Evaluation of sulfur-bentonite granules enriched with iron as replacer of chemical fertilizers in calcareous soils

Extensive use of chemical fertilizers has caused various mounting problems for the environment including pollution of cultivated products, soil and water resources. Calcareous soils face issue of low solubility and availability of nutrient elements for plants which increases use of chemical fertilizers and its environmental consequences. Hence, methods capable of healing such deficiency and decreasing use of chemical fertilizers are vital. Although sulfur-bentonite granules as replacer of mass consuming chemical fertilizers have environmental priority improvement of their efficiency requires further research. Objective of this research is evaluating sulfur-bentonite granules enriched with iron as one of the plants' nutrient elements having broad insufficiency across farmlands in Iran. Therefore, sulfur-bentonite-iron granules compared to sulfur-bentonite alongside with iron powder dispersed into the soil mass throughout simulating real environment by soil columns inoculated with Thiobacillus thioparus were evaluated for 19 two-weeks leaching periods. The results revealed that application of sulfur-bentonite-iron has acceptable effect on iron availability while it brings efficient solubility of sulfate, nitrate and phosphate into calcareous soils.