Horse Manure: Too Much of a Good Thing?

Dr. Susan Kerr, WSU NW Regional Livestock and Dairy Extension Specialist

The recommended initial Carbon to Nitrogen ratio in a compost pile is 25:1 to 40:1. Horse manure with bedding is about 30:1

Where there are horses, there is poop. Improperly managed manure can be an environmental and social nightmare by drawing flies, emitting odors, decreasing water quality, and encouraging parasites. Well-managed horse manure can control these undesirable elements and produce a valuable soil amendment, as well.


Composting takes space, labor, and commitment, but it is well worth the effort. Composting facilities can be made at little or no cost with recycled materials or cost thousands of dollars, depending on an owner’s resources, needs, and goals. It is best to start a compost pile on an impervious surface such as concrete to reduce nutrient run-off. Covering the pile will prevent run-off due to excess water and help keep the pile from drying out.


Effective composting requires the right proportion of carbon, nitrogen, water, oxygen, and composting organisms. It is best to mix the pile periodically to be sure all contents reach the proper temperature to kill most weed seeds, pathogens, and parasites. Water may need to be added periodically, especially in windy locations. A compost thermometer and record book will help with proper compost pile management—strive for temperatures between 131 and 149°F for three days; less than 131°F is ineffective at killing pathogens and greater than 149°F kills beneficial composting organisms.



Fortunately, there are many excellent resources available to horse owners striving to become effective manure managers:

• Local Conservation Districts and/or USDA Natural Resource Conservation Service (NRCS) offices can be of great assistance in creating manure management plans. They may have cost-sharing funds to help establish or upgrade on-farm composting facilities, too.

• An upcoming webcast will focus on composting horse manure. It will include information for large and small-scale horse farms about the effects of bedding on compost and compost facility design. The program will be presented at 11:30 AM Pacific Time on June 19 at Viewers should go to before the event to ensure access capability. The program will be archived and available for future viewing at

• Manure Management Strategies Webinar (archived) – “Help Your Horse, Help the Farm AND Protect Our Water” from My Horse University and eXtension HorseQuest:

• Making and Using Compost from University of Missouri Extension:

• resource area:

• Horse Manure Management article:

• NRCS Manure and Nutrient Management:

• Composting to Reduce Weed Seeds and Plant Pathogens article:


It costs money to feed a horse, so why not benefit from the major by-product of feeding? Properly-composted manure can replace fertilizer, improve plant health, increase soil organic matter, enhance soil microbial action, and increase nutrient cycling. Home gardeners are always on the look-out for weed-free compost, as well, and many are willing to pay for it. From now on, consider horse manure as “black gold” in the ma