Salinity and flow rates of nutrient solution on cauliflower biometrics in NFT hydroponic system

Hammady R E Soares,José A Santos Júnior,Mário M Rolim,Gerônimo F Da Silva,Ênio F De F E Silva,Adiel F Da S Cruz

doi:10.1590/1807-1929/agriambi.v24n4p258-265

Abstract

ABSTRACT The use of brackish water in hydroponic crops represents an alternative for vegetable production. In this context, two experiments were conducted to evaluate the effect of using brackish water to prepare the nutrient solution and replace the evapotranspired depth, applied at different flow rates, on cauliflower biometrics in NFT (nutrient film technique) hydroponic system. In both experiments, the experimental design was completely randomized with four repetitions, in a 6 x 2 factorial scheme: six levels of water electrical conductivity (ECw) in interaction with two flow rates of nutrient solution application in the hydroponic channels (1.5 and 2.5 L min-1). In Experiment I, brackish waters with different EC (1.5, 2.5, 3.5, 4.5 and 5.5 dS m-1), obtained by the addition of NaCl in public-supply water (0.2 dS m-1), were used. In Experiment II, the chemical characteristics of brackish waters collected in the semiarid region of Pernambuco were simulated, with EC of 1.67, 3.30, 4.71, 5.88 and 13.84 dS m-1, plus the control (0.2 dS m-1). Increasing salinity reduced cauliflower growth. Flow rate of 1.5 L min-1 promoted the best results of shoot fresh and dry masses, leaf area, number of leaves, plant height and shoot diameter. The best water for cauliflower production was public-supply water and, among the well waters, the best was the calcium sulfate-rich water with EC of 1.67 dS m-1.

Highlights

The feasibility of using brackish waters to grow different leafy vegetables, especially in the context of hydroponic cultivation, is related to the absence of action of the matric potential, which has been widely proven by several studies (Soares et al, 2015; Cruz et al, 2018; Lira et al, 2018).In the context of the Brazilian semiarid region, brackish waters from wells have distinct natures and concentrations, which in turn influence plant development differently
In the nutrient solution prepared with public-supply water (0.2 dS m-1), there was a reduction in ECsol as a function of time at both flow rates (Figures 1A and B; 2A and B), in response to the replacement of the evapotranspired depth with low-salinity water (0.2 dS m-1) because, as the plants absorbed the nutrients necessary for their development, there was a reduction in electrical conductivity
Results similar to those found in this study were reported by Soares et al (2010), who worked with 7.46 dS m-1 salinity in the replacement of ETc with brackish water and found an increase in ECsol from 2.24 to 7.07 dS m-1 in 25 days of cultivation

Summary

Introduction

In the context of the Brazilian semiarid region, brackish waters from wells have distinct natures and concentrations, which in turn influence plant development differently. One of the problems encountered by producers in the NFT (nutrient film technique) system is the increase in nutrient solution temperature, which reduces the amount of dissolved oxygen for plants (Bremenkamp et al, 2012). In these cases, the increase in flow rate can provide lower temperatures during the hottest hours of the day, leading to lower effect of heat exchange on plants (Genuncio et al, 2011). The literature evidencing the joint effect of salinity and flow rates of nutrient solution application on cauliflower in NFT hydroponic system is still scarce

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Results

Conclusion