Organic Matter and Soil Amendments
Part 3 of 4
Reduce Human Pathogen Risks
Fully composted manure can be applied to the soil at any time of the year. Manures are considered fully composted when a static, aerated pile reaches at least 131ºF. for 3 consecutive days. This kills most plant and human diseases. Temperatures >145 ºF. will kill weed seeds. Not all farmers actively manage and monitor their manure to this standard. So, it’s best to treat any local animal manure as un-composted and add it to gardens in the fall.
You can safely mix un-composted manures (ranging from fresh through well-decomposed) into the topsoil in fall and then cover the soil with mulched leaves, if possible, to reduce leaching, run-off, and erosion risks.
You can also spread and incorporate un-composted manure during the growing season at least 90 days prior to harvesting crops with edible parts off the ground (pepper, tomato, corn, eggplant) and 120 days prior to harvesting crops with edible parts touching the soil (leafy greens, root crops, bush beans). These guidelines reduce the likelihood of un-composted manure contacting your food. And, of course, always wash produce prior to fresh eating or preparation.
An excerpt from the article “Organic Matter and Soil Amendments“, courtesy of the University of Maryland. Author: Jon Traunfeld, Director HGIC, Extension Specialist, Fruits and Vegetables.