Malhas coloridas e adubaçao verde na produção de biomassa, óleo essencial e compostos químicos, no cultivo de Ocimum basilicum L. (Lamiaceae)

Abstract

Ocimum basilicum L. (Lamiaceae), commonly known as basil, is a plant native to India with medicinal and culinary properties. It is used in folk medicine for its antispasmodic, antiseptic, galactogenic, and anti-helminthic properties, among others. The plant is also known by common names such as "alfavaca" and "sweet basil." This study analyzed the production of biomass, essential oil, and photosynthetic pigments in basil through two experiments. The first experiment investigated the influence of different colored nets (red, black, and blue) and full sun exposure on the plant's cultivation. The second experiment analyzed the influence of green manure (Crotalaria juncea L.) in the production of biomass, essential oil, and photosynthetic pigments in basil. The seedlings were obtained from 7 cm long apical micro-cuttings, which were grown for 30 days in 10-liter pots. For the netting experiment, a completely randomized design (CRD) was used, with 4 treatments (full sun, red, black, and blue), 5 repetitions, and 5 plants per repetition, for a total of 25 plants per treatment and 100 plants overall. The plants were collected at 75 days. In the green manure experiment, a completely randomized design (CRD) was also used, with 6 treatments (0, 150g, 300g, 450g, 600g, and chemical), 4 repetitions, and 4 plants per repetition, for a total of 16 plants per treatment and 96 plants overall. The plants were harvested after 78 days of cultivation. The following parameters were evaluated: dry biomass of leaves, stems, roots, aerial parts, and total; essential oil content and yield; photosynthetic pigments; total phenols; flavonoids; and ORAC. The Scott-Knott test (p < 0.05) was used for variance analyses with the aid of the statistical software SISVAR for mean comparison. In the netting experiment, cultivation under full sun resulted in gains in dry mass production for leaves, aerial parts, and total biomass of 68.9%, 58.3%, and 63.1%, respectively, when compared to the blue net. The blue and black nets resulted in higher average essential oil content. However, the highest essential oil yield occurred under full sun (0.20 g EO/plant). The highest concentration of 1,8-cineole occurred under the red net (22.92%), while camphor had the highest content in full-sun cultivation (17.25%). The control group (no green manure) showed the lowest average dry biomass compared to the highest dose of 600g/pot. For dry leaf biomass, the highest dose of green manure showed similar results to the chemical fertilizer treatment. The accumulation of nitrogen, calcium, and sulfur in the basil leaves from the highest dose of green manure (600 g/pot) was similar to that of chemical fertilization. Doses of 150, 450, and 600 g/pot resulted in significantly higher chlorophyll a, concentrations compared to the control. The highest averages for both essential oil content and yield were obtained with the highest dose of green manure. Regarding linalool, the highest concentrations were found in the 150 and 300 g/pot doses, at 38.60% and 38.19%, respectively. The results provide important information that can help basil farmers. Cultivation under full sun yielded better results than under colored nets, and the use of green manure proved to be viable at higher dosages.