Evaluation of Growth Characteristics, Yield, Marketability and Nitrate Levels of Lettuce (Lactuca sativa L) Cultivars Produced in South Louisiana

Abstract

Lettuce (Lactuca sativa L.) is an important leafy vegetable crop grown in worldwide food systems with the United States ranking second behind China in total production. In 2009 the USDA Food Economic Research Service reported 1,057,715 hectares of lettuce grown in the world. Lettuce is a common market crop grown across the United States. Nitrate (NO3-) accumulation in lettuce and other leafy vegetables has been found to be a potential health threat and when consumed by humans, potentially causing methaemoglobinaemia and other diseases. There are four main types of lettuce and numerous cultivars within each type. Fresh weight yields and nitrate accumulation may vary significantly between lettuce types and/or cultivars, 45 cultivars of lettuce, representing the four types, were grown in the field under best management practices at the LSU AgCenter Botanic Gardens in Baton Rouge, LA, during Fall 2011 and Fall 2012. Based on field weight, recommended butterhead cultivars were ‘Caliente’ (21.6 ppm) and ‘Harmony’ (13.9 ppm). The recommended green leaf varieties were ‘Salad Bowl’ (10.6ppp) and ‘Tango’ (14.6 ppm). The recommended red leaf cultivars were ‘Red Salad Bowl’ (15.2 ppm), ‘Red Sails’ (15.4 ppm), and ‘New Red Fire’ (24.0 ppm). The recommended Romaine cultivar was ‘Green Towers’ (11.2 ppm) and the recommended crisphead varieties were ‘Raider’ (17.6 ppm) and ‘Ithaca’ (14.9 ppm). When comparing the highest yielding cultivars from the field weight study, ‘New Red Fire’ (24.0 ppm) produced the highest nitrate concentration in both years 1 and 2. It made up 3.9% of the RfD (EPA’s maximum acceptable oral dose of a toxic substance) for men and 4.59% of the RfD for women. This shows no concern for men or women in the 20-74 age group.