A little. Research shows increased soil carbon under biodynamic using compost inputs compared to broad acre cultivation where little plant material returned to soil (no surprises here). Others also have analysed potions etc.
This is due to disolving of soluble plant compounds…compared to those same compounds being held in a dry biomass matrix. In some respects is is like a quick action soluble fertiliser (‘plant tea’) compared to a slow release fertiliser (spread biomass or mulch).
At the end of the day, the plants either dry or teas will move more of less the same concentration of nutrients (albeit low)…nitrogen may differ depending on how the plant matter is stored and what it has been exposed to (but biomass N is mostly very low in any event. Legumes are often thought to be higher as they produce some of their own through nitrogen fixing bacteria/nodules on the roots). One can’t use alchemy to create something from nothing.
The concentrations used are next to nothing and usually soil flora (bacteria, fungi, algae) are different to those found in compost. One lives in organic mater (with a benefit of breaking organic matter, some pathogenic etc) while the other lives in mainly a mineral matrix containing come organic matter (some are pathogenic, some benefit soil structure while others increase availability of soil nutrients etc). I am a bit sceptical that one flora can live and thrive in another substrate successfully. Soils are also alive with most soils used in agriculture having a popuution of microbes in one cm3 simikar to the human population of the world. Different soils have different soil flora due to a wide range of factors. Some also have higher pathogenic communities.
It is also worth noting that soils high in organic matter can assist in the control of pathogenic nematodes. Fungi that lives on these nematodes flourish in organic matter. Such effect is from organic matter and not from the spraying of potions.
If the potions were as wonderful as claimed, then one would not need to disseminate small concentrations of these potions to have an effect. The same effect could be achieved by spreading compost around a farm and is likely to have a greater effect.
The perceived benefit may be more associated with ritual beliefs rather than science. If one believes in the rituals, then one is more likely to believe in the benefits.
Edit: Should have also said that if one practices biodynamic farming and can sell their products at a premium in the market, to those who wish to pay a premium for such products, good luck to them as it makes good business sense to differentiate a product from others in the market place and also receive a premium price for efforts employed.