Peat humic substances and earthworm biohumus extracts for agricultural applications

Extracts for agricultural use were prepared using cavitation method at 45 °C and at 95 °C from peat and earthworm biohumus. Samples of all studied extracts had similar dry-matter content. Peat humic substances and earthworm biohumus extracts were analysed using UV-Vis, FT-IR, and fluorescence spectrometry. Trace element analysis was performed with atomic absorption spectrometry. Extracts were tested for acidity, conductivity, humic acid concentration, and carboxyl group concentration. Hydrophobicity was assessed using a water-polyethylene glycol two-phase system and calculation of the partition coefficient. Total nitrogen and phosphorus concentration was determined. Concentration of the humic substances slightly changed during the heating process. Significant changes in total phosphorus concentration was observed both in earthworm humus and peat extract. Thermal treatment caused decrease of hydrophobicity and lower concentration of organic matter in extracts, while carboxyl group concentrations in isolated humic substances practically did not change. The calculated ratio from UV-Vis spectra showed significant difference in humification degree of samples.