A lot has been reported on how to manage manure from beef and dairy cattle, but thanks to a slightly different digestive system and sometimes a different diet, handling horse manure has its own protocols. Addressing these in a recent webinar was Marcel Sachse, owner of Pinsch of Soil Farm in Langley, BC.
A horse farm as well as a vegetable operation, Sachse talked about how he managed manure while sitting on Jacobsen Creek and its watershed and utilizing it for the crops he grows. Pinsch of Soil Farm composts its horse manure (also fondly referred to as “road apples” and “horse hooey”) along with the horses’ bedding (comprised of wood shavings), soiled hay from stalls and garden trimmings and kitchen waste. The compost is eventually safely used on their vegetables.
For those concerned about any outside influence in the compost, Sachse noted that a portion of any medications his horses are given, once metabolized, are excreted in the manure and the urine, but said based on his conversations with veterinarians and composting professionals, it’s generally accepted that a good composting process – consistent high temperatures plus consistent decomposition – will likely reduce or eliminate most medications, including antibiotics.
“You need to compost for at least three months at a high enough temperature (about 80º) for there to be no residue left when it’s applied to crops,” Sachse said. When composting, farmers will need to turn their piles at least once a month, but the more they are turned, the better.
Why compost horse manure? Sachse listed many reasons: It decomposes medical residues as well as carbonaceous materials; it kills weed seeds and parasite eggs and larvae; and it reduces runoff. It also prevents the leaching of ammonium or soluble nitrogen, and after the three months of aging, nitrogen becomes more plant available.
In addition to turning the compost, though, it also needs to be covered to prevent runoff. At Pinsch of Soil, they use a four-bin system (each bin measuring 8x8x12) covered with a metal roof. Its concrete base extends out far enough to park all four tractor wheels on it for mixing and moving purposes. Sachse said with 10 to 12 horses, it takes about one month to fill one bin. They make sure to turn the manure/compost mixture often enough to add oxygen and keep at about 50% moisture.
“We haven’t had to haul any manure away since constructing the bins in 2013,” he said.
Composted horse manure has decent amounts of nitrogen, phosphorus and potassium as well as micronutrients for plant growth. Pinsch of Soil Farm’s carbon-to-nitrogen ratio is about 8:1, which is low for a balanced compost. When used as a crop application, a C:N ratio of 20:1 is better compost. It’s always wise to test your soil first to see exactly what it needs, though. If the carbon content is low in the compost, farmers can increase it by adding more high-carbon materials (anything really woody).
“It’s better to adjust the C:N ratio after removing the compost from the bins,” Sachse said, such as adding wood chips on top of spread compost, or mixing in leaves and wood chips as it’s applied.
The longer a farmer can age manure compost, the better. Ideally, the mix should be applied to the fields about one month before planting to stimulate soil activity. However, if fresh manure needs to be used, Sachse recommended incorporating it into the soil as soon as possible and applying it at least four months before harvesting any crops that may come into direct contact with it.
Horse manure compost is a very good source of organic matter. It also increases the water-holding capacity of sandy soils and improves the drainage of clay soils. Even better, it promotes the growth of beneficial soil organisms too.
As previously mentioned, different livestock have different digestive systems, so take into account if planning to compost manures together. Chickens don’t produce urea like mammals do. And sheep, llamas and alpacas digest their food better than horses, so their manure is more easily and safely applied fresh to fields.
by Courtney Llewellyn