IRRIGATION AFFECTS POSTHARVEST DISCOLOURATION AND YIELD IN ICEBERG LETTUCE

Fresh produce is highly perishable and significant wastage can occur from producer to consumer. Lettuce heads and other leafy salads can often suffer non-infectious discolouration disorders, such as pinking. Pinking of lettuce butts and leaves can occur within only a few days of harvest, and this can limit product shelf life and contribute to retail consumer dissatisfaction. It has already been shown that preharvest water stress can have an impact on the yield and postharvest quality of ‘Batavia’ lettuce. Our aim was to investigate the sensitivity of ‘Iceberg’ lettuce to water stress pre- and postharvest. A lettuce crop was grown in a polytunnel at Harper Adams University; soil was amended with peat to give two defined uniform soil types; 25% (high OM soil) or 5% (low OM soil) in containers of 180 L volume. By alternating the amount of irrigation a range of different water stress treatments were imposed. Increased irrigation led to greater biomass production, with heads containing a greater proportion of water. Analysis also showed that soil type and irrigation significantly affected the total amount of N (%) in lettuce head dry matter, whilst postharvest scoring revealed that the pinking score after 20 days in cold storage was significantly greater in treatments with increased irrigation.