Effect of Vermicompost Enrichment with Chemical Fertilizer and Bacterial Treatments on Humification and Acid Humic Properties

Present study, aimed to evaluate the effects of vermicompost enrichment with bacterial (Pseudomonas and Azotobacter) and fertilizer (nitrogen, phosphorus and sulfur) treatments on humification indices and physico-chemical analyze of extracted humic acid, was conducted based on completely randomized design. Treatments were kept on incubator at 28°C for 60-days and finally analyzed for humic acid, elemental analysis, determination of functional groups and spectroscopic measuring of humic acid. Results showed that humification indices increased in all treatments during enrichment. VC+NSP and VCC treatments had the greatest and lowest indices, respectively. Elemental analysis of humic acid indicated that enrichment type has great effect on elemental composition of humic acid and added elements significantly increased humic acid functional groups. Also, according to measured infra-red spectrum, most of functional groups at all treatments were the same. Spectrophotometric ratios showed that highest amount of E3/E5 and E4/E6 ratios observed in VC+N and VC+NSP, respectively and the lowest ones was related to VC+Ps. Having regard to effect of organic matter stability in soil, it is expected that bacterial treatments and also VC+NSP would have more ability and efficiency in improving soil physico-chemical properties of soils.