Comparison of structural diversity of humic acid types extracted from conventional organic sources in agriculture

Humic acid is an organic compound that can improve the physical, chemical and biological properties of soil. In addition, it plays an important role in increasing plant growth and yield. This composition can be extracted from various sources that are rich in organic materials such as composts, coal, humus materials and soil. In order to know the spectral and structural characteristics of this compound, humic acid was extracted from different organic sources in 2021. The amounts of carbon, oxygen, hydrogen and nitrogen elements in the extracted humic acids were determined by elemental analyzer, functional groups by FTIR and the spectrophotometric absorption ratios of E3/E5 and E4/E6 were determined by spectrophotometer in Department of Soil Science and Engineering laboratory, Razi University, Kermanshah. The lowest H/C ratio in the extracted humic acids was observed from municipal waste compost (1.05) and vermicompost (1.09), the highest O/C ratio was in humic acid extracted from municipal waste compost (0.70) and vermicompost (0.59), and the lowest C/N ratio was in humic acid of chicken manure (11.84). According to the results of FTIR analysis, the strongest absorption bands were observed at 3400 cm-1, 2900-3000 cm-1, 1600- 1700 cm-1 and 1000-1100 cm-1. The highest ratio of E3/E5 was found in humic acid extracted from chicken manure (12.81) and sheep manure (10.61) and the lowest amount was observed in municipal waste compost (2.00). The highest ratio of E4/E6 was obtained in humic acid extracted from chicken manure (7.31) and the lowest amount of E4/E6 was observed in humic acid obtained from municipal waste compost (4.70).