Utilização de plantas para redução de salinidade da água e produção de biomassa por meio de cultivo hidropônico

Abstract

The shortage of surface water and the restricted use of saline groundwater is a common reality of the Brazilian semiarid region, including areas of the State of Minas Gerais. This study aimed to contribute to the development of knowledge about safe use of saline water resources through hydroponic growing, plant species adapted and nutrient solutions (A1, A2 and A3) to which three different concentrations of sodium chloride have been added (300, 500 and 1,000 mg L-1 Na+), simulating some physicochemical properties of the local groundwater. Physicochemical and quantitative changes in the saline nutrient solutions, as well as biomass accumulation and visual symptoms of stress in the plants were analyzed. The first experiment compared three plant species (vetiver grass (CV), water hyacinth (WH) and purslane (PU)), highlighting the comparison between AG and BE: (1) the evaluation of relative growth rate indicated that PU performed better than water hyacinth, with lower consumption of nutrient solutions (similar to control treatment) and equal or higher biomass accumulation, and (2) despite the significant volume reduction in all solutions, water hyacinth was significantly distinct in its estimated extraction of calcium and magnesium but did not show significant removal of sodium besides no chloride extraction, on the other hand, PU reached its better performance in the extraction of magnesium (50.5%) and sodium (15.9%), using solution A2. Considering, among other aspects, its high nutritional value, purslane was used in experiment II in two growing conditions (not clipped (NC) and clipped (CL)), being noticed: (1) NC treatments showed similar biomass accumulation regardless the solution applied, as well as CL treatments; (2) despite their higher consumption of nutrient solutions, NC treatments distinguished in relative growth rate as compared to CL treatments; (3) Extraction of calcium: using solutions A1 and A2, NC treatments reached (on average) 36.0 and 29.5%, while CL achieved 20.0 and 33.8%, respectively; (4) Extraction of magnesium: NC treatments were significantly distinct in their performance, averaging 95.9, 97.1 and 84.9%, as CL reached 85.4, 67.5 and 36.4%, respectively; (5) Extraction of sodium: NC treatments achieved (on average) 18.2, 15.0 and 9.8% while CL reached 15.5, 14.0 and 22.5%, respectively; (6) Extraction of chloride: only NC treatments, using solutions A1 and A2, showed (on average) 16.7 and 8.2%, respectively. Therefore, purslane was successful as a tolerant species but failed to accomplish its role as an accumulator of sodium and chloride as mentioned by the literature.