Silicate fertilization contributes to the postharvest conservation of lettuce

Abstract

The importance of silicate fertilization in postharvest conservation has been confirmed in some vegetables, such as radish, arugula and tomato. However, there is still a lack of further information on the effect of this element on postharvest conservation in lettuce. Thus, the objective of this work is to investigate the use of different doses of potassium silicate in the postharvest conservation of curly lettuce, grown in a protected environment. For this, lettuce seedlings, Lactuca sativa L., curly variety, cultivar “Vanda”, were cultivated from March 20th to May 5th, 2024, in plastic pots containing 5 dm3 of substrate inside the greenhouse of the Federal Institute of Santa Catarina (Instituto Federal Catarinense), Campus Videira. The plants grew with the substrate kept close to the field capacity until the end of the experiment, lasting 45 days. Irrigation control was carried out by the gravimetric method (daily weighing of the pots), adding water until the mass of the pot reached the previous value determined, considering the mass of the soil and water. The application of potassium silicate doses was carried out through a manual sprayer with a capacity of 500 mL and a fan-type nozzle for application. Control plants in which Si was not applied were sprayed with distilled water. The simple foliar mineral fertilizer, potassium silicate (Flex Silicon^®), was used at the doses: 0 (Control), 3.0 and 6.0 ml/L of potassium silicate, applied every 10 days after transplanting the seedlings to the pots. The experiment was set up in a completely randomized design, in split-plots in time [0, 3, 6 and 9 days after harvest – storage period], consisting of three doses of silicate fertilization [0, 3 and 6 ml/L of potassium silicate], with four replications. Each experimental unit was composed of a plant packed in low-density polyethylene bags. The plants were conditioned in a vertical refrigeration unit, maintaining an average temperature of 5ºC, for 9 days. The following variables were evaluated: Chlorophyll a, b and total levels; the plant's fresh matter, titratable acidity, pH and postharvest visual quality. The data were submitted to analysis of variance and the treatments were compared by Tukey's test (5% probability), using the R^® software program, version 4.3.2. According to the results obtained, it was observed that silicate fertilization contributed to the preservation against oxidative damage, in the maintenance of chlorophyll contents and fresh mass of the plants, providing delay to senescence and, consequently, a better postharvest conservation of lettuce, especially at the dose of 6.0 ml/L of potassium silicate. However, the application of potassium silicate did not affect the titratable acidity and pH of lettuce throughout the storage period.