Impact of burning on carbon stability in soil amended with micro- and nanobiochar

• Grant number: 25/08094-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: July 01, 2025
• End date: February 28, 2026
• Field of knowledge: Physical Sciences and Mathematics - Geosciences
• Principal Investigator: Matheus Bortolanza Soares
• Grantee: Raphael Assumpção Gealorenco da Silva
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

Burning, a common practice in agricultural areas of the Cerrado biome, releases large amounts of carbon (C) into the atmosphere and compromises the soil's ability to function as a carbon dioxide (CO2) sink. The application of biochar, especially in fine fractions, which exhibit higher reactivity and stronger interaction with the soil matrix, emerges as a promising strategy to recarbonize these degraded soils. However, very fine biochar particles may be more susceptible to loss through volatilization or dispersion during subsequent fire events, thereby reducing the effectiveness of the amendment and requiring appropriate management to stabilize biochar in the soil. This study aims to evaluate carbon stability in soils amended with biochar at micrometric and nanometric scales when subjected to simulated burning. The experiment will be conducted using samples from the surface layer of a Yellow-Red Latosol under pasture, incubated for 180 days with micrometric (200¿¿m) and nanometric (< 50¿nm) biochar. Soil samples will be exposed to direct flame from a propane-butane torch to simulate a fire event. After cooling, total and dissolved carbon contents in solution will be quantified. Organic matter pools will be assessed through particle-size physical fractionation, allowing separation between particulate and mineral-associated fractions. Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) will be employed to evaluate the structural quality of organic matter and the thermal alterations caused by fire exposure. Our hypothesis is that thermal stress alters biochar reactivity, particularly in the nanometric fraction, reducing its carbon stabilization capacity. The results of this study are expected to enhance the understanding of the risks and benefits of using biochar in fire-prone tropical soils, guiding more effective carbon sequestration practices in degraded agricultural areas.