Investigating phosphorus distribution and availability in presence of organic matter and elemental sulfur along with thiobacillus bacteria in two soils with different texture

Phosphorus (P) is often lacking in calcareous soils. To investigate the effect of organic matter and elemental sulfur (S) on P availability and fractions in two calcareous soil with different textures (Clay ‌loam and Loamy sand) and total iron and aluminum concentrations, incubation studies were carried out for 12 weeks. This study was conducted in the soil science laboratory of Malayer University in 2019. The treatments include the simple treatment of sheep manure (organic matter=OM) (0, and 2 %), S (0, 0.25, and 0.5 %), and integrated treatment of OM and S in the presence of Thiobacillus bacteria. Every week, P concentration in control and treated soils was measured. At the end of incubation period, EC, pH, ECC percentage, gypsum percentage, and inorganic P fractions in control and treated soils were measured, too. At the end of the incubation period, EC and gypsum percentage increased in both treated soils. The presence of OM decreased the gypsum in soils and increased P concentration in the soils. In Clay loam soil treated with 0.25, and 0.5 percent of S, adding OM decreases the rate of P transformation, from 0.226 to 0.153 and from 0.168 to 0.154 mg kg-1 week-1, respectively and in Loamy sand soil caused an increase from 0.129 to 0.161 and from 0.125 to 0.184 mg kg-1 week-1, respectively. In both soils, simple and integrated treatments increased the dicalcium phosphate fraction and decreased the octacalcium phosphate fraction, and the apatite fraction decreased in integrated treatments. In Loamy ‌sand soil, simple and integrated treatments increased the aluminum phosphate fraction. The results showed that integrated treatment of OM with 0.25% of S in both soils increased the P availability, and despite the fixation of P in Loamy ‌sand soil, due to high total iron and aluminum content, OM increased the P availability in Loamy ‌sand soil.