Biomass production and essential oil of lemon balm cultivated under colored screens and nitrogen

The aim of this study was to evaluate the effect of light quality and nitrogen availability on the biomass production, yield and composition of essential oil of lemon balm (Lippia alba). Five doses of N (0; 40; 80; 120 and 160 kg ha-1) were studied, using urea and three light quality conditions obtained with the use of colored shading nets (blue and red), 50% irradiance and under full sun. The experiment was arranged in a 5x3 factorial scheme, in split plots, with seven replicates. After 60 days of cultivation under the shading nets, a higher dry leaf biomass (4.83 g per plant) was observed in the plants under blue net cultivation at a dose of 102 kg ha-1 of N. The plants grown under full sun presented greater amount of neral and geranial, major components of the essential oil of the lemon balm, which give commercial value to the species. The use of colored shading nets does not influence the composition of the essential oil of lemon balm, but increases the concentration of the compounds found in it. Nitrogen does not affect the quality of the essential oil of lemon balm, but it provides higher oil yield (0.27 g per plant) at the dose of 65 kg ha-1 of N.