Microbial transformation of traditional fermented fertilizer bokashi alters chemical composition and improves plant growth

Bokashi is an organic soil amendment that makes use of microbial processes to break down agricultural waste and create a nutrient-rich fertilizer. The benefits of various types of bokashi on soil fertility and plant growth are well documented, however the changes in microbial community composition and nutrients during bokashi maturation remain poorly characterized. Here, we aimed to identify potential differences in the quality of bokashi made using different ingredients and to investigate the biochemical transformation and microbial community succession of bokashi throughout the maturation process. We compared the effects of these different types of bokashi on the growth of cucumber (Cucumis sativus) and kale (Brassica napus subsp. pabularia) seedlings, measured concentrations of NH4+ and PO43-, and characterized the bokashi bacterial and fungal communities over a 12-day maturation period. We found that cucumber and kale plants growing in all types of bokashi-amended soils exhibited increased chlorophyll levels and dry biomass. During bokashi maturation, we observed a decrease in available PO43-, and an increase in NH4+. There also appeared to be an increase in relative abundances of decomposers and beneficial microbes and a decrease in putative plant pathogens. Regardless of starting bokashi ingredients and differences in microbial composition and nutrient trends, all types of bokashi similarly improve plant growth and contain beneficial microbes.