Yardsmart: The value of manure as fertilizer

Maureen Gilmer

From the moment the good manure is buried, its subterranean life begins: millions and millions of microbes, fungi and fermentation begin the work of attacking the hardest pieces; lime, sand, clay, organic matter of all sorts, they select, digest, secrete. -- Fernand Lequenne, "My Friend the Garden," 1941.

I have always gardened with manure, just like untold generations before me. I do not have much compost, but am rich with this earliest form of fertilizer in agricultural history. When taken from the stable and distributed into gardens, the cycle of life is completed. For me, using free manure makes a garden and lifestyle greener. Best of all, it's cheap.

Unfortunately, the benefits of manure have been overlooked in favor of bagged or homemade compost. Bagged compost is expensive, and my home composting generates too little to sufficiently feed a sizable garden. While compost is an ideal soil amendment, it is not the only one.

As backyard food gardeners expand from a small raised bed to a large tilled area, they find that the cost or availability of compost may limit their potential. Over the span of each growing season, soil microbes consume a lot of the organic matter you applied in spring. Therefore, it must be done again each year to keep fertility high. Maybe it's time to bring manure into your garden. After all, manures from all farm animals are applied today on small European farms, just like they were centuries ago.

The downside to manure is that it contains seeds that pass through a horse intact. Fewer exit a cow because it has three stomachs and is better able to digest seeds. This is why manure can introduce weeds to your garden. In its long journey through the digestive tract, ground-up hay picks up all sorts of bacteria, fungi and microbes. The result is the holy trinity of organic soil: nitrogen, organic matter and microbe loads make manure a powerfully holistic soil builder.

Horse owners have a manure problem -- there's just too much of it. One horse produces up to 50 pounds per day. When it builds up on site, it's not environmentally beneficial. Rainfall carries runoff from manure piles to pollute rivers and groundwater. That's why equestrians need to get rid of manure and gardeners need to find more of it. When these two special-interest groups come together within a community, there's an opportunity to solve problems on both ends simultaneously without money changing hands. That is the essence of sustainability created through cooperation.

Horse manure has two basic forms. That which is relatively pure is the more fertile form that can be composted and aged so viable seeds are heat-killed, but this is neither a quick nor foolproof process. Some weed seeds will survive. This form is also ideal for extending scanty compost with finely textured nitrogen-rich material.

The other form is manure from stalls bedded with straw or wood shavings, which resist decomposition. Such woody organic matter isn't great for small gardens, but it's perfect for opening up heavy clay soils on a large scale to increase oxygenation and drainage. This form is not particularly fertile unless enhanced by another source of organic nitrogen such as alfalfa meal.

My dream is for gardeners and equestrians to come together in an effort to improve soil for gardening and protect the environment by distributing manures far and wide instead of in large concentrated piles. When gardeners help a horse owner with manure management, the result is larger gardens with more diverse microbe populations and greater overall fertility. Facilitating this partnership would be an ideal project for any group devoted to protecting animal rights and the environment while promoting slow food at the same time.

So when you're faced with fortifying a big food garden worn out from too many years without enough compost, bring in manures. After all, it's Mother Nature's best effort at creating a perfectly designed fertilizer.

Maureen Gilmer is an author, horticulturist and landscape designer. Learn more at Contact her at or P.O. Box 891, Morongo Valley, CA 92256.