Zinc accumulation in lettuce cultivars grown with organic or chemical based nutritional regimes

ABSTRACT

This study determined the potential to increase Zn density of lettuce (Lactuca sativa L.) through cultivar selection and nutrient management. Organic fertilizer and Hoagland and Arnon no.1 solution factored with three zinc (Zn) levels provided as zinc sulfate (ZnSO₄) were the fertilizer regimes in a greenhouse experiment. Modern cultivars had a 32% higher fresh head weight than heritage cultivars, but each accumulated the same Zn concentration (65 mg kg⁻¹ dry wt). Butterhead phenotypes had a 38% lower yield than loose-leaf and had the highest Zn concentration (78 mg kg⁻¹ dry wt) followed by romaine (66 mg kg⁻¹ dry wt) and loose-leaf (53 mg kg⁻¹ dry wt). Concentration of Zn did not differ between fertility regimes, being about 66 mg kg⁻¹ dry wt with each regime. Differences in Zn concentrations were significant among individual cultivars with ranges from 42 mg g⁻¹ dry wt to 91 mg kg⁻¹ dry wt. ‘Tom Thumb’, ‘Adriana’, ‘Claremont’, and ‘Focea’ were the top in cultivar ranking, with mean Zn concentration of 63 mg kg⁻¹ dry wt. The results signify that selection of cultivars may be utilized to increase Zn accumulation in lettuce but that nutritional regimes had little effect on accumulation.

KEYWORDS:

• Micronutrients
• zinc accumulation
• nutritional regimes
• Lactuca sativa
• nutrient density

Acknowledgment

This research is a contribution of Projects MAS 963 and MAS 981 of the Massachusetts Agricultural Experiment Station, and paper number is 3498 in the journal series.