Avaliação de genótipos de alface, no sistema NFT hidropônico: uma indicação de manejos nutricionais

Abstract

The management of the nutrient solution is the most important factor of hydroponics.Accompanying the CE value is fundamental, because if the water conductivity is too high, it is necessary to reduce the amount of fertilizer or vice versa. The objective of this work was to evaluate the growth of different genotypes of lettuce (Lactuca sativa L.) with the use of three electrical conductivities in the NFT system. The experiment was conducted in a commercial hydroponic greenhouse, located in the residential neighborhood Eldorado, metropolitan region of São Luís, MA (2°30'05.6 "south latitude, 44°13'50.4" west longitude and 24 m altitude). The experimental design was completely randomized, in a 3x8 factorial scheme with 3 replicates. The treatments were composed of different electrical conductivities of the nutrient solution (1,0mS cm-1,1,5mS cm-1 and 2,0mS cm-1) for the 8 lettuce genotypes: Brunela (G1), Gabriela (G2) , Crunchy (G3), Mediterranean (G4), BS AC0063 (G5), Rubinella (G6), Flange (G7) and Gloriosa (G8). The control treatment is represented by the conductivity 1,5mS cm-1. Three plants were collected from each replicate, for each treatment to perform the following leaf area evaluations, number of leaves per plant. Fresh part of aerial part and root and physiological parameter (SPAD). The data were submitted to analysis of variance (ANOVA). The means of the treatments were compared by the Tukey's test (p <5%). The statistical program used to perform the analysis of variance was the software AgroEstat 1.0. For the fresh root and shoot mass, there was no significant effect for the interaction between factors. There are significant differences that explain that the C.E. variation promoted a significant change for 5 of the treatments, in relation to the number of leaves (NF) parameter. In the analysis of variance for the parameter of leaf area, there is a significant effect for the factors analyzed individually and in the interaction between factors. There is significant interaction between genotype for chlorophyll production, however the factors were not significant their interactions. With results obtained in this work, it is considered that the electrical conductivity of 2.0mS cm-1, for environmental conditions of the city of São Luís, were obtained superior results in several parameters analyzed in this research, so the lettuce behaves better when submitted to conductivity. The results of this study may indicate an alternative for the production of hydroponic vegetables. The Gloriosa cultivar of the American group had very promising results for both the number of leaves as well as the chlorophyll content and the leaf area and the parameters parameters can explain the excellent performance of this cultivar in the environmental conditions of São Luís, when it reached greater weight of fresh matter of the aerial part