Horn Manure and Horn Silica: What Each Spray Does

Horn manure, preparation 500, is cow manure packed into a cow horn, buried in the ground over winter, then stirred in water for an hour and sprayed on bare soil in the evening. Horn silica, preparation 501, is ground quartz packed into a cow horn, buried over summer, then stirred the same way and sprayed on the leaves near sunrise. The two are a pair worked in opposite seasons, opposite burial depths of the calendar, and opposite ends of the plant: one addresses the soil, the other the leaf.

What is horn manure made of, and how is it buried?

Horn manure is made from fresh cow manure, packed into the horns of a cow and buried in the ground for the whole winter. The underground period is where the transformation happens: by the time the horns are dug up, the manure has become, in the words of the practice, moist, colloidal, dark brown to black, and largely odourless, with at most a faint earthy smell. A batch that still smells strongly of manure, or has dried out, has not transformed and is set aside.

What is horn silica made of, and how is it buried?

Horn silica is made from finely ground quartz, usually mixed into a paste with rainwater, packed into cow horns and buried for the summer months rather than the winter, typically from spring to early autumn. Where horn manure spends the dark, cold half of the year underground, horn silica spends the light, warm half. The two preparations are made, deliberately, on opposite calendars.

How much is used, and how is each one prepared for spraying?

Both preparations are used in tiny amounts and both are stirred by hand before spraying. Horn manure is applied at roughly 100 grams of material per hectare, mixed into rainwater that has been warmed to roughly body temperature. Horn silica is applied at a far smaller rate, around 4 grams per hectare in 30 to 35 litres of water. In both cases, the mixture is stirred vigorously for a full hour, a method known in the practice as dynamising, before it is sprayed within one to three hours of finishing the stir.

When and how is each one sprayed?

Horn manure is sprayed onto the soil itself, not onto the plants, and the timing is specific: in the evening, not before five in the afternoon in summer or four in winter, with calm, overcast conditions preferred over wind, strong sun, rain or frost. It is applied at least twice a year, generally in spring and in autumn, when the soil is warm and damp enough for biological activity to be starting or still active.

Horn silica is sprayed the opposite way around on every count that matters. It goes onto the leaves, not the soil, and the timing favours the morning: before eight o'clock, as close to sunrise as practical, on a sunny morning with little wind and a temperature that does not climb much above 22 degrees Celsius. It is used most in spring and autumn as well, and especially after a stretch of rain or persistent damp, when the practice holds that plants benefit from a drying, light-focused counterbalance.

Why are the two preparations treated as opposites?

The practice describes horn manure and horn silica as working in polarity: one builds structure and biological life in the soil, feeding root growth and the dissolving of minerals the plant can use; the other works on the aerial parts of the plant, associated in the practice with ripening, a firmer growth habit and resistance to disease. Whether or not a grower accepts every claim made for either spray, the working logic is consistent and worth stating plainly: a preparation buried in winter and sprayed on soil in the evening, paired with a preparation buried in summer and sprayed on leaves near dawn, is built around the same opposition the rest of biodynamic method returns to again and again, between what happens underground and what happens in light.

How do these two sprays relate to the six compost preparations?

Horn manure and horn silica are field sprays, used directly on soil or leaf in small, diluted doses. The six compost preparations, made from yarrow, chamomile, stinging nettle, oak bark, dandelion and valerian, are a different category entirely: they are inserted into a finished compost heap to guide how it matures, not sprayed onto a field. A holding that keeps both practices going is running two separate routines on two separate calendars, one for the heap and one for the open ground, and neither substitutes for the other.

What does a grower actually need to get started?

Two cow horns per preparation at minimum, a supply of fresh manure for one and finely ground quartz for the other, a patch of ground to bury them in for a season, a container and a stirring implement for the hour of dynamising, and a watering can or a backpack sprayer fine enough to distribute a few grams of material evenly over a hectare. The scarcest resource is usually the horns themselves and the burial site, which has to be left undisturbed for months at a time. Many growers who are not ready to make their own buy finished preparations from an established supplier rather than skip the practice for a season, since a badly transformed batch is wasted ground and wasted time either way.

The two sprays are small in volume and large in the attention they demand: a precise season to bury them, a precise hour to stir them, and a precise window of weather to apply them. That precision, more than the ingredients themselves, is what the practice asks a grower to keep.