Production, water consumption and nutrient content of Chinese cabbage grown hydroponically in brackish water

Abstract

Underground water reserves in the semi-arid region of Brazil are stored in the crystal formations that in large
part have high concentrations of salt. However, the scarcity of this resource makes the use of this water necessary for various
activities, including agriculture. The aim of this study was to evaluate the use of brackish water on the electrical conductivity and
pH of the nutrient solution, and on the production, water consumption and the uptake of nutrients in Chinese cabbage (Brassica
pekinensis L.) under a hydroponic system. The experimental design was completely randomised, with four replications and six
levels of water salinity (0.2, 1.2, 2.2, 3.2, 4.2 and 5.2 dS m-1), obtained by adding NaCl to the local water supply, with this water
being used to prepare the nutrient solution and to make up the volume lost through evapotranspiration. The results showed that
with the exception of the treatment at the lowest salinity, there was a tendency to increased electrical conductivity of the nutrient
solution with the increasing salinity of the water; that the pH of the nutrient solution remained within the normal range throughout
the cycle; that with the increasing salinity of the solution there was a reduction in all growth and production variables under
analysis, in water consumption, and in leaf N, K, Ca and Mg, and an increase in leaf concentrations of Na and Cl. It is possible to
use brackish water for the production of Chinese cabbage when grown hydroponically as an alternative for those producers who
have an available supply of brackish water and a restricted supply of fresh water, however with a reduction in productivity.