Influence of cultivar, microbiological fertilizers and growing seasons on nitrate content in lettuce

Abstract

Lettuce belongs to a group of leafy vegetable crops with special importance in humannutrition. Along with healthy compounds lettuce can accumulate nitrate in leaves. Thepurpose of this study was to examine the effects of genotype, microbiological fertilizers andseason on plant weight and nitrate content in outer and inner leaves. Green cultivars(′Kiribati′, ′Aquino′, ′Aleppo′) were cultivated in a fertile soil, in a greenhouse trial at thecompany Iceberg Salat Centar, during three successive seasons (autumn, winter and spring).Microbiological fertilizers (EM Aktiv, Vital Tricho and combination of EM Aktiv and VitalTricho) were applied in the soil before trials and foliar. In spring cultivar ′Aquino′ showed thehighest head fresh weight (360.3 g). All microbiological fertilizers led to increased head freshweight in ′Aquino′ during autumn trial. Mainly fresh weight was higher in spring and wintercompared to autumn. Cultivar ′Aquino′ showed the highest nitrate content (985.4 mg/kg,autumn) in outer leaves with application of Vital Tricho. Opposite to that, the lowest nitratecontent was found in inner leaves of cultivar ′Aleppo′ (35.4 mg/kg, spring) with combinationof fertilizers. Generally, microbiological fertilizers significantly increased nitrate content inouter and decreased in inner leaves. In both leaves the lowest nitrate level was measured inspring season. During all trials nitrate content remained under allowed level of EuropeanCommission Regulation (563/2002) for protected lettuce.