Adubação nitrogenada e potássica no desenvolvimento de Carthamus Tinctorius L.

Abstract

The safflower (Carthamus tinctorius L.) is a plant of the Asteraceae family with high productive potential of oil, being used for both human and industrial food and with great potential for the production of biodiesel. According to the literature, the species presents satisfactory productive indexes under adverse conditions, such as low water availability and poor soils, constituting an alternative for semi-arid and Brazilian arid regions. However, the lack of knowledge of basic cultivation techniques, such as nutritional demand of the crop, is still an obstacle to its introduction into the country. Thus, the objective of this work was to evaluate the effect of fertilization with different nitrogen and potassium rates on the growth and development of safflower plants grown under greenhouse conditions. The experiment was conducted using the experimental design in randomized blocks, arranged in a factorial scheme 5x5, corresponding to five doses of nitrogen (0, 50, 100, 150 and 200 mg dm-³) and five doses of potassium (0, 50, 100, 150 and 200 mg dm-³), with four replicates. Planting was carried out in May 2016 and the first evaluation of the experiment was carried out 60 days after planting, in which the following characteristics were evaluated: leaf number, height (cm), diameter of the stem (mm) and relative index of chlorophyll. Thirty days after the first evaluation, it was also determined: number of chapters and chapter diameter (mm), being evaluated again at 110 days after sowing. At harvest, 130 days after planting, the following were evaluated: dry mass of the aerial part (g plant-1) and, subsequently, the accumulation (mg plant-1) and nitrogen and potassium content in the aerial part (mg dm-3). The data were submitted to analysis of variance (ANOVA), regression test and response surface at 5% probability, using software R. The potassium fertilization presented a significant difference for all variables evaluated. The linear regression model was adjusted for all the characteristics evaluated, except for the second evaluation of the number of leaves and for the potassium content in the plant, which were adapted to the quadratic regression model. Only for the number of leaves, height of plants and accumulation of nitrogen, there was an isolated effect of nitrogen fertilization. There was a decrease in the number of leaves and height of the plants as the nitrogen doses was elevated. The potassium fertilization positively influenced the development of safflower, however, the range of doses studied was not sufficient to obtain maximum culture response. The safflower access plants studied are little influenced by the nitrogen doses.