Effect of the use of biostimulants on the yield and quality of tomato (Solanum lycopersicum L.) grown in a greenhouse

Tomato (Solanum lycopersicum L.) is among the most important horticultural crops globally, and interest in improving both yield and quality through sustainable strategies is increasing. This study assessed the effects of a biostimulant based on humic acids and microorganisms on the yield and organoleptic quality of two saladette tomato varieties (Macizo and Moctezuma) under greenhouse conditions. A randomized complete block design with four replicates compared control treatments (CT) without biostimulant to biostimulant treatments (BT). Biostimulant application significantly increased yield in both varieties (p<0.05), with Macizo rising from 27 to 37.5 kg/plant (39%) and Moctezuma from 28.5 to 42 kg/plant (47%). Quality improvements included greater equatorial diameter in Moctezuma and increased firmness in Macizo (p<0.05). After 14 days at 19 °C, BT fruits lost significantly less weight than CT fruits. Flavonoid content increased in BT (Macizo: 4.46 vs 1.48 mg QE/100 g; Moctezuma: 3.36 vs 1.25 mg QE/100 g), while antioxidant activity and total phenolics decreased (p<0.05). No differences were found in color, soluble solids, or titratable acidity (p>0.05). These results indicate that biostimulants can enhance tomato yield and some quality traits, but their influence on secondary metabolites may differ depending on variety and cultivation conditions.