Efluente doméstico tratado como fonte complementar de nutrientes no cultivo de girassol ornamental em sistema hidropônico

Abstract

The use of treated domestic effluents in agriculture has been important not only for being as an extra source of water, but also as a source of nutrients to crops. The objective of this work was to study the use of treated domestic effluents as a complementary source of nutrients for the production of ornamental sunflower (Helianthus annuus L. cv. Anão Jardim) in the DFT hydroponic system in two types of structures. Two experiments (Ibench, II, pyramid) were conducted simultaneously in a greenhouse in the completely randomized design with four treatments T1 - nutrient solution of Furlani 100% prepared in supply water (control), T2, T3 and T4 - nutrient solution of Furlani with 100, 75 e 50% concentration of the nutrients prepared in treated effluent, respectively, and six replications, totalizing 24 experimental plots, each plot consisting of 15 plants in Experiment I and 7 plants in Experiment II. At 45 days after transplanting (DAT) in Experiment I there was a significant effect on fresh (MFF) and dry mass of leaf (MSF) for the treatment with 50% nutrient solution prepared in treated domestic effluent (T4), presenting the lowest mean among them. In Experiment II the control treatment presented the highest mean differing significantly from the others. For fresh mass (MFC) and dry matter of the stem (MSC), the treatments T1 and T2 did not differ between themselves presenting higher means in comparison to other treatments. Significant effect of treatments was observed for the appearance of the floral buds (ABF) of sunflower cv. Anão de Jardim caused by different concentrations of nutrient solution in the two experiments. The control treatment (T1) and with 50% of the nutrient solution in treated domestic effluent (T4), did not differ between them, presenting a smaller interval of days for the ABF. Similar behavior was observed for the fresh (MFCAP) and dry matter of chapter (MSCAP) in both experiments, and the control treatment (T1) was significantly superior than the other treatments. The nutrient solution with 50% concentration of nutrients prepared in treated domestic effluent (T4) provided greater precocity and greater external diameter of the chapters when compared to the plants of the treatments in which 75 and 100% of the nutrient solution in treated effluent (T3 and T2) was used in the experiments. Calcium and magnesium content in the leaves and Ca content in stem for the T4 treatment in Experiment I presented reductions in comparison to the control treatment. As for water consumption, plants grown in both structures (bench and pyramid) expressed similar results, and plants cultivated in nutrient solution with 50% of nutrient concentration at 40 DAT presented the lowest water consumption, both in the bench and in the pyramid structure. At 15 DAT, the plants grown in nutrient solution with 50% concentration of nutrients in treated domestic effluent (T4) presented the highest water use efficiency differing significantly in relation to the other treatments, while at 30 and 45 DAT the treatment of 100% concentration of the nutrient solution prepared in treated domestic effluent (T2) was significantly superior to the others with the highest mean values for the water use efficiency. The nutrient solutions of different concentrations prepared in treated domestic effluent provided the growth and production of ornamental sunflower compatible with commercial standards. In both structures (bench and pyramid) treatment with 50% nutrient concentration in the solution prepared in treated domestic effluent (T4) provided results of the analyzed variables lower in comparison to the other treatments. In both experiments the treatments T2 and T3 for the studied variables presented results with about 78% of agreement, with maximum of 20% variation, when compared to the control treatment. The structure used in Experiment I (bench) provided superior results when compared o Experiment II (pyramid).