Produção de fitomassa de manjerona e menta em intervalos de colheita e de óleo essencial em estações do ano

Abstract

Spice, medicinal and aromatic plants such as marjoram (Origanum majorana L.) and peppermint (Mentha x piperita L.) are of interest to the food and pharmaceutical industries. The aims of this work were to define the appropriate harvest interval for phytomass production and the season for essential oil production of marjoram and peppermint in summer and winter transplants. Two experiments were carried out for each crop, in an off-ground cultivation system, in a protected environment, the first with summer transplantation and the second with winter transplantation. Fresh and dry matter masses of leaves, branches and shoots were evaluated in a completely randomized design with five treatments, being the intervals between successive harvests of 30, 45, 60, 72 and 90 days from transplantation, with four repetitions. At 12 months after transplantation, the masses of each harvest, in each repetition, were summed to obtain the accumulated production. The daily increment rate was determined by relating the cumulative yield data of the crops (y) versus the days after transplantation (x) over the 12 months, obtaining a linear equation y = bx + a for each repetition, in each interval, where b is the slope of the line, equivalent to the daily increment rate. For the evaluation of the essential oil, a completely randomized design was used, with four treatments, being the seasons of the year. Plants were collected every 30 days, in a period of 12 months, and leaf samples of three consecutive harvest cultivated at the same season were joined. The content, yield and chemical composition of the essential oil were determined. The fresh matter mass of marjoram leaves was higher at 60 and 90 days in the summer transplant and at 72 and 90 days in the winter transplant. The fresh matter mass of peppermint leaves was similar between harvest intervals in the summer transplant and higher at 60 and 90 days in the winter transplant. In the summer transplant, the content and yield of marjoram essential oil were higher in the summer and spring seasons. In the winter transplant, the oil content was higher in summer and the yield in spring season. The peppermint essential oil content was higher in the summer and the yield was higher in the spring. Marjoram harvests at 60-day intervals in summer transplants and 72 days in winter transplants are most appropriate for phytomass production. Peppermint harvests at 60-day intervals, in winter transplant, are more appropriate for phytomass production and in summer transplant at 45-day intervals. The best production of marjoram and peppermint essential oil is obtained in summer and spring harvests, with mint transplantation performed in summer, because in winter there is mentofuran production in the essential oil, which reduces its quality.