Horse manure good for your garden and usually cheap or free

Call me crazy, but I just love the smell of horse manure. Not only does it grow fabulous plants naturally, it's typically cheap or free.

Most horse owners are keen on getting it off their property as soon as possible, and will thank you for hauling it away in gunnysacks or a pickup truck.

I recently heard a lecture about the value of horse bedding. This is a combination of wood shavings and manure that comes from racetracks, corrals and stables. Horse bedding is highly variable, which has a big impact on how well it works in your garden. It's all about the proportions of shavings to manure in the load.

Your existing soil is composed of millions of microorganisms that feed on organic matter such as dead leaves. They are nature's way of breaking down fibrous material into humus, a fine substance useful to plants. The process of composting achieves the same result.

It works like this: A thin autumn leaf is very easy for microorganisms to digest. When they attack a thick leaf, it takes more energy in the form of soil nitrogen to digest it. Even heavier organic matter such as wood shavings take proportionately more energy and time to become humus.

If microbes lack enough energy to fuel their digestive efforts, they seek outside sources of nitrogen to get the job done. Hungry, hardworking microbes find it in manure, but if this isn't enough, they take it from the surrounding soil. When they rob the soil, the result is a net loss of nitrogen, which is bad for both soil and plants.

For best results, seek out bedding with higher concentrations of manure. If that's not available, you can compensate by adding nitrogen fertilizer to the soil before mixing in the bedding. This gives a ready supply for the microbes and speeds up the decomposition process. Good organic sources of nitrogen include bagged steer or chicken manure, fish emulsion or nitrogen-rich organic fertilizer pellets.

The best thing about horse bedding is also the woody matter. Its slower decomposition means it hangs around a long time. If you have clay soil that turns hard as a rock or into a sticky quagmire, shavings are one of the cheapest ways to lighten it up. When you till the shavings into heavy soil, the woody matter holds it open to allow water, plant roots and fertilizer to penetrate deeper. That means you will have a healthier, more water-conservative garden this summer.

We tend to think that manure is a powerhouse of nutrients, which it is. But relative to manufactured fertilizers, horse manure is actually very low in nitrogen. It contains less than 1 percent nitrogen. Compare that with poultry manure, which contains a whopping 4 percent nitrogen, and you can see why this is a better additive to help your microbes cope with the shavings. Manure that's "hot" - right out of the animal - is not suitable for gardens. It is best aged or composted, which is how bagged manures are sold. Thus, older horse bedding will be more desirable than that freshly removed from the stable.