Microbial proliferation activity of biodynamic preparations and biodynamic compost

Biodynamic agriculture, different from other agroecological practices, comprises the use of humified preparations to stimulate humus formation in soil and increase plant growth and quality. The biodynamic preparations (BP), undergone a natural biotechnological transformation, were characterized by their C and N elemental content and carbon molecular distribution, and evaluated in vitro, for the first time, for their capability to proliferate some selected microbial strains active in the composting and humification processes of biomasses. Horn-manure preparation 500 showed no microbial bioactivity, meant as the capacity to induce microbial proliferation, thus confirming its role in direct abiotic stimulation of plant physiology. Preparation 500 K stemming from the 500 product after the combined addition of the six humified inflorescences preparations 502–507 revealed a microbial proliferation activity generally larger than each 502–507 preparation. Though the antioxidant activity of the tested BP generally followed their total phenolic content, the correlation was not confirmed by solid-state NMR spectra of the single BP, which rather suggested a role of oxygen- and carboxyl-containing groups. Different biodynamic composts obtained upon treatment of composting biomasses with the 502–507 preparations enabled a significant microbial growth to an ever-increasing extent with progressive compost maturation. The dissolved organic matter extracts from the corresponding biodynamic composts showed an even larger capacity to induce microbial growth, overcoming the bioactivity observed for humic extracts and compost tea obtained from non-biodynamic compost. This study has shown that the humified inflorescences used as 502–507 biodynamic preparations largely increase the microbial proliferation power when added to both biodynamic horn-manure (500 K) and composting biomasses. Our findings provide a solid scientific basis for the application of biodynamic practices aimed at improving soil health and crop quality.