The experiment was carried out in Brasilia, Brazil, from January to March 2004, aiming to evaluate the level of nitrate in lettuce, cv. Veronica, as a result of fertilization, harvesting time and storage period (8ºC). We used the ramdomized blocks experimental design in a factorial 5 x 4 x 4, with four replicates. The five fertilization treatments tested were: 1,5 kg m-2 of chicken manure (T1); 3,0 kg m-2 of cattle manure (T2); mineral, as a result of soil chemical analysis - M (T3); M with 1,5 kg m-2 of chicken manure (T4); and M with 3,0 kg m-2 of cattle manure (T5). The harvesting times were 7 and 11 a.m., and 3 and 6 p.m. The storage periods were 0; 3; 5 and 7 days. The treatments T1 and T4 resulted in plants with the highest levels of nitrate, 1240,12 and 1303,66 mg NaNO3 kg-1, respectivelly, while T2 resulted in the lowest nitrate level, 547,26 mg NaNO3 kg-1. However, when cattle manure was added to M (T5), an increase of 2,18 times was observed in the nitrate level (1195,25 mg NaNO3 kg-1). Plants harvested at 7 a.m. showed the lowest levels of nitrate, suggesting that it is the best moment to harvest lettuce in the Distrito Federal region. During the storage period of seven days, nitrate level was reduced by 29,3%.
Lactuca sativa L.; protected cropping; fertilization; production; refrigeration; quality
