Biodynamic farming revisited: Deciphering the microbiome of biodynamic preparations and associated spray-extracts, with insights into potential effects on apple rhizosphere microbiome

The roles of compost in agricultural systems, especially in improving the soil ecosystem functions have extensively been explored. However, not much is known about the microbiome of biodynamic manures, and plant-based biodynamic preparations used in biodynamic agriculture. In addition, the potential benefits of incorporating sprays from such preparations into organic and integrated farming systems are rather unexplored. In this study, we used amplicon sequencing and qPCR techniques to profile the microbiome of non-biodynamic composts, biodynamic-manures, and plant preparations from Austria and France, and the likely effects of extracts from these products on the rhizosphere of apple managed under contrasting management systems. The microbiome of biodynamic manures differed from that of plant-based biodynamic preparations, as well as non-biodynamic composts; in addition, differences between biodynamic manures were evidenced between countries of production. Beneficial bacteria genera under families Rhizobiaceae, Pseudomonadaceae, Nitrosomonadaceae, Flavobacteriaceae, Devosiaceae, Clostridiaceae, Burkholderiaceae, Paenibacillaceae, and Bacillaceae were seen in biodynamic manures, including their respective extracts. The effect of treatment was higher at one-month post-inoculation but was reduced after three months in organic and integrated fields. Moreover, beneficial fungal genus like Beauveria was highly abundant in organic field, while Penicillium was enriched in the integrated field, especially at second sampling. For both fields and sampling time, a higher bacterial diversity in comparison to control was observed post-inoculation in comparison to control, suggesting that consistent use of sprays from composts or biodynamic manures could induce shift in soil microbiome in the different farming systems. Our findings provide a basis for adopting biodynamic formulations (sprays and manures) in different farming practices to maintain or restore vitality of agricultural soils.