Effects of Salinity and Plant Density on Quality of Lettuce Grown in Floating System for Fresh-Cut

Quality of fresh-cut lettuce depends strongly on the raw material characteristics. Floating system allows to enhance quality as well hygienic characteristics of raw material. Different researches investigated the effect of nutrient solution EC and plant density on yield and quality of leafy vegetables, while scarce attention was addressed to influence on quality parameters during fresh-cut storage. For this purpose a trial was carried out to evaluate the influence of different EC of nutrient solution and plant density on production, quality and shelf-life of fresh-cut lettuce. Plants of Lactuca sativa var. longifolia 'Xanadu' were grown in floating system adopting three nutrient solutions with different electrical conductivity (2.8, 3.8 and 4.8 mS cm(-1)) and two plant densities (366 and 750 plant m(-2)). At harvest (35 days after sowing) plants (5-6 leaves) were weighed, processed as fresh-cut product and stored at 5 degrees C. Some parameters (respiration rate, dry matter percentage, firmness, colour, chlorophyll and nitrate content) to evaluate the shelf life were determined after 1, 4 and 9 days of storage. Salinity decreased yield and leaf nitrate content and these effects were more evident in the highest plant density. In relation to storage, our results showed the better suitability to fresh-cut processing in product obtained with 3.8 mS cm(-1) EC treatment. Despite the highest yield obtained, the fresh-cut product of plants grown at highest plant density showed large variation of some parameters considered, probably in relation to higher respiration rate.