Eficiência de doses de nitrogênio e sombreamento na cultura do tomate em cultivo protegido

Abstract

Several factors influence the productivity and end quality of the fruits of the tomato crop, among them, mineral nutrition, especially nitrogen nutrients and factors that interfere with the culture environment of the crop, such as shading of plants. Aiming to maintain the productivity and quality of the tomato fruits in the off season of the crop in RS, the objective of this work was to evaluate the influence of 50% black shading screen, nitrogen fertilization and the interaction between the two factors, on the agronomic performance of the tomato crop under protected environment. The present work was conducted in the greenhouse at the Biomonte Research and Development Company, in the agricultural crop 2016, geographical coordinates 29 ° 39,059 'South and 53 ° 57,413' West and altitude of 180.0 meters. The experiment was in DIC (completely randomized design) with factorial arrangement 2 x 5, and twenty repetitions. Two environments were used (with and without black shading screen 50%, sombrite® type) and five doses of N (0, 75, 150, 225 and 300 kg ha-1), according to the need of the crop and soil analysis used in the experiment, being the dose of 150 kg ha-1 of N, the recommended dose for the conditions of the present study. In order to evaluate the agronomic performance and crop productivity, were verified daily the climatic variables in the two environments and quantified the height and diameter of the plants, leaf area, chlorophyll content, stomatal behavior, yield (weight, diameter and length of fruits) and dry mass of shoots; for the evaluation of fruit quality, the pH, soluble solids, titratable acidity and SS / AT ratio of tomato fruit pulp were analyzed. The factors shading and N doses had influence on the agronomic performance, productivity and quality of tomato fruits, in cultivation in a protected environment. In the present experiment, the variables analyzed presented better responses in the non-shading condition of the plants than in the shaded plants. With regard to nitrogen, nutrient application contributed to a better growth and development of the plants, crop productivity and fruit quality up to a given dose (225 kg ha-1 in both environments). At the doses prior to and at the subsequent doses, tomato plants showed lower growth and development and lower productivity and fruit quality, indicating toxicity caused by excess N. From these data, it was concluded that, the conditions of the Experiment, for the option of cultivating the tomato under protected environment, in the crop off season, the dose of N used should be adjusted for higher fruit productivity and quality, and it is not necessary to use a 50% black shading screen.