Effect of foliar spraying by humic acid on mineral leaf composition, yield and fruit quality of apple cv.  Granny Smith'

Effect of foliar spraying by humic acid on mineral leaf composition، yield and fruit quality of apple (Malus domestica L. cv. ‘Granny Smith’) was studied. An experiment based on randomized complete design was conducted in Khorramdare city of Zanjan province. Spraying of humic acid was conducted in four levels 0، 5، 10 and 15 mg/l on eight year-old ‘Granny Smith’ apples grafted on MM106 rootstock. Spraying was conducted two، four and eight weeks after full bloom stage. Results showed that humic acid treatment significantly increased yield، total soluble solid (TSS)، acidity (pH)، concentration of leaf potassium and total chlorophyll content. Concentrations of 10 and 15 mg/l had the highest effect on yield. The humic acid treatment reduced vegetative current shoot growth. There have not significant effect on fruit firmness diameter and length fruit of treated fruits and control. The parameters such as total sugar، leaf area، concentration of N and P of leaf did not influenced by humic acid treatment. According to the results، it can be concluded that concentrations of 10 and 15 mg/l of humic acid spraying have main effect on increasing yield and precocity of ‘Granny Smith’ apple.