Yield and quality responses of cos lettuce to organic fertilizers in greenhouse cultivation

The research occurred in a plastic greenhouse in the autumn season between 2022-2023 and 2023-2024. Lettuce was grown in the greenhouse with organic agriculture-origin fertilizers. The cos type lettuce cultivar ‘Presidential’ was used. The aim was to evaluate the effects of various fertilizer applications, including seaweed, vermicompost, humic-fulvic acid, and a control, on lettuce yield and quality. Fertilizers were applied to the soil in liquid form at the recommended rates for lettuce production. The study revealed significant variations in several parameters across applications. Total yield ranged from 21.42 to 43.75 t ha-1, while market yield varied between 20.50 and 41.33 t ha-1. Marketable plant weight ranged from 410.00 to 826.67 kg plant-1, while the average plant weight was between 428.33 and 875.00 kg plant-1. Additionally, the number of discarded leaves ranged from 5.00 to 24.33 units. The SPAD value showed a range of 27.18 to 38.30, while water-soluble dry matter (WSDM) and dry matter values varied between 0.80-4.90% and 3.63-10.15%, respectively, depending on the applications. The study found that the applications generally yielded better results than the control application. In addition, the highest yield and plant weight were observed in lettuce plants treated with seaweed fertilizer.