What is Preparation 500 in biodynamics?

• A. Bone meal: powdered bone applied to the soil
• B. Compost tea enriched with seaweed
• C. Horn Manure: cow manure stored in a cow's horn, buried, then dynamised and sprayed onto the soil
• D. Copper sulfate spray for vines

Answer: (C)

Preparation 500 is the horn manure preparation used in biodynamics to energize and stimulate soil life. It involves packing cow manure into a cow horn, burying it in the soil over winter, then digging it up, drying or grinding the material, and dynamising it (succussion) before it is sprayed onto the soil. The idea is to boost microbial activity, humus formation, and overall soil vitality rather than to provide direct nutrient for the plant through foliar or root feeding.

The other options don’t fit because they describe materials or practices not identified as Preparation 500: bone meal is a conventional fertilizer, not a biodynamic horn preparation; compost tea with seaweed isn’t one of the biodynamic preparations; copper sulfate is a chemical fungicide, not a biodynamic spray preparation.