Effect of biostimulants on quality of baby leaf lettuce grown under plastic tunnel

Applications of biostimulants might be used for stimulating the nutrient use efficiency and improving quality of baby leaf vegetables. The aim of this work was to evaluate the use of biostimulant for reducing the nitrate content and improving the commercial quality. The field trials were performed under plastic tunnel in the North Italy vegetable production area (Bolgare, BG, Italy) during spring (April- May) and summer (July). The application of biostimulant (Actiwave®, Valagro S.p.a) was performed by spray using a modified fertigation machine. The concentrations of Actiwave applied were 0, 3, 4.5 or 6 ml m-2. The effect of treatments was evaluated by the following determinations: yield, leaf nitrate content, total chlorophyll, total carotenoids, anthocyanins and total phenols content. In additional the health status of leaves was determined by chlorophyll a fluorescence measurements. Results obtained showed that the 4.5 and 6 ml m-2 Actiwave significantly increased the yield. The leaf nitrate content ranged between 900 and 1100 mg kg-1 FW and was slightly lower in the 3 ml m-2 treatment. The highest chlorophyll and carotenoids were found in lettuce treated with 6 ml m-2 Actiwave concentration. The anthocyanins and total phenols were slightly higher at higher concentration of bistimulant. Actiwave treatments did not affect the main chlorophyll a fluorescence parameters. This result might be due to an increase of light use efficiency in treated plants. In conclusion, the biostimulant was able to increase the yield, but slightly effect on nitrate metabolism was observed. The low leaf nitrate content in all treatments might be due to the optimal environment conditions.