Effect of Various Enriched Biochars and PSB on Phosphatase Activity, Phosphorus Availability, and Wheat Growth in Saline Soils Around Lake Urmia

The productivity of plants is adversely affected by soil salinity. However, it is predicted that plant growth-promoting rhizosphere bacterial (PGPRs) and the use of crop residues as biochar can improve plant growth and development in the presence of salinity and different stresses. A pot experiment was performed in a complete randomized design using two soils with different EC (S1 = 2, S2 = 15 dSm-1). Treatments included different types of enriched biochar (BC) as rock phosphate-biochar (BC-RP), BC-H3PO4-RP, BC-HCl-RP, BC-PSB and BC-RP-PSB to assess the effects of apple-grape pruning biochar, enriched biochar, and phosphate-solubilizing bacteria (PSB) isolated from saline soils around Lake Urmia on the phosphorus (P) availability. After harvesting, soil physicochemical properties (pH, EC), P-Olsen, acid, and alkaline phosphatase activities, and plant growth indices were investigated. The results showed that in both soils, the highest alkaline phosphatase activity was in BC-H3PO4-RP and BC-HCl-RP treatments. In both soils, the highest plant dry matter was obtained in BC-H3PO4-RP and the highest plant P in BC-H3PO4-RP, BC-HCl-RP, and BC-RP-PSB treatments. Experimental treatments did not affect the soil EC but significantly reduced the pH of soils. Indeed, BC-H3PO4-RP reduced the pH of S2 and S1 soils by 1.1 and 0.6 units, respectively, while BC-HCl-RP reduced the pH of S1and S2 soils by 0.56 and 1.16 units, respectively. The P-Olsen concentration of S1 soil under BC-H3PO4-RP and BC-HCl-RP treatments were 57.7 and 41 mg kg-1and of S2 soil were 67.4 and 38.6 mg kg-1, respectively. Interestingly, in both soils, P-Olsen concentration in BC-RP-PSB treatment was more than TSP treatment, suggesting a remarkable ability of the studied bacteria. Since enriched biochar with various minerals and inoculation with PSBs showed an unexpectedly higher P-Olsen compared to TSP, more field studies are needed for supporting as well as clear understanding of P-enriched biochar potential in different soils and climates.