Understanding phonolite solubility through bioweathering agents

• Grant number: 24/18851-1
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: March 26, 2025
• End date: April 09, 2025
• Field of knowledge: Agronomical Sciences - Agronomy
• Principal Investigator: Carlos Alexandre Costa Crusciol
• Grantee: Sirlene Lopes de Oliveira
• Supervisor: Steeve Bonneville
• Host Institution: Faculdade de Ciências Agronômicas (FCA). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil
• Institution abroad: Université Libre de Bruxelles (ULB), Belgium
• Associated to the scholarship: 22/15278-3 - Long-term impacts of phonolite application as an alternative source of potassium in soybean-maize succession, BP.DR

Abstract

One of the primary challenges in using ground rocks as a nutrient source for plants is their relatively low solubility, which can limit crop yields. To address this issue, researchers have explored biological methods to enhance the solubilization of these minerals. In natural systems, plants, bacteria, and fungi play crucial roles in bioweathering, primarily through the secretion of low molecular weight organic acids. These acids weaken mineral bonds and facilitate the release of nutrients into the soil solution. Additionally, dissolved organic matter (DOM) may contribute to the solubilization of silicate minerals. To date, however, there have been no studies examining the role and efficacy of organic acids and dissolved organic matter in the dissolution of hydrothermalized phonolite, a potassium (K)-rich rock. This proposal aims to investigate the potential of organic acids and dissolved organic matter in solubilizing K-feldspar (hydrothermalized phonolite) under controlled conditions. Two experiments will be conducted at the Faculty of Sciences of the Université Libre de Bruxelles. The first experiment will assess the solubility of potassium from phonolite using various organic acid solutions (oxalic, malic, and citric) across four pH ranges: 4, 5, 6, and 7, along with a control (3x4+1). Aliquots of the solution will be collected regularly until the 50th day after the experiment's initiation, during which potassium content will be measured. Dissolution will be analyzed using a kinetic model. The second experiment will evaluate the impact of DOM, extracted from a commercial organic compound, on the weathering of hydrothermalized phonolite and the subsequent solubility of potassium. Four DOM solutions will be tested, with pH levels adjusted to 3, 4, 5, and 6. Additionally, four pH ranges of oxalic acid will be tested (pH: 3, 4, 5, and 6), resulting in a total of 4 DOM solutions, 4 oxalic acid solutions, plus a control (4 x 4 + 1). Effluents will be collected regularly and analyzed for silicon (Si), aluminum (Al), and potassium (K) content. The chemical and physical characterizations of both experiments will be conducted using X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS). The data will undergo tests for homogeneity and homoscedasticity, and when prerequisites are satisfied, will be subjected to analysis of variance (ANOVA) and Tukey's test (p<0.05).Keywords: biological weathering, dissolution, K-feldspar, Microscopy techniques