Recently, I received a call from a gentlemen concerned about the use of horse manure as fertilizer. Horses are prone to a host of parasites, and most horse owners regularly dose their animals with vermicides – medications toxic to intestinal worms and other insect pests. These medications pass through the digestive system. This prompted me to find out whether tainted manure may be harming our crops, our subscribers, or the environment as we use horse manure in our compost piles.
Fortunately, most research to date indicates that Ivermectin, the vermicide most frequently given to horses, breaks down quickly once it is excreted. Several studies have shown that Ivermectin degrades rapidly when manure is hot-composted or exposed to sunlight. At J R Organics, we hot-compost with piles set out in full sun.
This doesn’t mean that vermicides are safe to use as they can be fatal to certain breeds of herding dogs and to numerous aquatic creatures, can cause nausea, headache and heart irregularities if splashed onto human skin.
However, studies indicate that the toxins are neutralized through composting and are not transmitted to the plants.
THE TRANSFORMATIVE POWERS OF COMPOSTING
A pilot study by the USDA’s Agricultural Research Service found that as much as 75 percent of the antibiotics administered to beef cattle is excreted in urine and manure. But the antibiotic concentrations in cattle manure dropped by 91 to 99 percent after 28 days in a compost pile made of layered straw and manure.
Manure-based composts must be produced according to NOP (National Organic Program) regulations in order to be considered compost. The NOP requires that compost containing manure be produced following one of these methods:
- Compost must maintain a temperature of between 131° F and 170° F for three days using an in-vessel or static pile system.
- Maintain a temperature of between 131° F and 170° F for 15 days using a windrow composting system, during which time the materials must be turned a minimum of five times.
If the compost does not meet these requirements, it is considered “raw manure.” Raw manure must be incorporated into the soil no less than 120 days prior to the harvest of a product whose edible portion touches the soil (such as lettuce) or incorporated into the soil no less than 90 days prior to the harvest of a product whose edible portion does not touch the soil (such as corn). Application timing and compost production methods will be verified to these restrictions during annual inspections.
At J R Organics, we use the windrow system of composting, turning the compost five times within a 15 day period. Our method is subject to annual inspections by CCOF.