Quantificação do teor de matéria orgânica de diferentes tipos de solos por infravermelho próximo (NIR)

Abstract

Soil Organic Matter (SOM) plays a vital role from chemical, physical, and biological perspectives. Its origin, chemical composition, transformations, and functions have been the focus of numerous studies across various branches of Soil Science. However, these studies require accurate knowledge of SOM content. Currently, the most commonly employed methodology for determining SOM content is based on its oxidation to CO₂ by dichromate ions in a strongly acidic medium. In the method originally proposed by Walkley and Black in 1934, the amount of reduced Cr(III) ions is determined by titrating the excess dichromate with Fe³⁺ ions. However, due to the high generation of toxic waste and the challenges associated with its disposal, alternative methods for SOM quantification have been explored. Among these, Near- Infrared Spectroscopy (NIR) stands out as a fast, non-destructive, easy-to-use, highly reproducible, and sustainable analytical technique that can be applied to SOM quantification. In this study, methodological aspects involving the use of a portable NIR spectrophotometer for determining SOM content were evaluated. The objective of this work was to assess the application of NIR for determining SOM content using 56 soil samples. Different preprocessing techniques were tested, including first and second derivatives, Multiplicative Scatter Correction (MSC), and Standard Normal Variate (SNV).