Effect of different sources of sulfur on distribution of inorganic phosphorus forms in a calcareous soil

In order to study the effect of different sources of sulfur on inorganic phosphorus fractions in a calcareous soil, an incubation experiment was conducted in a completely randomized design with five treatments in three replications. Treatments were including: control (without sulfur compounds), Al2(SO4)3, FeSO4, S + Ti (sulfur + thiobacillius) and H2SO4 at 2% (w/w). Amendments were incubated at 25±1 °C for a period of 12 days. Then, available-P (Olsen-P) and different forms of inorganic phosphorus were determined by sequential extraction method. The application of sulfur compounds caused significant changes (p≤0.05) in the amount of P-Olsen and inorganic forms of phosphorus (Ca2-P, Ca8-P, Al-P, Fe-P, Ca10-P) compared to control. The amount of available phosphorus in H2SO4, Al2(SO4)3 and S + Ti compared to control increased 240, 70 and 50%, respectively. Also, these amendments caused to insoluble forms of phosphorus, Ca8-P and Ca10-P, significantly reduced and in more soluble forms of Ca2-P and available-P could be used. In the amendments, FeSO4 caused 30% decrease in available-P and 4% increase in apatite compared to control. The results of correlation studies showed that available phosphorus (Olsen extracted phosphorus) had a significant correlation with Ca2-P, Ca8-P, Ca10-P and residual-P; the results of this study showed the effect of sulfur compounds on the distribution of phosphorus in different forms, so it is expected that Sulfur sources affect the usability and phosphorus chemistry.