv. ‘Parris Island’ was evaluated under hydroponics. Results showed that the simple application of vermicompost tea at low concentration improved all variables measured. However, this effect turned negative as the concentration of vermicompost tea increased in the nutrient solution. Also, it was observed that low concentrations of vermicompost tea in combination with low levels of Steiner´s solution improved plant growth. Nevertheless, as concentration of both factors increased in the hydroponic culture, negative effects on all variables measured were detected, and such effects were more evident when vermicompost tea concentrations were high. The negative effects may be associated to high electric conductivity observed in treatments with the highest levels of both the vermicompost tea and the nutrient solution used.