This study investigated the effects of different nitrogen mineral fertilizer formulations on the morphological and phytochemical traits of five butterhead lettuce (Lactuca sativa L.) cultivars grown under protected conditions. The experiment was conducted in a greenhouse during the winter–spring growing season. The analyzed cultivars included Genezis, Zeralda, Majska kraljica, Atrakcija, and Nansen. Three types of nitrogen fertilizers—ammonium sulfate, ammonium nitrate, and urea—were applied at a rate of 100 kg N/ha. The observed parameters included head weight, head height, vitamin C content, and nitrate concentration in the leaves. Significant differences were found among cultivars for all analyzed traits. The highest head weight was recorded in the cultivar Genezis, while the lowest was in Nansen. Head height ranged from 10.25 cm (Genezis) to 12.05 cm (Nansen). Vitamin C content varied between 18.88 mg/100 g (Genezis) and 23.55 mg/100 g (Nansen). The highest nitrate accumulation was observed in Majska kraljica, and the lowest in Nansen, with ammonium nitrate fertilization resulting in the highest average nitrate content. The interaction between cultivar and fertilizer type significantly influenced the measured traits, suggesting that each cultivar responds differently to nitrogen fertilization. These findings underscore the importance of selecting appropriate nitrogen fertilizers and cultivars to optimize yield, nutritional quality, and food safety in lettuce production.
Pavlović et al. (Thu,) studied this question.