Produção e qualidade de híbridos de alface em função de níveis de sombreamento.

Abstract

The crop of lettuce in regions with high temperature and luminosity can affect its growth and development resulting in losses of yield and quality of its leaves. The objective of this work was to evaluate the growth, mass partition, yield and quality of lettuce hybrids grown under different levels of shading under the conditions of the Paraiba semi - arid region. The experiment was conducted in an experimental area of Campus IV of the State University of Paraíba, in the municipality of Catolé do Rocha - PB, from July to September, 2017. The experimental design was a randomized complete block in split plots 4 x 4, with 4 replicates. The plot consisted of different levels of shading (0, 30, 50 and 70%) from black shading canvas and in the subplots by four hybrids of different lettuce groups (American Irene, Boston White, Regina de Verão and Mimosa), grown at spacing of 25 x 25 cm. At the time of data collection were evaluated characteristics related to climate, growth, mass partition, production and quality of lettuce. It was obtained that the values of the temperature soil, air and radiation under lettuce plants were reduced in greater proportion with the elevation of the shading levels up to 70% and the relative humidity of the air was higher in the shading screen of 50 %. The shading levels adopted of 50 and 70% stood out in promoting the greater growth of the plant and partitioning of directed mass to shoot in comparison to the open crop. Lettuce crop with the American Irene hybrid showed fewer leaves, but bigger leaves regardless of the level of shading adopted. The highest fresh mass of the plant and yield was obtained in the American Irene hybrid when grown with shade screens of 50 and 70% compared to the open crop. The elevation of shading levels increased pH values and reduced total acidity and soluble solids in lettuce plants. The soluble solids values were higher in the Boston White hybrid only when compared to American Irene regardless of the level of shading.