Utilization of microbial inoculation and compost for revitalization of soils

Improving the quality of reclaimed soils requires an active population of microorganisms which can promote plant growth. Increasing the activity of microorganisms can be done by adding nutrients, making agrotechnical soil improvements and by the inoculation of beneficial microorganisms. We investigated the role of fertilizer treatments on plant growth and nitrogen fixation in a pot experiment conducted under greenhouse conditions. The influence of the fertilizer type on numbers of bacteria was also investigated. The seeds were inoculated with the mixture of Azotobacter spp. and Rhizobium spp. The pot experiment was set up with the substrate from the mine spoil (North Bohemia coal basin, the Czech Republic) using Medicago sativa as test plants. The following treatments were used: compost 0, 20, 40, 120, 400, 800 t/ha and mineral fertilizer - ammonium sulphate. The doses of ammonium sulphate were calculated to be equivalent (in nitrogen content) to those of compost. Control variants without bacteria inoculation and fertilizers were also included. Inoculation with the mixture of Azotobacter-Rhizobium spp. significantly increased plant growth and nitrogenase activity. The nitrogenase activity was inhibited by mineral fertilizers in all doses used. The results of the study proved that compost application stimulated the growth of Azotobacter spp. and Rhizobium spp.