Effect of fertilizing with potassium sulphtae and iron chelate on nutrient uptake and vegetative traits of Red Delicious apple

Fertilization is one of the most important management tools in horticulture playing an important role in nutrition of fruit trees in order to improve the yield and quality. A factorial randomized complete block design experiment with 3 replications was conducted to investigate the effects of potassium sulphate (0, 50, 100 and 150 g/tree) and iron chelate (0, 10, 20 and 30 ml/tree) during Red Delicious apple tree growth. Some traits including branch length, chlorophyll index, fruit length and width, fruit weight, fruits number, leaf area index and concentration of some nutrients in leaves were measured. The results showed that potassium sulfate and iron chelate improved all growth traits. Potassium sulfate and iron chelate showed a positive and significant increase in yield. With increase in concentration of potassium sulfate, the amount of phosphorus and potassium in leaves was increased, while iron chelate decreased the amount of phosphorus. The highest amount of magnesium was observed in the absence of potassium sulfate treatment and treatment with 30 cc of iron chelate. The highest amount of iron was observed in the case of treatment with 20 and 30 cc of iron chelate with no potassium sulphate application. Also, with the application of potassium sulfate fertilizer, the amount of calcium and copper in the leaves was decreased. Fertilization had no significant effect on the concentration of nitrogen, zinc and manganese in the leaves.