Long-term biochar application influences phosphorus and associated iron and sulfur transformations in the rhizosphere

The effects of long-term biochar application on soil phosphorus (P) flux across the root-soil interface and its availability in the rhizosphere of rice (Oryza sativa L) remain unclear. We used diffusive gradients in thin films (DGT), laser ablation-inductively coupled plasma mass spectrometry, and planar optode sensor techniques to characterize, in-situ, the 2D heterogeneity and dynamics of rhizosphere soil P, iron (Fe), sulfur (S) and trace element fluxes, dissolved oxygen and pH in paddy soil, after 10 years of biochar application. Compared to the control (no biochar applied), biochar applied at 4.5, 22.5 and 45.0 Mg ha−1 yr−1 decreased rhizospheric P fluxes by 11.6 In-situ 2D imaging of rice rhizosphere P, Fe, S, and trace elements was elucidated. Long-term biochar application conspicuously lowered rice rhizosphere available P. Soil P release process was related to Fe and S redox status.