Uso de águas subterrâneas salobras do semiárido pernambucano para produção de coentro em sistema hidropônico NFT

Abstract

The use of hydroponics allowed the rational use of existing brackish water sources in the semi-arid region, thus allowing agricultural production to contribute to minimizing soil degradation. In this sense, the present work aimed to evaluate the influence of salinity and flow rates of application of the nutrient solution on the development of coriander (Coriandrum sativum L.) in an NFT (laminar flow technique of nutrients) hydroponic system, using different brackish waters. The research was conducted at the Agricultural Engineering Department of the Federal Rural University of Pernambuco (8 ° 01 '05' 'south latitude and 34 ° 56' 48 '' west longitude, with an average altitude of 6.5 m), months November 2019 to March 2020, in a completely randomized design, in a 4 x 4 factorial scheme, with four replications, totaling 64 experimental plots. The treatments consisted of four different levels of salinity, namely: 1.7; 3.0; 4.5 and 6.0 dS m-1, with four flow rates of application of the nutrient solution (1.0; 2.0; 3.0 and 4.0 L min-1); in experiment I - sodium water, NaCl was used in the preparation of the nutrient solution, using the treatments described, in order to test the technical feasibility of using this water, with the application rates of the solution. In the following cycles, experiment II and III, only the ionic nature of the nutrient solution was changed, the solution being prepared by adding CaCl2 in experiment II and NaCl; CaCl2; MgCl2 in a 2 : 1: 1 ratio, in experiment III, simulating brackish waters. Physiological and photosynthetic variables were evaluated in the context of gas exchange, aspects of growth and biomass production. Liquid photosynthesis was more sensitive to salinity when the plants were exposed to calcium and mixed water, with carotenoids being the photosynthetic pigment most sensitive to the increase in salinity of the nutrient solution. Reductions in the growth parameters of the crop, due to saline stress, make the commercialization of coriander unfeasible from the level 3.0 dS m-1, due to the deleterious effects observed in the leaves. Increasing the flow to levels greater than 2 L min-1 is not recommended when using brackish water to prepare the nutrient solution. The data obtained were submitted to analysis of variance by the F test and when a significant effect was found to the regression analysis and the Tukey test at 5% probability.