Visible and near infrared spectra of Ferralsols according to their structural features.

• Autor(a) principal: OLIVEIRA, J. F. de
• Data de Publicação: 2016
• Outros Autores: BROSSARD, M., CORAZZA, E. J., MARCHAO, R. L., GUIMARÃES, M. de F.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da EMBRAPA (Repository Open Access to Scientific Information from EMBRAPA - Alice)
• Texto Completo: http://www.alice.cnptia.embrapa.br/alice/handle/doc/1059216; https://doi.org/10.1255/jnirs.1202
• topic: Espectroscopia de refletância difusa; Microped; Solo mineral; Diffuse reflectance spectroscopy; Latosol; Soil mineral; Estrutura do Solo; Latossolo; Soil structure

ABSTRACT: In soil science, structural features of soils are an important attribute; soils can be characterised by proportional size distribution of aggregates and the pore space between and within those aggregates. The objective of this study was to evaluate the relationship between the visible and near infrared (Vis?NIR) spectra and microaggregates from a collection of Ferralsols. Our dataset consists of 56 spectra from seven soil profiles of kaolinitic and oxidic-gibbsitic Ferralsols. Soils were characterised according to their morphological features: those with a typical porous massive structure and those with a cohesive massive structure. Size distribution of five classes of microaggregate was determined (1000?2000 µm, 500?1000 µm, 250?500 µm, 105?250 µm and < 105?µm). From the soil spectra, we determined the CIE (Commission Internationale de l'Éclairage) red index (RICIE) and the absorption intensities of kaolinite (IKa) and gibbsite (IGb). The predominant fraction of microaggregates exhibited sizes between 250 and 1000µm (&#934;250?1000). The proportional increase of this microaggregate class in the soils increased the scattering and variability of reflected light, particularly when soil samples showed more than 0.50 g g?1 of &#934;250?1000. The microaggregate size explained over 55% of reflectance intensity variability of wavelengths in the vis?NIR regions, principally on reflectance intensity and concavity of the spectra at 436 nm, 546 nm and 2236 nm, which decreases with increased proportion of &#934;250?1000. Thus, different structural features of Ferralsols can be directly evaluated through Vis?NIR spectroscopy, even in samples sieved through 2.00 mm. These results highlight the potential use of Vis?NIR spectroscopy in studies of soil classification, soil physical behaviour and soil physical fertility and environmental studies, principally by a new method of analysing bulk density and structure of soil directly from the soil spectra, without the need for predictive models. As well as spectra, RICIE,IKa and IGb can be used to characterise the different structural features of Ferralsols.