When applied correctly, the use of the biodynamic preparations has been shown to improve nutrient density of crops, storage life, pest and disease resistance, and even flavor. But, as Rudolf Steiner himself emphasized, biodynamics is something to add to common sense farming, not something that replaces everything altogether. You must continue to balance your soil pH even if it's just wood ash (Steiner remarks that potassium salts and calcium are not provided for in the balance we need them by nature) and you must supply some form of compost, ideally from materials made on your farm, especially from well-composted ruminant manures.
In Ed Yong's book, I Contain Multitudes: The Microbes Within Us and a Grander View of Life, he describes how human beings (and rats) can live with a sterile gut -- we aren't particularly healthy that way, but we can scrape by. But in the case of ruminants, they die within a few weeks if their guts are sterile. Why? Because cows don't primarily live off the food they eat but rather off the byproducts of fermentation in their gut. Cows culture microbes that produce a superabundance of vitamins as their excrement! This is part of why cow urine is treated like a multivitamin in India - it is absolutely loaded with nutrients.
In biodynamics, we base our fertility on the inner working of the cow. We want our soil to behave like a cow who can take poor grass, ferment it, and produce a superabundance of vitamins for the surrounding life. That is precisely what we want in our soil, so we always begin with 500 horn manure.
Never losing sight of common sense farming, biodynamics is an addition, not a subtraction, to what you're already doing right.
