Nutrient Density in Lettuce Cultivars Grown with Organic or Chemical Fertilization with Elevated Calcium Concentrations, Poster Board #161

This research addresses the potentials for increasing calcium (Ca) concentrations in vegetables. Calcium is a major element for human nutrition, and a diet including Ca-rich vegetables will help in human nutrition. This study explored the potential to increase calcium density of lettuce (Lactuca sativa L.) through cultivar selection and nutrient management. Eighteen cultivars including butterhead, romaine, and loose-leaf phenotypes of heritage and modern genetics were tested in a greenhouse experiment.  Organic fertilizer [3–0.7–3.3 (N–P–K)] and commercial chemical fertilizer (20–4.4–16.6) factored with three elevated calcium levels (50, 100, 200 mg/L as CaCl₂) were the fertilizer regimes. Calcium in whole shoots was analyzed by atomic absorption spectrophotometry of oven-ashed samples. Heritage cultivars had a significantly higher Ca concentration (1.90% dry wt) than modern cultivars (1.57% dry wt). Loose-leaf phenotypes had the highest Ca concentration (2.06%) followed by butterhead (1.66%) and romaine (1.49%).  Accumulation of Ca was higher with the chemical fertilizer (1.90%) than with the organic fertilizer (1.58%). Elevated Ca level in the fertility regimes raised the Ca concentration in lettuce from 1.56% at 50 mg/L to 1.86% at 100 mg/L and 1.79% at 200 mg/L. Large differences in Ca concentration occurred among individual cultivars with ranges from 3.05% to 1.27% Ca. ‘Salad Bowl’, ‘Red Deer Tongue’, ‘Buttercrunch’, and ‘Bronze Mignonette’ were the top in cultivar ranking with mean Ca concentration of 2.50%, whereas ‘Adriana’, ‘Australe’ ‘Coastal Star’, and ‘Forellenschluss’ were low accumulators with a mean of about 1.33%. Fresh wt of cultivars had no correlation with Ca concentration. This experiment notes that selection of nutrient regimes and cultivars can be utilized to manage Ca accumulation in lettuce.