Author(s): SANTOS, M. G. B. dos; COSTA, C. R.; MENDES, G. de O.; PAIVA, A. B.; PEIXOTO, L. S.; COSTA, J. da L.; MARCHI, G.; MARTINS, E. de S.; FIGUEIREDO, C. C. de

Summary: Sewage sludge biochar (SSB) exhibits higher phosphorus (P) concentrations than the original sewage sludge (SS) and can be used as a P fertilizer. However, SSB-associated P is strongly retained in chemical compounds, which hinders its release and subsequent plant uptake. The use of organic acids facilitates P solubilization from SSB. Herein, we evaluated the effect of oxalic acid on P release from SSB applied to soil over time. Biochar was produced at 300 ?C (SSB300) and 500 ?C (SSB500). P release from SSB increased with an increasing concentration of oxalic acid in the SSB incubation solution and in SSB-treated soil. P speciation in SSB showed that P was predominantly inorganic (Pi), which represented 81% and 92% of the total P in SSB300 and SSB500, respectively. Pi in SSB consisted mainly of non-apatite P, accounting for 91% and 96% of all Pi in SSB300 and SSB500, respectively. Because SSB is predominantly insoluble in water, oxalic acid is crucial for the release of P from SSB. Oxalic acid increased P release from SSB300 and SB500 by 103- and 600-fold, respectively, compared to the control, from which P was extracted with water. Oxalic acid enhancement of Prelease from SSB increases the possibility of using SSB as a sustainable source of P for agriculture.

Publication year: 2024

Types of publication: Journal article

Unit: Embrapa Cerrados

Keywords: Adubo de Esgoto, Biocarvão, Fertilizante Fosfatado, Ácido Oxálico