Abstract

Assays were carried out on lettuce using different cultivars, nitrogen content of greenhouse soil, and hydroponic nutrient solutions (NFT and float system). Comparison with analyses made on nitrate in samples of lettuce (Lactuca saliva var. capitata) sold in the main markets of Santiago, Chile, was done. The study was carried out during the winters of three consecutive years. Statistical studies for each of the assays were made by use of the minimum significant difference test (DMS). A sulfanilamide spectrophotometric method was used to estimate the nitrate content in leaves. Results showed that the leaf nitrate concentrations in all treatments were under the maximum critical levels required by the European Union (4,500 mg/kg F. W.) for the three winter periods studied. It was also found that the nitrate content was higher in the outer leaves of the lettuce.