Influence of Ectomycorrhizal Hyphae on Phosphate Fractions and Dissolution of Phosphate Rock in Rhizosphere Soils of Pinus radiata

A study was conducted to determine the effect of ectomycorrhizal hyphae on phosphate rock dissolution and soil properties in the rhizosphere of one-year-old Pinus radiata D. Don seedlings established on an allophanic soil (Andosol) in the field. High and low ectomycorrhizal hyphal activities were produced in soils inside the lower compartments of rhizosphere study containers by using either 26 μm or < 10 μ m pore-size nylon mesh(es) at the interfaces between the lower and upper compartments. The meshes at the interfaces allowed (26 μm) or reduced (< 10 μ m) hyphae penetration into the lower compartment. Pairs of containers, one with 26 μ m mesh and the other with < 10 μ m mesh, were buried under Pinus radiata seedlings for 10 months in a forest plantation. The effect of ectomycorrhizal (ECM) hyphal activity on phosphate rock dissolution and soil properties was determined. The increased ECM hyphal activity induced increased soil acidification and promoted greater production of acid phosphatase enzyme, causing greater changes in phosphorus (P) fractions in the rhizosphere soils. The increased ECM hyphal activity also stimulated higher dissolution of phosphate rock and mobilization of soil organic P. The results suggest that ECM hyphal strand has a significant role in mobilizing low-solubility P forms and soil organic P for utilization by the tree.