The other three biodynamic preparations are used as sprays.
Steiner felt cow manure was immensely fertile: cows can eat from just one meadow but her digested grass or manure could keep two meadows fertile. He said her manure was so special because the digestive energy the cow released when eating her grass was not lost but stayed in her stomach because the horns on her head stopped this energy leaving her body. This is why biodynamics is the only farming system which prohibits the de-horning of cows. When you walk into a cow field the cows lower their head and point their horns at you. It’s their way of “sensing” you.
The cow horns’ sensitivity is why Steiner used them as sheaths for the first two of his spray preparations: horn manure and horn silica. In each case the horns are filled either with cow manure or ground-up silica, an abundant mineral (also called quartz) and buried for six months: over autumn (dark) for the horn manure and over summer (light) for the horn silica.
Once dug up the horns are removed and their contents diluted in water and sprayed: horn manure on the soil to enliven the earth and its terroir-giving character, and horn silica over the vines to enliven heat and light forces to give the wine more fruit character and a greater capacity to age. The idea with the two preparations is the vines must work hard: stretching their roots down into the earth (terroir), and stretching their shoots up to sun (taste).
The third spray preparation is made from the medicinal common horsetail (Equisetum arvense) plant. This is sprayed on either on the crops (as a fresh tea) or on the soil (as a macerated tea). Common horsetail lives in damp, dark places (shady riverbanks) but does not suffer rot or mildew, fungal diseases to which grapevines are very susceptible. Spraying common horsetail gives the vineyard the capacity to keep fungus diseases in their place: in the soil, but not to jump up on to the vines.