Relações hídricas, características morfofisiológicas e produtivas da couve-flor em cultivo hidropônico NFT com águas salobras

Abstract

In hydroponic systems, crops, especially fast-growing crops, such as cauliflower, provide the sustainable use of brackish water. This fact creates a new perspective for the Brazilian semiarid agriculture, also collaborating with greater environmental security, increased employment and quality of life. The objective of this work was to evaluate the use of brackish water, used for the preparation of the nutrient solution and for the replacement of the evapotranspirated leaf, and flow rates of application of this solution on the water relations, morphological and productive characteristics of cauliflower cv. "Piracicaba Precoce". The researches were carried out in the Department of Agricultural Engineering of the Federal Rural University of Pernambuco, in a protected environment. Real situations of brackish water utilization were studied for the preparation of the nutrient solution, where: CEsolution was variable over time, tending to be decreasing for water with CEa equal to 0.2 dS m-1 and increasing for brackish waters . The experimental design was a completely randomized design in a 6 x 2 factorial design, with six saline levels (0.2, 1.5, 2.5, 3.5, 4.5 and 5.5 dS m-1) of (1.5 and 2.5 L min-1), with four replications, totaling 48 experimental plots. The data were submitted to analysis of variance by the F test (0.05) and when significant effect was verified, they were submitted to regression analysis (salinity levels) and analysis of means comparison (flow rates of nutrient solution) by the Tukey test at 5% probability. The increase in water salinity increased the water stress index and reduced leaf succulence. The salinity of the water reduced the leaf potential and the total water consumption of the crop, however, the effects were more pronounced in the flow of 2.5 L m-1. The flow rate of 2.5 L m-1 provided the highest water stress index and the lowest leaf succulence. The increase in water salinity reduced the water use efficiency of fresh and dry biomass of the aerial part, water content of the root and aerial part and the biomass production index of the aerial part and increased the aerial root ratio, however , the effects were more pronounced in the 2.5 L min-1 flow.