Structural modification of phyllosilicates aiming at the solubilization of interlayer potassium for plant uptake

• Grant number: 25/15571-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: October 01, 2025
• End date: September 30, 2026
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Antonio Carlos de Azevedo
• Grantee: Luana Teixeira Correia
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated research grant: 24/16600-1 - Changing a sandy soil with K-clays from mining waste to endure the climate change, AP.R
• Associated scholarship(s): 25/26388-2 - Structural and surface characterization of aluminum-pillared clays aiming at reducing potassium fixation, BE.EP.IC

Abstract

Brazil is highly dependent on external sources of potassium fertilizers, importingapproximately 95% of the raw material it needs. Even with the start of operations of theAutazes Potassium Project, located in the state of Amazonas, this dependence will notbe completely met. In this context, the need to develop and make viable alternative anddomestic sources of potassium stands out. One such alternative is the availability ofpotassium retained in the interlayers of 2:1 phyllosilicates. The availability of thispotassium, however, is controlled by the negative charge of the layers of the claystructure, which makes its extraction difficult. Furthermore, even when K¿ is releasedfrom the siloxane cavity of these minerals, it can be quickly recaptured if there is anincrease in its ionic activity in the soil solution (potassium fixation). In parallel, duringpedogenesis, 2:1 phyllosilicates can give rise to 2:1 hydroxy-interlayer minerals (2:1HE), which contain hydroxy-aluminum polymers that act both to partially block accessto the interlayers and to partially neutralize the charge in the layer. Bearing in mindthese two challenges, the removal of K¿ from the interlayers and the subsequentblocking of high-charge positions by hydroxy-Al polymers, we aimed to test methodsfor (i) extraction of potassium from the interlayers of K-clays, followed by (ii) structuralstabilization of this potassium. This project has the potential to contribute to theadvancement of agriculture in Brazil by increasing the bioavailability of soil potassium.