Desempenho do cultivo de agrião hidropônico com águas salobras e diferentes tempos de circulação da solução nutritiva

Abstract

The use of lower qualitywater in agriculture has become a suitable alternative, in view of the restriction of good quality water. Thus, the objective of this work was to evaluate the use of brackish water in different times of circulation of the nutrient solution in the production of the wide leaf watercress culture in hydroponic NFT (laminar nutrient flow technique).The experiment was conducted in a protected environment from december 2018 to march 2019 (two crop cycles). The treatments were distributed in a randomized block design in a 5 x 2 factorial scheme, five water salinity levels (ECw: 0,6; 1,6; 2,6; 3,6 and 4,6 dS m-1), and (10 and 15 min), totaling 10 treatments in a 5 x 2 interaction with 4 replicates, resulting in 40 experimental plots. The evaluated parameters were plant height, leaf number, stem diameter, root length at 6; 10; 14; 20 and 25 days after transplanting (DAT), leaf area, fresh matter mass of the area and root, shoot dry matter mass, photosynthesis, transpiration, stomatal conductance,moisture contente,SPAD index and proline in both cycles. The data obtained were submitted to the normality test and, afterwards, the analysis of variance (Test F), when significant effects were verified, were submitted to regression analysis for quantitative data and Tukey test when qualitative at 5% probability (P < 0.05). The increase in water salinity levels, in both crop cycles evaluated, influenced most of the analyzed variables. There was a decrease (0,83 and 0,57 g plant-1) for root dry mass (cycle 1) and (7,41 and 6,62 g plant-1) for fresh root mass (cycle 2); (5,0354 and 5,6996 g plant-1in the first cycle and 5,6309 g plant-1in the second cycle) for the shoot fresh matter mass (0,6643 and 0,7577 g plant-1in the cycle 1 and 0,6395 and 0,6615 g plant-1in cycle 2) inthe aerial shoot dry mass. Without cycle 1 the maximum photosynthetic without time 10 min and time 15 min. From 20,88 and 20,02 mmol m-2s-1, for stomatal conductance was 0,44 mol m-2 s-1causing decrease 63,37% and transpiration was 5,02 mmol m-2s-1with losses of 37,85% when submitted to the maximum ECw current and the proline content increased 61,92% without higher saline level in relation to the lower ECw. No cycle 2 maximal transpiration without time 10 min was 8,73 mmol m-2s-1, without time 15 min,with ECw indicators of 2,6 and 4,6 dS m-1, a proline was 178,42 μmol g-1MS, 34,43% reduction in relation to the lowest ECw value. Among the times of circulation of the nutrient solution the 15 min was the one that provided the best results for the variables analyzed in both cycles, except for the dry mass of the root in cycle 1.