Estratégias de uso de águas salobras no cultivo da cebolinha em hidroponia de baixo custo

Abstract

The hydroponic cultivation with the use of brackish water constitutes an alternative for the agricultural production, especially of vegetables in the Brazilian semi-arid. Therefore, the present study was carried out to evaluate the water relations, the dry matter partition and the production of chives (Evergreen Nebuka All Year) in low-cost hydroponics using brackish water in the preparation and replenishment of the nutrient solution. For this, two tests were conducted in a protected environment (greenhouse), in the Agricultural Engineering Department of the Federal Rural University of Pernambuco - DEAGRI / UFRPE, in Recife-PE (8º 01 '05 "S and 35º 56' 48" ); the treatments consisted of six salinity levels of the nutrient solution (1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 dS m-1) and two circulation frequencies (twice daily - at 8 and 16 hours, and three times a day - at 8, 12 and 16 hours). In Test I, the replacement of the evapotranspiration was performed with the brackish water used in the preparation, and in Test II, with water supply (0.12 dS m-1). The experimental design in both trials was completely randomized, in a 6 x 2 factorial scheme, with five replications. The variables of water relations were analyzed: water consumption, water use efficiency in the production of phytomass (fresh and dry) of the aerial part, water content in the plant. It was also studied the root-shoot ratio and the dry matter partition of shoot and root. In another analysis, the production was evaluated: fresh and total dry matter, of the aerial part and of the root; the percentage of total dry mass, of the aerial part and of the root, and also the length of the root and the height of the plant. It was concluded that although the electrical conductivity of the nutrient solution affected water relations and chives production up to 9.0 dS m-1, the water content of chives was higher than 89% in all parts of the plant. The increase in circulation frequency mitigated the losses in consumption and water use efficiency, however, with increased salinity, dry matter allocation in the root increased, to the detriment of aerial part. Finally, it was verified that the use of three circulations of the solution per day attenuated the losses in the biometric variables and in the production of fresh and dry phytomass of the plants under replacement with brackish water.