Bone Char: Synthesis, 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 can produce a product called “bone char”, which can be used as a source of P. The present work aims to synthesize, characterize, and evaluate the solubility of fertilizers extractants using bone char, Bayóvar, and triple superphosphate; to evaluate the ‘‘in vitro’’ release of P; to investigate the availability of P from the fertilizers in consecutive cultivations of maize and black-oat. The characterization of the bone char 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. The solubility from fertilizers extractants was higher for bone char compared to Bayóvar and both sources showed lower solubility compared to triple superphosphate. The cumulative amount of P released from bone char was higher compared to Bayóvar and lower than triple superphosphate. The quantities of total dry matter, total shoot P uptake, and total shoot Ca uptake were higher for triple superphosphate compared to bone char and Bayóvar. The release profile of P from bone char strongly suggests that this material can be used as a slow-release P source, with intermediate solubility between the soluble and non-soluble commercialized sources.