Detailed mapping of hematite and goethite in Brazilian soils using spectral data and machine learning

• Grant number: 23/13708-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: November 01, 2023
• End date: October 31, 2024
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: José Alexandre Melo Demattê
• Grantee: Fernando Yutaro Makino
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated research grant: 21/05129-8 - The Brazilian soil quality determined by geotechnologies: mapping, interpretation and agricultural/environmental applications: a legacy for society, AP.TEM

Abstract

Mineralogy, particularly iron oxides, is directly linked to soil quality, which in turn is essential for addressing globally significant issues such as climate change mitigation, environmental preservation, and food security. However, there is a lack of such data for Brazilian soils, particularly spatial information covering large areas at a detailed scale. Literature provides evidence of the relationship between spectral data and the content of iron oxides in soil, as well as numerous studies predicting hematite and goethite. Thus, it is anticipated that legacy data, coupled with remote sensing and machine learning techniques, will enable the production of spatial distribution information for hematite and goethite across the national territory at a detailed scale. The objective of this undergraduate research scholarship is to generate detailed maps of hematite and goethite for the Brazilian territory, which will ultimately contribute to the final soil quality map. The necessary methodological steps include database organization, spectral processing (Kubelka-Munk function and Savitzky-Golay second derivative), determination of hematite and goethite content through bandwidth analysis, and spatialization using Random Forest (RF). The expected outcome is a detailed map of iron oxides in both surface and subsurface soils across Brazil. This information is unprecedented and of utmost importance for the construction of soil quality indicators and the soil quality map of Brazil.