Possibility of achieving organic yields for medicinal and aromatic plants by biofertilization with Azotobacter chroococcum

The aim of this study was to examine the effects of management practices and biofertilization on microbial activity in rhizosphere and yield of medicinal and aromatic plants. Field experiment was performed using four plant species: peppermint (Mentha × piperita L.), pot marigold (Calendula officinalis L.), sweet basil (Ocimum basilicum L.), and dill (Anethum graveolens L.). Treatments were arranged in a split-plot layout in four replicates using basic plots under conventional and organic management, and subplots with and without biofertilizer (Azotobacter chroococcum). Organic management positively affected the microbial number and activity. Biofertilization increased the total microbial number (13–21%), number of ammonifiers (13–60%), nitrogen-fixing bacteria (7–36%), actinomycetes (36–50%), fungi (60–100%), cellulolytic microorganisms (57–217%), dehydrogenase (28–52%) and ß-glucosidase activity (15–39%). The effects of management practices and biofertilization were highly significant for the yield of examined plants. The yields were higher on inoculated treatments both in conventional (5–26%) and organic (7–15%) growing system.