Animal manures are an excellent source of nutrients for our gardens and help improve soil structure. But which ones are best? Cattle? Sheep? Horse? Also, find out why manure should be composted before use and what to know before you buy.
Also see Is Wood Ash Good for the Soil? and How to Grow Cover Crops for more soil enhancing ideas.
Choosing Manure for Your Garden
Have you ever stood at the garden supply store looking at various composted animal manure products and wondered which one is best for your garden? Or passed a roadside stand and wondered if alpaca manure is calling your name? Or you have a friend who swears by a load of aged horse manure?
Manure is a popular soil amendment for several good reasons: it’s an organic fertilizer and soil builder all in one, comparable in nutrients to plant-based-only composts.
Manure helps maintain a healthy level of organic matter in your soil while also improving soil structure. And that, in turn, provides a better home for microorganisms which in turn release nutrients for our plants. That same organic matter also improves the soil’s ability to hold water and air.
And, like other slow-release fertilizers, some of the nutrients in manures are immediately available while the rest become available over time as more compounds break down. Manure for the win!
Manure Options
At our local stores, the options tend to be mass-produced composted cow and sheep manures in plastic bags. And farmers in the area also offer various raw or aged horse, alpaca, llama, and chicken manures.
The first decision is simple: avoid raw or aged manures unless you have the knowledge and resources to safely manage the long-term, hot composting process.
These manures carry pathogens like E. coli, Listeria, and Salmonella, weed seeds, and antibiotics, along with pesticide and herbicide residues. That’s quite a list. If composted properly (reaching the necessary heat levels of ≥130° F), the risks are greatly reduced.
Rabbit manure seems to be one that can be applied directly on the soil without composting unless it is urine-intensive and too high in ammonia (your nose will tell you).
But for all other animal manures, error on the side of caution and only use them when completely composted.
Which Ones Are Best?
When I started researching this I assumed I’d learn that certain manures are appropriate for certain soil conditions, but what I found is, at a nutritional level, there is little difference between them.
Yes, it’s good to have your soil analyzed and know what your soil needs but once you do, the main decision for manures goes beyond the animal species that pooped it.
According to the product labels and research, all of these manures provide some nitrogen, phosphorus, potassium, and various micro-nutrients.
Chicken manure is known for its higher nitrogen levels—which can be desirable—and their tough digestive systems tend to destroy any seeds ingested (fewer weed seeds), but it may not be so affordable to get it in the volumes needed. I don’t see it in big bags like the cow and sheep manures.
Horse manures are most closely associated with herbicides so knowing more about food sources for the animals is important before ordering a truckload.
The question with alpaca and llama manures is: are they truly composted or just aged? These guys gobble up a lot of weeds so you want to be sure those weed seeds are toast.
And, if you’re racking your brains to determine the difference between cow and sheep manures—it’s negligible. Whichever one is on sale wins!
But, that said, there are other factors you may want to consider first.
Questions to Consider
Here are some ethical, environmental, and practical considerations.
- Are herbicides present in the manure?
This is a big one. And it may not be easy to get reliable answers. For all the good composting does, it may not destroy all herbicides present and tainted compost can destroy your garden.
- Has it been properly hot composted?
If so, there are much better odds that any pathogens and weed seeds have been destroyed, although there’s always the chance that some remain. And again, herbicides may persist.
- Does the manure come in thick plastic bags that just go to landfill?
Could I get a comparable product delivered without the bags?
- What do the animals eat? How are they treated? Is this a business I want to support?
- What type of bedding is used?
The bedding material inevitably ends up mixed in with the animal waste.
- Is it local and affordable?
I find the most reliable source for composted manure, mulch, and top soil is a local landscaping design business that uses the same products for their clients. It makes a big difference when their reputation depends on it.
Is This Composted Manure Healthy?
As mentioned, when manure is combined with other organic matter and thoroughly composted, you end up with a beautiful, earthy soil.
I’ve used a lot of different manures over the years and every once in a while there is a problem.
The first clue is the smell. If the manure is properly composted, it will not have an unpleasant odor. It should just be like any other healthy, moist soil.
If it has a bad odor or smells like animal waste, it’s not ready for the garden. Depending on circumstances, you may choose to compost it yourself or return it.
Another problem I hear now and then is mold or fungus growing in the bagged products.
That’s another situation where I would return everything to the store and start over with a different lot.
Herbicide Test
If you’re worried that herbicides may be present, before ever using the composted manure in your garden, test it.
Tomato plants are very sensitive to selective herbicides such as aminopyralid which is used to treat broadleaf plants—plants that some of these manure-producing animals may consume.
Try a side-by-side comparison germinating seeds in 5 pots of your composted manure and 5 pots of potting mix.
Use seeds from the same pack and provide identical, good growing conditions.
If there is a problem with the manure, your seedlings will tell you with a wilted appearance and odd leaf formations.
Precautions like this are worth the time if you plan to use the manure on a significant portion of your garden.
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