Eficiência do uso de águas salobras no cultivo hidropônico da couve-folha

Abstract

The Brazilian semi-arid region in its entire length is characterized mainly by prolonged periods of drought due to rainfall irregularity, which usually remain concentrated in short periods, whereas high rates of evaporation throughout the year promotes a scarcity of surface water. These factors hinder the implementation of agricultural systems that demand large amounts of water, e.g. conventional agriculture. This research focused on generating and improving technology capable of introducing the groundwater of Brazil's semi-arid region into a sustainable economic activity. Hydroponic cultivation system is able to viable the production all year round, thus ensuring regularity in products supply. Based on the premise that hydroponics can be consistent with the exploration of brackish groundwater, the present study aimed to evaluate the efficiency of brackish water use in collard greens production, regarding its technical feasibility. The experiment was carried out under protected environment conditions, using collard greens “Top Bunch”, whose experimental design was performed in randomized blocks with seven replications in 42 plots. Six levels of electrical conductivity water (ECw) were evaluated, namely: 0.3; 1.0; 2.0; 3.0; 4.0 and 5.0 dS m-1, through its use in the nutrient solution production and the replacement of evapotranspiration (ETw). The level 0.3 dS m-1 refers to the control treatment without NaCl addition. The hydroponic system adopted was the NFT (Nutrient Film Technique) in polypropylene gullies with 4% slope. The increase in water salinity promoted a reduction in crop growth, decreasing plant height, leaf area and stem diameter, whereas parameters such as root length, number of leaves, root dry mass, shoot root ratio and leaf hydration level did not show significant statistical differences through water salinity. Regarding the production of cabbage leaf, a reduction of 7,23% in the production of fresh matter accumulated at the end of the cycle was observed for each unit increase of CEa. There were no symptoms that compromised the quality of the crops, which also had its water consumption reduced with the increase of the solution salinity. The Water Use Efficiency based on the fresh matter of the leaves increased with the electrical conductivity of water. In general, the results obtained here demonstrate that it is possible to use brackish water in collard greens cultivation without significant quality losses.