Article,
Humic extracts of hydrochar and Amazonian Dark Earth: Molecular characteristics and effects on maize seed germination
SCIENCE OF THE TOTAL ENVIRONMENT, (2020)
DOI: 10.1016/j.scitotenv.2019.135000
Abstract
Inspired by the presence of anthropogenic organic matter in highly
fertile Amazonian Dark Earth (ADE), which is attributed to the
transformation of organic matter over thousands of years, we explored
hydrothermal carbonization as an alternative for humic-like substances
(HLS) production. Hydrothermal carbonization of sugarcane industry
byproducts (bagasse and vinasse) in the presence and absence of H3PO4
afforded HLS, which were isolated and compared with humic substances
(HS) isolated from ADE in terms of molecular composition and maize seed
germination activity. HLS isolated from sugarcane bagasse hydrochar
produced in the presence or absence of H3PO4 comprised both hydrophobic
and hydrophilic moieties, differing from other HLS mainly in terms of
phenolic content, while HLS isolated from vinasse hydrochar featured
hydrophobic structures mainly comprising aliphatic moieties. Compared to
that of HLS, the structure of soil-derived HS reflected an increased
contribution of fresh organic matter input and, hence, featured a higher
content of O-alkyl moieties. HLS derived from lignocellulosic biomass
were rich in phenolics and promoted maize seed germination more
effectively than HLS comprising alkyl moieties. Thus, HLS isolated from
bagasse hydrochar had the highest bioactivity, as the presence of
amphiphilic moieties therein seemed to facilitate the release of
bioactive molecules from supramolecular structures and stimulate seed
germination. Based on the above results, the hydrothermal carbonization
of lignocellulosic biomass was concluded to be a viable method of
producing amphiphilic HLS for use as plant growth promoters. (C) 2019
Elsevier B.V. All rights reserved.
