Chemical and Spectroscopic Characteristics of Humic Acids Under No-Tillage and Forest Systems
Creators: name: Rosset, Jean Sérgio
name: Tavares, Orlando Carlos Huertas
name: Pereira, Marcos Gervasio
name: do Carmo Lana, Maria
name: Schiavo, Jolimar Antonio
name: Ozório, Jefferson Matheus Barros
name: da Silva, Maryleide Ventura
name: da Cunha Andrade, Luis Humberto
name: Lima, Sandro Marcio
Publisher: name: Taylor & Francis
Year: 2023
Subjects: subject: Space Science
subject: Microbiology
subject: FOS: Biological sciences
subject: Environmental Sciences not elsewhere classified
subject: Chemical Sciences not elsewhere classified
subject: Ecology
subject: Biological Sciences not elsewhere classified
subject: Science Policy

description: This study aims to evaluate the no-tillage system (NT) with different implantation times and vegetation cover on changes in the chemical and structural compositions of soil humified organic matter. Five areas with different NT management histories were studied; for 6 (NT<sub>6</sub>), 14 (NT<sub>14</sub>), 22 (NT<sub>22</sub>) years with succession of soybean/corn crops; for 12 years and 4 more years with corn and <i>Brachiaria</i> (NT+B), pasture for 39 years and native forest. Soil samples were collected at the depths of 0.0–0.05 and 0.05–0.10 m. The changes in the quality of humic acid (HA) were evaluated by several chemical techniques (total organic carbon (TOC), fulvic acid fraction (FA), humic acid fraction (HA) and humin fraction (HU), ionizable functional groups, elemental composition) and spectroscopic techniques (UV–Vis absorption, fluorescence, and Fourier transform mid-infrared photoacoustic spectroscopy, called FTIR-PAS). On the surface, the TOC, carbon of the HA and HU fractions, total acidity, phenolic acidity, Carbon, Nitrogen, Sulfur, Hydrogen and Hydrogen/Carbon ratio were higher in the areas of forest, pasture and NT<sub>22</sub>. On the subsurface, the responses are the same as on the surface. However, the NT<sub>22</sub> system presents higher FA, HA, carboxylic acidity and humification degree (HD). UV–Vis absorption spectroscopy, fluorescence spectroscopy and FTIR-PAS can discriminate soils under different managements and under natural conditions. Agronomic practices have strongly affected the soil organic matter, in which the NT promotes the formation of HA with characteristics closer to those of the forest, as the implantation time increases, such as 22-year-old NT and pasture. This indicates that care must be taken in managing the no-till system to maximize its potential to promote stabilization of organic matter, thereby contributing to carbon sequestration. The humic substances contribute as sustainability indicators in agriculturalsystemsWere evaluated no-tillage system (NT) with different implantation times.The UV–Vis, fluorescence and FTIR-PAS discriminate soils under different managements.NT promotes humic acid formation with characteristics closer to those of the forest. The humic substances contribute as sustainability indicators in agriculturalsystems Were evaluated no-tillage system (NT) with different implantation times. The UV–Vis, fluorescence and FTIR-PAS discriminate soils under different managements. NT promotes humic acid formation with characteristics closer to those of the forest.