Nitrate and sodium contents on lettuce and drained water as function of fertilizing and irrigation water quality in Brazil

Contamination of plants and waters with nitrate and sodium is an important environmental problem that can affects humans. An experiment was carried out aiming to evaluate the effect of fertilization and irrigation water quality on NO3- and Na+ contents of drained water and lettuce (Lactuca sativa L.) plants in Rio Claro, São Paulo State, Brazil. Treatments were distributed in a factorial arrangement 5 x 2, referring to fertilization and irrigation water quality (treated and polluted water), respectively, with three repetitions. The following fertilizers were used: Biofertilizer (BIO), bovine manure (BM), poultry manure (PM) and mineral fertilizer (MF). Additionally a non fertilized (NF) treatment also was studied. The following variables were registered: a) Drained water: Nitrate and sodium contents and presence of fecal and total coliforms; b) Lettuce leaves: nitrate content. The average nitrate and sodium contents of drained water indicated that contamination slowly advances on soil profile in areas of disposal of organic and inorganic residues. The fertilizer used on lettuce cultivation affected sodium and nitrate contents of leaves and drained water, and, in contrast irrigation water quality had no effect.