Bone char: characterization and agronomic application as an alternative source of phosphorus

ABSTRACT Alternative materials can be used to reduce reliance on mining for P-based fertilizers. In this sense, the pyrolysis process of bovine bones produces the “bone char”, which can be used as a source of P. This study aimed to characterize bone char and conduct a comparative analysis with both soluble (triple superphosphate) and non-soluble (Bayóvar phosphate rock) phosphate fertilizers, specifically examining its behavior in soil and uptake by plants. Bone char characterization was performed by X-ray diffraction (XRD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy coupled with energy-dispersive (SEM-EDS). The XRD analyses have shown the presence of hydroxyapatite in the bone char, bands assigned to P-O stretching from phosphate have been observed in ATR-FTIR, and Ca, P, C, and O elements were identified in the materials by EDS analyses. Solubility from fertilizer extractants was higher for bone char compared to Bayóvar, and both sources showed lower solubility compared to triple superphosphate. Cumulative amount of P released from bone char was higher than Bayóvar and lower than triple superphosphate. Amount of total dry matter, total shoot P uptake, and total shoot Ca uptake were higher for triple superphosphate compared to bone char and Bayóvar. Release profile of P from bone char strongly suggests this material can be used as a slow-release P source, with intermediate solubility between soluble and non-soluble commercialized sources.