Abstract

Soilless cultivation of lettuce gained popularity in recent years in South Africa because of improved yield and quality. Thirteen crisphead lettuce cultivars were evaluated in a gravel-film production system during the winter season at the experimental farm of the ARC-Roodeplaat. The experiment was laid out as a randomized complete block design with five replicates. For each cultivar, yield, internal quality, compactness, uniformity, ribbing, tip-burn, disease tolerance, bolting tolerance and number of days to maturity were recorded. The cultivars were ready for harvest from 70 - 77 days after transplanting. Results showed clear differences between cultivars, with four cultivars, namely Del-Rio, Patagonia RZ, Winter haven and Winter Supreme, out yielding the rest of the cultivars included in the trial. These four cultivars were also more tolerant to tipburn and disease, compared to most other cultivars included in the trial. Cultivars Annie, Del Rio, Supreme Plus and L425 showed the best core ratio, combined with a good colour and tip burn resistance. Results, thus, indicate that variability in yield and quality of crisphead lettuce are determined by cultivar differences, changes in environmental conditions, as well as different production systems utilized by farmers. Improved yield and quality can be obtained by selecting the correct cultivars for winter production in a soilless medium. 

Key words: Gravel-film technique, quality, yield, growing season.