2019 ASHS Annual Conference

The mint is economically important for its fresh and dry leaves and its essential oil. Little is known about mint production with organic substrates and how growth and development indicators change. This is important, due to its great marketing potential in the food, pharmaceutical and cosmetic markets, and mainly for the characteristics that the market demands from it. Mint plants were grown under greenhouse conditions, four organic fertilizers were evaluated, namely Vermicompost, Compost, Biovital® and Worm Leachate, plus a chemical fertilizer, Steiner Nutrient Solution. Production and quality of biomass and essential oil was considered. Leaves were harvested 120 days after transplanting, when the first flowers were observed. The Steiner solution was the best fertilization in terms of showing the highest biomass yield. Regarding the organic fertilizers, Biovital® was the best treatment for biomass yield variables. The best treatments for essential oil content were the Steiner Nutrient Solution and Worm Leachate. The treatment with the lowest chlorophyll accumulation was the one using Biovital®. On the other hand, chlorophyll content and SPAD units, showed a high correlation (R²=0.94). Finally, the fertilization sources used in this experiment had no significant effect on the composition of the essential oil. The GC-MS analysis showed myrcene (Rt9.02), eucalyptol (Rt 10.09), limonene (Rt 10.11), linalool ( Rt12.18), menthone (Rt 14.08), piperitone oxide (Rt 16.65) and chavibetol (Rt19.23), which were identified as function of retention time (Rt) and according to the Spectra Library NIST V. 2008. These compounds were in very low concentrations in all the treatments, so they were not analyzed statistically. No menthol content was detected, probably due to its degradation during oil isolation, or the moment of taking the leaf samples.

Key words: Mentha piperita, vermicompost, compost, worm leachate, SPAD units.