Preharvest application of biostimulants to improve growth, quality, and yield of blueberry (Vaccinium corymbosum L.)

Blueberry production and fruit quality face increasing challenges under current climate change scenarios. Therefore, sustainable strategies such as the use of biostimulants, which have shown beneficial effects that enhance productivity and quality, are needed. This study evaluated the effect of foliar and drench preharvest applications of biostimulants on the growth, yield, and fruit quality of blueberry. The experiment was conducted using plants grown in coconut fiber under greenhouse conditions in a randomized factorial design with three factors: biostimulant, application method, and application dose. The biostimulants tested included melatonin, salicylic acid, glutamic acid, silicon, and yeast extract, applied biweekly from anthesis to fruit maturity. Growth parameters, yield, size, color, and quality traits were measured. The drench application of 100 µM melatonin resulted in the highest yield and plant height, whereas stem diameter increased mainly with 100 µM foliar melatonin. Foliar application of 1000 mg L⁻¹ glutamic acid significantly enhanced the SPAD index. Fruit weight, width and height were superior under 4 mM salicylic acid applied via drench and 500 mg L⁻¹ glutamic acid applied foliar. The width/height ratio reached its highest value with 100 µM foliar melatonin. Foliar silicon at 5 g L⁻¹ increased fruit lightness, while 3 g L⁻¹ yeast extract applied via drench enhanced chroma, with no significant differences in hue. All biostimulants improved fruit firmness; additionally, foliar silicon increased total soluble solids, and 10 g L⁻¹ yeast extract applied foliar enhanced anthocyanin content. Biostimulants applications improved growth, yield, and fruit quality, supporting their potential for sustainable blueberry production.