Exogenous labile C application enhances Fe-P utilization for mycorrhizal plants through Iron-Reducing bacteria in subtropical soil

Abstract

In a greenhouse experiment, Medicago sativa was grown in iron-rich soil inoculated with arbuscular mycorrhizal fungi (Funelliformis mosseae, FM) and/or iron (Fe) -reducing bacteria (IRB, Klebsiella pneumoniae strain L17) with three exogenous labile C input forms (no C source, as a single dose, and as a pulse) at rates of P0 and P5 (0 and 5 mg P2O5 kg-1, KH2PO4), which is to understand the role of IRB in enhancing the Fe-P utilization with exogenous labile C in subtropical soil. The results showed when inoculated with IRB, labile C as a pulsed input significantly improved the mycorrhiza colonization and hyphal length density, and increased the shoot P content, microbial biomass C and glomalin content at P5 rate; meanwhile, the labile C input also promoted the Fe(II) production, when inoculated with IRB, labile C as a pulsed input increased the C/A extractable Fe(II), oxalateextractable P and microbial biomass P content. These facts suggested that application of labile C as a pulsed input enhanced the ability of IRB in improving the Fe reduction and Fe-P utilization in subtropical soil.