Effects of Plant Biostimulant Humic Acid on the Fruit Quality of Peach

Humic acid is a plant biostimulant that promotes crop growth and improves fruit quality. However, its effects on peach fruits remain unknown. Therefore, this study assessed the effects of humic acid on the peach fruit quality using tap water as the control. The 900-fold dilution of humic acid increased the fruit transverse diameter, single fruit weight, and solid-acid ratio of peach fruits. The 120 and 1500-fold dilutions of humic acid decreased the vitamin C content but increased the titratable acid content of peach fruits. In addition, the total soluble solid content in the 900, 1200, and 1500-fold dilutions of humic acid groups was increased. The maximum sugar components, including the total soluble sugar, sucrose, fructose, and glucose in peach fruits were recorded in a 900-fold dilution group. Moreover, correlation, principal component, and cluster analyses revealed that the fruit transverse diameter, total soluble sugar content, single fruit weight, glucose content, sucrose content, fructose content, solid-acid ratio, total soluble solid, and fruit longitudinal diameter were closely related. In contrast, the vitamin C content, fruit shape index, and titratable acid content were independent. These findings imply that humic acid can be used to improve the quality of peach fruits