Growth of moringa under different concentrations of nutrient solutions prepared with brackish water

Abstract

The water scarcity in semi-arid regions, such as the Brazilian Northeast, has led to the use of brackish waters for crop irrigation, motivating to alleviate the freshwater scarcity. However, using this type of water presents challenges both in terms of soil salinization and plant response to salt stress. Therefore, cultivating species that are tolerant to salinity can be a strategy for utilizing such waters. In this context, one species with potential for cultivation under such adverse conditions is moringa (Moringa oleifera Lam.). This study aimed to evaluate the initial growth of moringa in a floating hydroponic system under different concentrations of nutrient solution prepared with brackish water. The experiment was conducted in a greenhouse using a randomized block design in a 2 × 4 factorial scheme: two levels of electrical conductivity of water (ECw) (0.3 and 5.0 dS m^-1 with NaCl) were combined with four nutrient solution concentrations (NSC) (25, 50, 75, and 100%). Each experimental unit consisting of one 2-L plastic pot. The plants were grown under these conditions for 25 days, with non-destructive evaluations performed every five days (from 10 to 20 days) for the following parameters: plant height (PH), stem diameter (SD), number of leaves (NL), and chlorophyll a and b indices (Chla and Chlb). At the end of the experiment (at 25 days), in addition to the biometric evaluations, the shoot fresh matter (SFM) and shoot dry matter (SDM) were determined, along with Na⁺, K⁺, and Cl^- contents and Na⁺/K⁺ ratio in the leaf and stem tissues of the plants. The biometric variables (PH, SD, and NL) were independently affected by salt stress, with variations depending on the evaluation period. Chla and Chlb showed differential responses to salt stress, varying according to NSC and evaluation periods. Leaf and stem K⁺ content showed significant changes in response to individual factors, whereas Na⁺ and Cl^- content and the Na⁺/K⁺ ratio exhibited interactive effects between factors. Under salt stress conditions, SFM and SDM production reached maximum values at NSC of 62.75 and 64.38%, respectively. Therefore, these findings demonstrate that under saline conditions, nutrient solution concentrations can be effectively reduced while maintaining plant biomass production.