Effect of Enriched Biochar and Phosphate Solubilizing Bacteria (PSB) on the Distribution of Phosphorus Forms in a Saline and non-Saline Soil of Lake Urmia Basin

To study the effect of enriched biochar (EB) by phosphate solubilizing bacteria (PSB) on soil phosphorus (P) fractionation and explain the change in soil phosphorus availability by determining changes in different forms of phosphorus, a factorial incubation experiment in a randomized complete design with six treatments (fertilizer treatments (control (count), biochar (BC), phosphate fertilizer (TSP), Biochar-Rock phosphate (BC-RP), biochar- PSB (BC-PSB) and enriched-biochar with rock phosphate and PSB (BC-RP-PSB) and two soil types with different EC (2 and 15 dS m-1) was studied in saline soils around Lake Urmia. Olsen-P, pH and different forms of inorganic P were determined by sequential extraction method at 7, 30 and 60 days of incubation. The results showed that on average, the BC-PSB-RP and BC-PSB treatments reduced the pH of soils S1and S2 0.1 and 0.4 unit, respectively. BC-PSB-RP treatments reduced Olsen-P of S1 and S2 soils from 6 to35.3 mg.kg-1 and 7 to 41.7 mg.kg-1, respectively. Microbial treatments significantly (p <0.01) altered the distribution and amount of inorganic P forms. BC-PSB-RP reatment increased the amount of Ca2-P fraction in S1 soil by 10 and in S2 soil by 5.2 time. However, the amounts of Ca8-P, Al –P and Ca10-P fractions reduced significantly. Olsen P positively and significantly correlated with Ca2-P, Fe-P, and Ca10-P fractions and suggesting that in the extraction of Olsen-P, phosphorus is released from these mineral fractions. The results showed that the use EB by PSB can provide long-term P supply to plants and had a better effect on increasing the availability of P in saline conditions.