PHOSPHATE × SILICATE INTERACTION: ADSORPTION KINETICS IN OXISOLS AND AGRONOMIC EFFICIENCY OF PHOSPHATE FERTILIZERS

• Grant number: 23/10749-0
• Support Opportunities: Regular Research Grants
• Duration: March 01, 2024 - February 28, 2026
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Leonardo Theodoro Bull
• Grantee: Leonardo Theodoro Bull
• Host Institution: Faculdade de Ciências Agronômicas (FCA). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil
• Associated researchers: Gustavo Rocha de Castro ; João Arthur Antonangelo

Abstract

Silicate application can enhance phosphorus (P) availability by competing for the same adsorption sites and increasing soil pH. However, the chemical and molecular mechanisms governing the competitive adsorption kinetics between silicon (Si) and phosphorus in Oxisols are still poorly understood. This study aims to evaluate the dynamic behavior of phosphorus in silicate-corrected Oxisols using spectroscopic techniques such X-ray absorption spectroscopy, chemical fractionation, and the agronomic efficiency of phosphate fertilizers will be assessed. Thus, 18 soil classes from the state of São Paulo will be included in the study. The following variable will be analyzed: i) The adsorption kinetics of Si; ii) remaining Si and SiMAC; iii) The remaining P and PMAC; iv) competitive adsorption between P and Si adjusting by the Langmuir isotherm; v) specific surface area (SSA) by BET method; vii) electron spectroscopy for chemical analysis,; viii) the Fourier-transform infrared spectroscopy; ix) diffusion of three phosphate sources (triple superphosphate, thermophosphate, and phosphate rock); x) agronomic efficiency of P using Urochloa ruziziensis plants; and xi) chemical fractionation and spectroscopy will be performed on the soils used in this study. The collected data will undergo tests for normality and homogeneity, followed by analysis of variance and mean comparison tests, respectively. Mathematical models will also be employed to determine the soil's phosphorus retention capacity factors and diffusion time. (AU)