Shading on Yield and Quality of Lettuce Cultivars in Semiarid Conditions

Lettuce is a crop originating from temperate climate, and for this reason, when cultivated in semiarid region, characterized by high luminosity and temperature, major losses in productivity and quality occur. The objective of this work was to evaluate the influence of different levels of shade on yield and quality of lettuce cultivars in semiarid conditions. The experiment was conducted under field conditions at the Human and Agricultural Sciences Center at State University of Paraiba, Brazil, in randomized blocks with parcels divided into 4 × 4 factorial space, and four repetitions. The parcels received different shading levels (0, 30, 50 and 70%) with black polypropylene screen and sub parcels by lettuce cultivars: ‘Americana Irene’, ‘White Boston’, ‘Regina de Verao’ and ‘Green Salad Bowl’. The shading promoted higher performance in height, stem diameter, root length, pH and dry mass of lettuce plants when compared to those grown in the open-air, being the shading of 70% the more efficient. The ‘Americana Irene’ cultivar was distinguished in terms of plant height, foliage area, leaves dry mass and soluble solids, independently from the cultivation environment. With the shading, this cultivar improved the aerial shoot-root ratio and root dry mass.