Light quality and organic fertilization promote growth and alters oxidative stress and essential oil composition of Thymus vulgaris L.

Abstract

The cultivation of thyme (Thymus vulgaris L.) requires management information that implies strategic gains in plant production and phytochemical properties. In this sense, the objective was to study the influence of cultivation under different conditions of light and organic fertilization on oxidative stress and phytotechnical, physiological, nutritional and quantitative-qualitative characteristics of thyme essential oil, in Lavras-MG, Brazil. For this, three experiments were conducted in which they were evaluated: dry weight of leaves, stem, root and total; photosynthetic pigments; macronutrient and micronutrient; non-enzymatic antioxidant activities; as well as parameters related to the production and quality of essential oil (OE). In the experiment of light conditions, thyme was grown in the fall and spring seasons in full sun and under blue, black and red nets. Thus, it was observed that the spring season brought significant gains for the plants regardless of the light conditions. In contrast, the full sun provided greater antioxidant activity, greater dry weight and OE yield in relation to the crops under nets. To assess the effects of organic fertilization, two experiments were conducted. In the first, thyme was grown without fertilization and with organic fertilization (Dose of 8 kg m-2 of proportional mixture of quail, cattle and goat manure) and chemical fertilizer. In this experiment, the application of organic fertilization resulted in expressive gains in the dry weight of the plants, accumulation of macronutrients and micronutrients and in the content and yield of thymol in the leaves. In the second fertilization experiment, the plants were subjected to treatments: control (without fertilization), chemical fertilization and fertilization with three sources of manure (quail, cattle and goat) in four doses (2, 4, 8 and 12 Kg m-2). Quail and cattle manure resulted in greater gains in dry weight and a large part of leaf nutrients, in relation to goat manure and chemical fertilization. In general, the plants showed linear and quadratic responses to manure doses. Plants grown with 12 Kg m-2 of cattle manure obtained the highest OE yield, reaching 710% higher than the control treatment. It is concluded that the best alternatives for the cultivation of T. vulgaris in the region of Lavras-MG, are the spring season and the condition of full sun Organic fertilization maximizes plant production and the yield of compounds of interest to thyme; The cattle and quail manure at doses between 8 and 12 Kg m-2 indicated to be a reference option in the fertilization of thyme.