In an ongoing effort to provide science-based answers to production-related issues, cultivar variety trials were conducted to support the vegetable industry in Alabama. Recent evaluations resulted in guidelines for lettuce cultivar selection in conventional production systems.

The lettuce cultivar trial was conducted during spring 2022 and evaluated 16 lettuce of cultivars (table 1) grown under an open-field system using conventional management practices (figure 1). The field is located at Auburn University’s E. V. Smith Research and Extension Center in Shorter, Alabama.

Crop Management Practices

• Planting date: Seeds were planted into 200-cell trays filled with soilless media on April 4, 2022, and greenhouse grown until transplanting.
• Transplanting date: May 06, 2022
• Bed-spacing: 6 feet center to center
• Row-spacing: 16 inches within bed
• In-row plant spacing: 9 inches
• Plant population: 19,360 plants/acre
• Harvest date: June 7, 2022
• Irrigation: Irrigation water was applied using a drip system installed under white plastic mulching. Irrigation events supplied approximately 1 to 1.5 inches of water per week.
• Fertilizer: Approximately 500 pounds/acre of 10- 10-10 fertilizer was applied preplant using a fertilizer spreader (50 pounds of nitrogen/acre) before laying plastic mulch. A week after transplanting, plants were fertilized once a week until harvest through drip irrigation with 15 pounds of nitrogen/week/acre using 20-20-20 (60 pounds of nitrogen/acre).
• Pest management: Crop management practices for disease, insect, and weed control followed recommendations of the Alabama Cooperative Extension System or the “Southeastern US Vegetable Crop Handbook.”
• Data collection: At harvest, lettuce heads were cut at the base of the plant, and lettuce weight was recorded for calculation of total yield (pounds/acre). Lettuce head diameter (inches) and height (inches) were also recorded from five marketable heads. All data was used for statistical analysis and cultivar comparison within each system. Statistical analysis was performed using the RStudio software using the Fisher’s Least Significant Difference Test with a p-value of 0.05.

Results

Lettuce head weight was the highest for cultivar Bluerock (0.74 pounds) and lowest for cultivar Salanova Red Butter (0.22 pounds). Head diameter was the largest for the cultivars Bluerock (12.0 inches) and Coastal Star (12.0 inches) and lowest for the cultivar Salanova Red Butter (5.0 inches). Head height was highest for the cultivar Bluerock (13.0 inches), and the lowest was Salanova Red Butter (7.6 inches). Overall, lettuce cultivars performed well during the growing season. Particularly, cultivar Bluerock had the highest head weight, head diameter, and head height and can be an option for growers selling lettuce under contracts. Growers selling lettuce per unit (head based) should select cultivars according to costumer demand.

Sthefani de Oliveira, Research Assistant; Raira Pelvine, Research Assistant; Camila Rodrigues, Extension Specialist, Assistant Professor; Chip East, Regional Extension Agent; and Andre da Silva, Extension Specialist, Assistant Professor, all in Horticulture with Auburn University

New January 2023, Lettuce Cultivars for Open-Field Conventional Systems, ANR-2965