What Is the Best Manure Compost for Gardens? The Scoop on Poop

All manure is not created equal. Depending on the kind of animal, its age and health, its food, what kind of bedding is incorporated into the manure, and how it is collected and stored, the nutrients it contains can vary widely. Also, whether the manure is fresh, composted, aged, or dried has a great impact on its nutrient values. To really know exactly what it contains, you will need to get the manure tested.

Different Types of Animal Manure

The most common sources of manure are cows, horses, sheep, pigs, goats, and poultry. (Other animal waste is not recommended for use as manure or fertilizer today.)

Here are some values commonly assigned to different animal manures:

• Fresh cow manure, sometimes called moo doo, is about 17% organic matter, offers .3% nitrogen, .2% phosphorus, .4% potassium, and is 83% moisture. To add .2 pounds of nitrogen to a 100-square-foot garden patch, you would need to add 75 pounds of cow manure without bedding or about three 5-gallon bucketfuls. Composted manure has even less nitrogen, so you would need to add 200 pounds of it to have the same effect! Dried cow manure has much higher nutrient levels - 2% nitrogen, 2% phosphorus, and 2.4% potassium—so you could use much less, roughly 10 pounds per 100 square feet.
• Fresh sheep manure is about 32% organic matter, has .7% nitrogen, .3% phosphorus, and .9% potassium, and is 66% moisture. To add .2 pounds of nitrogen to our 100 square foot garden we would need to add 40 pounds of manure with no bedding or 50 pounds with bedding included. Dried sheep manure is 4% nitrogen, 1.4% phosphorus, and 3.5% potassium, so we’d need only 10 pounds per 100 square feet.
• Fresh chicken manure, sometimes called hen dressing, is 25-45% organic matter, has 1.1% nitrogen, .8% phosphorus, and .5% potassium, and is 55-75% moisture. Add 30 pounds of it, including bedding, to a 100-square-foot bed to get .2 pounds of nitrogen. Composted, it would have less nitrogen, so you’d need 70 pounds. Because it tends towards alkalinity, poultry manure is unsuitable for lime-hating (ericaceous) plants, such as rhododendrons, azaleas, camellias, blueberries, and heathers.

• Fresh horse manure, sometimes called road apples, is 24% organic matter, has .7% nitrogen, .3% phosphorus, and .6% potassium, and is about 75% moisture. To add .2 pounds of nitrogen to the 100-square-foot bed, we’d need to incorporate 65 pounds with bedding included.
• Fresh rabbit droppings, also known as bunny honey, are 33% organic matter, offer 2.4% nitrogen, 1.4% phosphorus, .6% potassium, and only 43% moisture. As little as 10 pounds would add .2 pounds of nitrogen to the garden.
• Fresh llama manure, also called llama beans, offers 1.5% nitrogen, .2% phosphorus, and 1.1% potassium. It would take 20 pounds to add .2 pounds of nitrogen to the 100-square-foot patch.

Fresh vs. Composted Manure

Fresh manure is less than 6 months old and has not been composted. Never use it to side-dress your plants! It has high enough nitrogen and ammonia content to burn them. The plants are not able to make use of all of the nitrogen, and along with it potentially damaging them, it is also a waste as most of it will be lost and can contaminate groundwater.

The USDA’s National Organic Program (NOP) has specific rules about the use of manure in organic gardening. Raw manure must be applied no less than 120 days prior to harvesting leafy crops or those that come in contact with the soil, such as lettuce, beets, carrots, and potatoes. For those that do not touch the soil, such as peppers or tomatoes, raw manure must not be spread less than 90 days before harvest.

For those like me who have a short growing season, this means fresh manure must be spread in the fall. Fresh manure also can contain harmful pathogens, including E. coli, salmonella, and listeria, along with lots of undigested weed seeds.

Bottom line: Either till raw manure into the soil at least a season before planting. Or, the manure must be composted fully and “aged” before you add it to the soil. 

Composting Manure

Composting manure will greatly reduce the risk of illness and can render the weed seeds incapable of germinating. If it doesn’t have a lot of bedding, such as straw, wood shavings, or sawdust mixed with it, add leaves, grass clippings, food waste, or newsprint to increase the ratio of carbon to nitrogen to between 25:1 and 40:1 for the best results. Make sure your pile reaches high temperatures (131 to 170 degrees Fahrenheit) for at least a week, then add limestone, turn and aerate the pile, and let it cure for 2 to 4 months before using it to cut bacteria risks.

The nutrient values in the composted manure will be lower than in the fresh manure, but it will still supply your soils with organic matter, beneficial micro-organisms, and trace minerals, including calcium, boron, magnesium, copper, sulfur, zinc, and iron. To learn more about the safe use of manure in your garden, check out this tipsheet.

See our guide about preparing your garden soil for planting!

And here’s a post specifically about preparing the soil in the fall for next year’s garden. Fall is the best time to improve your soil!