Mapping technology: spatial variability of total phosphorus and soil adsorption by indirect techniques

• Grant number: 19/06195-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Effective date (Start): June 01, 2019
• Effective date (End): July 31, 2021
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: José Marques Júnior
• Grantee: Luiz Gustavo Rosa Campos
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

The study aims to evaluate the potential of X-ray Fluorescence (EFRX), Diffuse Reflectance Spectroscopy (ERD) and Magnetic Susceptibility (SM) in estimating the spatial variability of total phosphorus and adsorbed in soils with wide mineralogical variation. The study will be carried out in the field of Teaching, Research and Production Finance of the Faculty of Agrarian and Veterinary Sciences - UNESP. Soils are products of the weathering of basalt / sandstone rocks. A total of 100 samples of soils in the 0 - 0.2 m layer, representing the lithologies and landscape forms, will be collected. Samples will be submitted to mineralogical analysis by X-ray diffraction for the characterization of hematite (Hm), goethite (Gt), gibbsite (Gb) and kaolinite (Ct) of soil clay fraction. The estimated total phosphorus will be measured by X-ray Fluorescence Spectroscopy and phosphorus adsorbed by chemical methods and estimated by diffuse reflectance spectroscopy and magnetic susceptibility. The results will be submitted to descriptive statistical analysis, partial regression of least squares (PLSR) and geostatistics. The geostatistical technique will allow to describe the spatial distribution of P as covariate factor of the lithological and mineralogical variation of the study area. Then, the maps of P obtained by each technique will be confronted to obtain the error map, that is, to evaluate how much a technique underestimates or overestimates the content and the spatial variability of P. In turn, the spatial dependence of the P soil minerals will be evaluated by cross-semivariograms. It expects to represent the spatial variation of the total phosphor and adsorbed by simpler, cheaper, non-destructive techniques and fast results delivery. Assist decision making and more assertive management of phosphate applications, minimizing cost and negative impacts to the environment.