Bioactivity of humic acids isolated from vermicomposts at different maturation stages
Background and aims
Vermicomposts are useful to improve environmental quality and sustainable agriculture. Moreover, it is enriched with highly bioactive humic acids (HAs)-like substances and can substitute no-renew source of humic substances to use as plant growth promoters in agriculture. The aim of this work was to evaluate the biological effects of HAs isolated at increasing vermicompost maturation stages.
Lateral root emergence, aqueous growth medium acidification and proton pumps of maize seedlings were used to monitor HAs bioactivity. Molecular conformation of the HAs was determined by size-exclusion and reverse-phase high performance liquid chromatography. We applied spectroscopy 13C-NMR on VC samples to follow the humification process.
We observed a decrease of carbohydrate content and selective preservation of hydrophobic alkyl and aryl C components by 13C-NMR during vermicompost maturation. Apparent molecular weight distribution of HAs did not change with vermicompost maturation, but was possible observed increase on hydrophobic moieties.
After 60 days of vermicomposting, all HAs promotes lateral root emergence, acidification of growth aqueous medium and induction of proton pumps without changes on apparent molecular weight but with enhance on hydrophobic domains.
KeywordsHumic substances Physiological effects Structural bioactivity ratio
The authors thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), International Foundation of Science(IFS) and National Institute of Science and Technology (INCT) for biological nitrogen fixation, for their financial support.
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