Biodynamic Preparations — 500 (Horn Manure), 501 (Horn Silica), 508 (Horsetail)

Preparations 500, 501, and 508 are the three primary field spray preparations indicated by Rudolf Steiner in his 1924 Agriculture Course, delivered in eight lectures at Koberwitz, Silesia. They are applied as potentized liquid sprays directly to the soil or plant canopy and are considered to work in complementary polarity with one another. Preparation 500 (horn manure) works below ground, stimulating root development, humus formation, and soil microbial life. Preparation 501 (horn silica) works above ground, strengthening photosynthesis and supporting fruit ripening. Preparation 508, a tea made from the silica-rich plant Equisetum arvense (common field horsetail), is used to counteract excessive moisture and fungal disease pressure. Together they are the practical foundation of biodynamic vineyard management.

• 500 is sprayed directly onto moist soil, not onto foliage, preferably in the late afternoon
• 501 is applied as a fine mist onto foliage in the early morning, ideally before the sun reaches the plants, at approximately 4 grams per hectare
• 508 can be used as both a foliar spray (fresh tea) and a soil spray (fermented brew) to help balance fungal and bacterial organisms
• All three preparations are stirred vigorously for one hour before application to create the hydrodynamic vortex biodynamic practitioners call dynamization

The making of biodynamic preparations follows specific protocols tied to seasonal cycles. Preparation 500 is created by packing fresh cow manure into a bovine horn and burying it in soil during winter; after approximately six months underground, the transformed material takes on a colloidal, dark brown, humus-like quality with an earthy smell. Before use it is stirred vigorously for exactly one hour in clean, lukewarm water before being sprayed onto the soil. Preparation 501 uses quartz crystal ground to a fine flour-like consistency, packed into a horn and buried during the summer months; it is then stirred for one hour and sprayed as a fine mist at dawn onto the aerial parts of the plant. Preparation 508 is prepared by boiling dried Equisetum arvense herb in water to make a tea, or allowing it to ferment over ten to fourteen days to produce a more concentrated brew used as a soil drench.

• Winter burial (approximately October to March) for Prep 500 aligns with the soil's dormant, inward-drawing phase
• Summer burial (approximately May to August) for Prep 501 allows the ground quartz to receive peak light and warmth cycles
• Fresh Prep 508 tea is used as a foliar spray; fermented 508 brew is applied as a soil spray to encourage beneficial soil fungi
• Only clean water, preferably rainwater or spring water warmed to approximately body temperature, is used for stirring the field preparations

Biodynamic proponents argue that consistent use of Preparations 500 and 501 reshapes vineyard health by improving soil biology, nutrient cycling, and vine physiology. Preparation 500 is said to stimulate root development and humus formation, increasing the depth and complexity of the vine's interaction with the soil. Preparation 501 is associated with enhanced photosynthesis, improved flavor, and better ripening and storage quality in the fruit. Preparation 508 reduces fungal pressure, particularly powdery and downy mildew, without synthetic inputs. Scientific evidence is mixed: some peer-reviewed trials have found no measurable difference in soil quality or yield between biodynamic and organic vineyard management, while others document increased microbial diversity and vine physiological benefits. Critics note that observed improvements may derive from the holistic reduction of synthetic inputs and increased grower attention rather than the preparations themselves.

• Preparation 500 is reported to stimulate seed germination, vertical root growth, and microbial life in the rhizosphere
• Preparation 501 strengthens photosynthesis, regulates leaf growth, and is particularly useful during and after rainy periods
• Horsetail (508) is high in silica, which is believed to reduce the impact of excess moisture on plant tissues that leads to fungal colonization
• A five-year Swiss field trial (2016 to 2020) testing Preparations 500 and 501 against an organic control found the scientific picture remains complex, with evidence for and against specific biodynamic effects

Biodynamic viticulture is practiced across more than 20 countries, with the heaviest concentration in quality-focused European wine regions. Nicolas Joly at Château de la Roche aux Moines in Savennières is among the most cited pioneers: he began experimenting with biodynamics in 1980, converted the entire estate by 1984, and his 7-hectare Clos de la Coulée de Serrant monopole, first planted by Cistercian monks in 1130, is widely regarded as a benchmark for biodynamic Chenin Blanc. In Burgundy, the late Anne-Claude Leflaive of Domaine Leflaive credited biodynamic conversion with saving a badly diseased vineyard and producing some of the estate's most prized wines. Austria is particularly notable, with 1,431 hectares of biodynamically farmed vineyards recorded in 2025, and the country is regarded as a role model within Demeter International for its strict standards. In North America, producers in California, Oregon, and Washington have adopted Demeter certification, and biodynamic methods are practiced in Australia, New Zealand, Chile, Argentina, and South Africa.

• Nicolas Joly's Clos de la Coulée de Serrant in Savennières holds its own Appellation d'Origine Contrôlée and has been farmed biodynamically since 1981
• Demeter International operates across 63 member countries, with over 7,000 certified farmers worldwide as of 2025
• Austria recorded 1,431 hectares of biodynamically farmed vineyards in 2025, with Demeter Austria and the respekt-BIODYN association both active
• France led biodynamic viticulture with approximately 4,700 hectares and around 300 certified farms as of 2017 data, with Alsace, Burgundy, and the Loire Valley particularly prominent

The scientific evaluation of biodynamic preparations sits at an unusual intersection of verifiable agronomic outcomes and philosophically contested mechanisms. Certain aspects of biodynamic farming, such as the elimination of synthetic pesticides and fertilizers, the use of compost, and increased biodiversity, are well supported by mainstream agronomy and clearly contribute to soil health. Equisetum arvense (Prep 508) has attracted the most scientific attention: research presented at the 2018 International Conference on Biodynamic Research found anti-sporulation activity against mildew and documented it as an activator of plant defense mechanisms, and it became the first biodynamic preparation approved under EU phytopharmaceutical regulation (EC 1107/2009). However, the ultra-dilute application rates of Preparations 500 and 501, and the theoretical framework of cosmic and etheric forces, remain outside mainstream biochemistry. Long-term field studies have found that improved quality in biodynamically farmed vineyards cannot always be distinguished from well-managed organic farming, and causation between specific preparations and outcomes remains debated.

• Equisetum arvense decoction (508) is the first biodynamic preparation approved under EU general phytopharmaceutical regulation EC 1107/2009
• The high silica content of Equisetum arvense is thought to reduce the impact of excess moisture on plant tissues and activate plant defense mechanisms
• A long-term California study found no measurable difference between biodynamic and organic vineyard management for soil quality, yield per vine, or berry weight
• Most agronomists attribute the genuine quality gains observed in biodynamic vineyards to the holistic elimination of synthetics, careful compost use, and intensified grower attention rather than to the esoteric potentization mechanism

Central to biodynamic practice is the synchronization of preparation applications and vineyard work with lunar and planetary cycles, formalized in the biodynamic sowing and planting calendar. Maria Thun, who began empirical trials on her farm near Darmstadt in the 1950s, developed the modern calendar by observing the moon's passage through the twelve zodiac constellations and its correlations with plant growth. She divided the zodiac into four categories linked to the four classical elements and the corresponding parts of the plant: earth constellations correspond to root days, water to leaf days, air to flower days, and fire or light constellations to fruit days. In viticulture, fruit days are considered optimal for working in the vineyard and for tasting wine. Preparation 500 is conventionally applied in spring as soil awakens, while 501 is typically sprayed two to six times per season during periods of active growth. The biodynamic calendar, now published annually in over 27 languages, continues to be used by practitioners worldwide, though mainstream viticulturists view the cosmic timing as unproven and separate from the agronomic benefits of the underlying farming system.

• Maria Thun began her calendar research in the early 1950s; annual publication of The Maria Thun Biodynamic Sowing and Planting Calendar has continued for over sixty years
• The four day types (root, leaf, flower, fruit) correspond to the moon's transit through zodiac constellations associated with the four elements: earth, water, air, and fire
• Preparation 508 is typically applied prophylactically in the days before a full moon and during moist, changeable weather when fungal conditions are most likely
• The biodynamic calendar is now available in 27 languages and is used by growers across viticulture, market gardening, and arable farming worldwide