Influence of Spraying of Humic Acid on Shelf Life and Postharvest Quality of  Granny Smith Apple

In order to investigate the influence of humic acid spraying on trees on shelf life and to maintenance of quantitative and qualitative characteristics of ‘Granny Smith’ apple, an experiment based on completely randomized block design was conducted in khoramdareh postharvest physiology laboratory of University of Zanjan. The humic acid spraying was conducted in four concentrations of 0 (distilled water), 5, 10 and 15 mg l-1 on 8 year-old ‘Granny Smith’apple trees grafted on MM106 rootstock. Spraying was conducted 2, 4 and 8 weeks after full bloom stage. Fruits of trees treated stored in 0±0.5°C with 90±5% relative humidity for six months. Fruit weight loss, fruit firmness, pH, total soluble solid (TSS), titrable acid (TA), total sugar (TS) and ascorbic acid content (vitamin C) were measured every two months. The results showed that, during the storage, fruit weight, fruit firmness, TA and ascorbic acid decreased. The maximum and minimum amont was belong to 10 and 15 mg l-1 humic acid and control treatment in the third stage of sampling (sixth months). Meanwhile, total soluble solid, pH and TA increased in the storage. According to the obtained results, it can be concluded that humic acid spraying had influence on shelf life and quantity and quality characteristics of ‘Granny Smith’ apple during storage. Therefore, to maintain postharvest quality of ‘Granny Smith’ apple spraying of humic acid with concentrations of 10 and 15 mg l-1 on trees is recommended.