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