Hidroponia utilizando águas salobras nos cultivos de agrião e couve chinesa

Abstract

The majority of the groundwater reservoirs in the Semiarido Region present high salt concentrations. However, the scarcity of this resource compels the use of this water to several human activities, including agriculture, which makes it necessary to study techniques which enable the use of these waters. Therefore it was aimed to evaluate the use of brackish groundwater on the growth, yield and nutritional aspects of two oleraceous, watercress and chinese cabbage, through a NFT (Nutrient Film Technique) hydroponic system in a greenhouse. Three strategic situations were used: Experiment I – salinated water from NaCl addition in six levels of salinity (0.2; 1.2; 2.2; 3.2; 4.2 and 5.2 dS m-1), being these waters used to prepare the nutrient solution and to replace the evapotranspirated water volume; Experiment II – simulation of brackish water from five underground wells (T2 – Well located in the community Poço do Boi (PB); T3 – Poço da Pousada (PP); T4 – Well located in Agrovila 8 (PAV8); T5 – Well located in Fazenda Bruaquinha (PFB) and T6 – Well located in the community Sitio Angico (PSA), these waters were used to prepare the nutrient solution and evapotranspiration (ETc) replacement; Experiment III – The waters used cotained the same characteristics from experiment II, but the ETc replacement was made using water supply in all treatments. The experiments were carried out at the Experimental Station of Irrigated Agriculture Prof. Ronaldo Freire de Moura from the Department of Rural Technology (DTR) at UFRPE, Recife/PE, using completely radomized experimental design with six treatments and four repetitions, making a total of 24 experimental parcels to each crop. Both of the crops showed a linear reduction on the variables: leaf area (AF), fresh mass of aerial part (MFPA), dry mass of aerial part (MSPA), absolute growth rate of the fresh mass (TCAMF), absolute growth rate of the dry mass (TCAMS) and relative growth rate of the dry mass) (TCRMS), with the increase in water salinity used in the preparation of the nutrient solutaion and replacemente of the evapotranspirated water film. There was a reduction of 10.45 and 9.67% of fresh mass of aerial part (MFPA) and dry mass of aerial part (MSPA), respectively, for watercress; whereas, for the Chinese cabbage, there was a reduction of 15.3 and 13.95%, according to the increase in water salinity. As for water consumption there was a quantitative reduction with the increase in salinity levels and with the decrease in the grounwater quality from the wells; regarding the nutritional aspects there was an increase in the concentrations of the sodium and chloride ions on the plant tissue with increasing electrical conductivity of the water salinizated with NaCl; as for the condition of the water use, it was found on the leaves high content of the ions with greater concentrations in the water.