Microbiological quality of organic vegetables produced in soil treated with different types of manure and mineral fertilizer

Abstract

An attempt was made to evaluate microbiological quality of horticultural crops grown organically. Three species of vegetables were used, lettuce (Lactuva sativa), radish (Raphanus sativus) and spinach (Tetragonia expansa), grown organically, in fertile soil. Six different treatments were applied: mineral fertilizer, chicken, cow, and pig manure, chicken litter and cow manure, in association with a liquid foliar biofertilizer. These crops were handled according to correct agronomic practices for growing crops organically for commercial purposes. Samples were examined for the Most Probable Number (MPN/g/mL) of total and fecal coliforms and to detect the presence of Escherichia coli and Salmonella spp. All analyzed samples were considered acceptable for consumption, as Salmonella spp. was not detected. However, 63.3%, 50.0%, and 23.3% of the samples of lettuce, radish and spinach, respectively, contained >102 total coliforms/g of product. None of the samples of spinach or radish presented >102 fecal coliforms/g, and only 6.6% of lettuce samples contained >102 fecal coliforms/g. The presence of E. coli was confirmed in one sample of spinach, cultivated with cow manure.