Abstract
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 Verão’ 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.
Highlights
Lettuce (Lactuca sativa L.) is a leafy vegetable that presents broad adaptation to several environments, low production cost, low susceptibility to plague and diseases, easy handling, short cycle, high productivity and economic profitability, being one of the most cultivated specie through Brazilian regions (Araújo Neto et al, 2012). This oleraceous originates from temperate climate countries, which makes its cultivation in tropical climates a challenge for producers, due to the low productivity and bad quality of leaves caused by increased luminosity and temperature (Blind & Filho, 2015; Guerra et al, 2017)
We evaluated the effect of dry matter accumulation (Pinheiro et al, 2016; Guerra et al, 2017)
When isolated, the shading levels influenced the plant height, stem diameter, and root length, while cultivars differ in plant height, number of leaves and leaf area (Table 5)
Summary
Lettuce (Lactuca sativa L.) is a leafy vegetable that presents broad adaptation to several environments, low production cost, low susceptibility to plague and diseases, easy handling, short cycle, high productivity and economic profitability, being one of the most cultivated specie through Brazilian regions (Araújo Neto et al, 2012). In semiarid regions, where environments present high luminosity and temperature, the culture cannot grow and develop according to its maximum genetic potential Under such conditions, plants tend to shorten the cycle, reducing in addition the quality, while yielding fibrous, small and bitter leaves (Luz et al, 2009). Plants tend to shorten the cycle, reducing in addition the quality, while yielding fibrous, small and bitter leaves (Luz et al, 2009) These factors can be minimized by using shading screens, which work to reduce the deleterious effects of high radiation and temperatures (Silva et al, 2015; Pinheiro et al, 2016), providing a microclimate appropriate to the development of the crop (Kotilainen et al, 2018). 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
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