A assessment of the silicate × phosphate interaction in tropical soils through adsorption models and spectroscopic tools.

• Grant number: 23/17893-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2024
• End date: February 28, 2025
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Leonardo Theodoro Bull
• Grantee: Isabella Arantes Giomo
• Host Institution: Faculdade de Ciências Agronômicas (FCA). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Phosphorus is a limiting element for production in tropical conditions, mainly due to the chemical bonding of this element's inner sphere to iron and aluminum sesquioxides. The application of silicate in tropical soils can increase the availability of phosphorus for crops. However, the phosphorus desorption processes from silicate application in soil are still poorly understood. The objective of this work is to assess phosphorus dynamics in Oxisols under silicate application using Langmuir and Freundlich adsorption isotherms. Additionally, it aims to characterize mineral surfaces after silicon application using spectroscopic techniques: Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Soils from six municipalities in the State of São Paulo will be selected and previously characterized physicochemically. The following parameters will be determined: i) maximum P and Si adsorption capacity; ii) residual P and Si; iii) Si adsorption kinetics; iv) specific surface area; v) mid-infrared spectroscopy (FTIR); and vi) X-ray photoelectron spectroscopy. The data will be fitted to the mathematical models proposed by Langmuir and Freundlich. Pearson correlation will also be used to determine the influence of physicochemical properties on residual P and Si levels in the soil.