Effect of Humic Acid Water‐Soluble Fertilizer on Quality of Loquat Fruits

Humic acid is a byproduct of the decomposition of organic matter and plays a crucial role in promoting plant growth and development. In order to improve the quality of loquat ( Eriobotrya japonica (Thunb.) Lindl.) fruits, the effects of humic acid water‐soluble fertilizer (1600−, 1300−, 1000−, and 700−fold dilutions) on the quality of loquat (’Dawuxing’ variety) fruits were studied. Compared with control, the 1000−fold dilution resulted in a 26.49% increase in the single fruit weight of ripe fruits at the mature stage. Compared with control, the 1600− and 1300−fold dilutions increased the total soluble sugar content in the ripe fruits by 21.25% and 18.58%, respectively. Additionally, compared with control, the 1600−, 1300−, and 1000−fold dilutions reduced the total organic acid content in the ripe fruits by 16.77%, 21.50%, and 13.73%, respectively. The vitamin C content in the ripe fruits was lowest at the 1000−fold dilution, with a 56.84% decrease compared with that of control. Compared with that in control fruits, the total flavonoid content in the ripe fruits decreased by 23.86% at the 700−fold dilution. However, the contents of carotenoids and total phenols were not affected by humic acid water−soluble fertilizer. Furthermore, humic acid water−soluble fertilizer increased the content of each sugar component, sweetness value, and sugar/acid ratio of ripe fruits while reducing the content of each organic acid component except quinic acid. Therefore, humic acid water−soluble fertilizer can improve the quality of loquat fruits, especially at appropriate concentrations of 1300− to 1000−fold dilution.