Influência do silício na nutrição nitrogenada da berinjela.

Abstract

The eggplant (Solanum melongena L.) is a vegetable fruit that belongs to the solanaceous family,considered demanding in nitrogen for adequate production. So, the supply of silicon (Si) may increase the efficiency of nitrogen fertilization and reduces the doses to be applied. The study aimed to evaluate the fertilization effect with N and Si, and Si x N interaction on growth, physiological aspect, silicon and nitrogen nutrition, aiming at increasing the nitrogen efficiency fertilizer, and also increasing of productivity and eggplant fruit quality. Two experiments in completely randomized design were conducted at the Centro de Ciências e Tecnologia Agroalimentar (CCTA/UFCG), Campus Pombal - PB, with eggplants cultivate "Embu". In the first experiment, treatments consisting of a 5 x 4 factorial arrangement, comprising 5 N rates (25, 125, 250, 350 and 500 mg dm-3) and 4 Si rates (0, 75, 150 and 200 mg dm-3) applied via root with four replications. In the second experiment, treatments consisting of a 5 x 2 factorial arrangement, with 5 N rates (25, 125, 250, 350 and 500 mg dm-3) and 2 Si rates (silicon and without foliar application of a 10 mmol L-1 Si) and six replications. During pre-flowering, were evaluated growth (dry matter production of leaves, stems and roots, and leaf area index); gas exchanges, which are photosynthetic rate, stomatal conductance, transpiration rate and intercellular CO2 concentration; the contents and accumulation of fractional nitrogen (NO3-, NH4+, and total and organic), the estimated N use efficiency (NUE) and Si content in the leaves. In the second experiment, in addition to the aforementioned variables were also evaluated the number of fruits per plant, yield per plant, average fruit weight, the longitudinal and transverse diameter, firmness, °Brix, the pH of the pulp, the vitamin content C and titratable acidity. Nitrogen fertilization increased the yield in dry matter production, gas exchange, the levels of N fractions as well as their accumulation, increased the quality attributes of the fruit, but decreased the Si content in leaves and N utilization efficiency (EUN). Silicon fertilization applied via roots elevated the content and accumulation of N-NH4+ in the leaves , the accumulation of N-NH4+ in the roots , and the Si content in the leaves , the concentration and accumulation of N-NO3- in roots and decreased and N-NO3- accumulation in leaves without influence on growth and gas exchange. Silicon fertilization foliar applied negatively influenced the rates of transpiration and photosynthesis; decreased levels of N-NH4+ in leaves , N-NO3-, N-organic and N-total in the stem, and increased the content of N-NO3- in roots; positively influenced the NUE; yielded increases in fruit size, in °Brix, and decreased acidity of the fruits. It was concluded that eggplant responded positively to nitrogen fertilization, providing increases in growth, gas exchange, the levels of N fractions, but with a negative effect on NUE and leaf content in Si. Silicon exerted influence on foliar concentrations of fractions N and nitrate in roots, and fruit quality.