Evaluating the influence of soil mineralogy and organic matter quality on the structural degradation of oxisols under no-till using advanced and non-conventional techniques

• Grant number: 17/01522-1
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: April 01, 2017
• End date: January 15, 2018
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Paulo Leonel Libardi
• Grantee: Márcio Renato Nunes
• Supervisor: Harold Van Es
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Institution abroad: Cornell University, United States
• Associated to the scholarship: 15/12934-3 - Factors of structural degradation in clayey soils under "no-tillage", BP.DR

Abstract

Structural degradation on the subsurface layer of soils reduces the effectiveness of no-till (NT) as a sustainable soil practice in crop production systems. In the PhD project (process 2015/12934-3), we are studying key factors that may influence soil structural degradation in Oxisols under NT. Results obtained have shown that Oxisols under NT may exhibit structural degradation when compared to the natural non-cultivated Oxisols. The processes of clay dispersion and the consequent transport of such particles to the subsurface layer were observed, with possible blockage of soil pores and harmful consequences to the water transport and root development in this degraded environment. Results also showed that the lower structural stability of the cultivated vs. non-cultivated Oxisols is strongly correlated with soil organic carbon content and with chemical attributes that affects the soil physico-chemical proprieties. The soil mineralogy and quality of the soil organic matter may differently affect the physico-chemical properties of these soils and the above-mentioned soil degradation process. Thus, during the proposed internship abroad, we intend to study the relationships between soil organic matter (quality and quantity), soil clay mineralogical constituents and the structural stability of Oxisols, using advanced non-conventional techniques (e.g. X-ray microtomography, mercury intrusion porosimetry, laser induced fluorescence), in order to elucidate the influence of these parameters on the Oxisol structural degradation process. The study will consider three Oxisols of different regions, with samples collected at the surface and subsurface layers in NT crop systems compared to reference areas of non-cultivated Oxisols under native vegetation. For this study the following evaluations will be carried out: kaolinite and gibbsite contents of the clay fraction by thermo gravimetric analysis; amount and quality of the organic matter, by conventional and spectroscopic analysis; soil specific surface area by nitrogen adsorption analysis; pore size distribution by X-ray microtomography and mercury intrusion porosimetry. The study will contribute to a more detailed understanding of the process of soil structural degradation in tropical soils, considering different soil mineralogy and different soil organic matter inputs in Oxisols managed under NT.