Nitrate concentration and nitrate/ammonium ratio on lettuce grown in hydroponics in Southern Amazon

Lettuce has a predisposition to nitrate accumulation and led many researchers develop research reduce this accumulation. The objective of study was evaluate the effect concentration (NO3-) nitrate/ammonium ratio (NO3-:NH4+) on growth, production these nitrogen compounds in lettuce grown hydroponic system southern Amazon. There were performed two experiments with Iceberg type, floating-hydroponic under protected cultivation. In first experiment, five concentrations (2.5, 5.0, 7.5, 10.0 15.0 mmol L-1) evaluated. second best NO3- : NH4+ evaluated proportions 0:100, 25:75, 50:50, 75:25 100:0 nutrient solution. At 35 days after transplanting, evaluations performed. solution containing (N) as source L-1 contributed higher productivity, being recommended for It is use about 23% N ammonium form, where N-ammonium are not indicated Icebeg type because it reduces productivity green leaf vegetable, causing toxicity symptoms. Key words: Nitrogen, solution, food security.