Effects of Sulfur Application on Soil pH and Uptake of Phosphorus, Iron and Zinc in Apple Trees

The main reasons for the fixation of some elements and consequently nutrient deficiencies, especially phosphorus, iron and zinc, are high levels of calcium (calcareous soils) and soil pH. Two sulfur fertilizers (sulfur alone and sulfur + organic material + Thiobacillus spp.) with two rates (2 and 4 kg sulfur/tree) were used to decrease soil pH and availability of P, Fe and Zn in apple trees during the growing season. A control treatment with no sulfur was also included in the experiment. The experiment was based on randomized complete blocks design with three replications and was carried out in the apple orchards of the West Azarbaijan province. Results showed that the sulfur treatments had significant effects on soil pH, chlorophyll content of leaves and phosphorus, iron and zinc concentrations of leaves and fruits in apple. On the average, applying sulfur decreased pH of soil and increased the chlorophyll content of leaves, and iron, zinc and phosphorus concentration of fruits in apple by17.09%, 4.8%, 30.24%, 11.61% and 18.76%, respectively, as compared to the control. Regarding the soil pH and other criteria about the nutrients availability and concentration, it seems that the application of 2 kg/tree sulfur fertilizer would be beneficial for apple orchards located in the highly alkaline soils of the area under study.