Comparative Effects of Biostimulants and Fruit Enlargement Agents on Fruit Quality in Two Kiwifruit Cultivars.

Biostimulants have been increasingly investigated as eco-friendly alternatives to synthetic fruit enlargement agents in horticulture. In this study, two commercially cultivated kiwifruit cultivars, Zhongmi No. 2 and Jintao, were used as experimental materials. Three biostimulant products with distinct functional compositions were investigated: Benefit PZ (BPZ), which is rich in potassium humate and organic nitrogen; Shengcai A (SCA), containing amino acids and trace elements; and Puluosaiting (PLST), a natural seaweed extract-based formulation rich in bioactive compounds. Their effects on fruit development and internal quality attributes were compared with those of two fruit enlargement agents, 6-benzylaminopurine (6-BA) and forchlorfenuron (CPPU). Field experiments were conducted in two orchards located in Dancheng and Xixia, Henan Province, China, and treatments were applied during early fruit development. Growth traits (longitudinal and transverse diameters, single-fruit weight and firmness) and quality indicators (Soluble Solids Content, Titratable Acidity and Dry Matter Content) were measured at commercial maturity. CPPU and 6-BA substantially increased fruit size and weight compared with the control, whereas biostimulants produced moderate improvements without excessive enlargement. Notably, biostimulant treatments consistently enhanced internal quality attributes, indicating their potential to improve fruit quality without the drawbacks of excessive enlargement. Environmental and management differences between sites may also have contributed to treatment variability. These results suggest that biostimulants can improve internal quality traits while avoiding excessive fruit enlargement, representing a promising option for sustainable kiwifruit production.