Annie Calovich

October 8, 2011

Get the dirt on compost

I planted a couple of evergreen shrubs this week — weather, don't turn cold on me now — and, in the process, I dug up what we called "dirt clods" when I was a child.

I planted a couple of evergreen shrubs this week — weather, don't turn cold on me now — and, in the process, I dug up what we called "dirt clods" when I was a child.

I grew up in one of the first houses built in a new housing development, and, as other houses went up, there were plenty of dirt clods in our world. I remember them being a common part of our playtime conversations, but the only specific thing I remember is that ornery neighbor boys would throw them.

As a gardener, I haven't come across the term "dirt clods." "Clods in the soil" is the more elegant term I run across. Either way, they hold a negative connotation.

In the spring, when you work in wet soil, you form clods that last through the growing season, horticulturist Ward Upham of K-State Research and Extension says. But the situation is more forgiving in the fall. Clods that are formed now break down in the process of freezing and thawing during the winter, he says, "leaving a mellow soil the following spring."

Ah, a mellow soil. The breaking down of organic matter into the soil during the fall and the winter, making for ready-to-go planting in the spring.

The Canadian Sphagnum Peat Moss Association recently reported that the peat-moss harvest in Canada was hurt significantly this year because of heavy rain. Peat moss is one of the organic materials recommended for working into soil, especially into clay, to improve its texture. But extension agent Bob Neier says the use of peat has been declining as people turn to compost. Compost is the more sustainable choice, he says. And if you make your own, of course, it's free.

"Generations of research have backed up compost's benefits for everything from heavy clay to sandy soils," says Jennifer Smith, another horticulturist with K-State.

But I learned from her that there are differences in store-bought compost that, if you go that route, you may want to know about.

For example, cotton burr compost, a byproduct of ginning, has sulfur added to it if it's labeled as acidified. That can improve plants' growth if your soil pH is above 7, Smith says.

A couple of other kinds of compost, mushroom compost and worm castings (vermicast), should be used sparingly until you're sure of how a batch affects your plants, she says.

Mushroom compost is described as a variable mix of organic materials that were previously used as the growth medium in mushroom farming. This compost can contain a high amount of soluble salts, Smith says. Over time, the salts will leach away in the rain.

Worm castings will vary depend on what the worms ate, Smith says. It could have been vegetable scraps or salty sewage sludge. Again, she says, use the worm leavings sparingly until you're sure they're not hurting any of your plants.

You can also buy composted manure in bulk from such places as Singletree Stables, at 2100 E. 45th St. North. Singletree's compost — used in Botanica's new children's garden — contains horse manure, hay and wood shavings that had been used as bedding installs. It's fully composted and contains no pesticides. (See accompanying box for more details.)

Back at the ranch, there's no shortage of leaves, old plants, grass clippings, rotting hay and other garden debris that, if left out of the landfill, will become compost. Toss in non-meat and non-dairy food scraps and it's even better.

"Working the debris into the soil is easier if you mow the old vegetable plants several times to reduce the size of the debris," Upham says. Same with leaves.

You can make a compost pile with your materials, watering it and turning it every now and then, waiting for it to break down before moving it to where you want to work it into the soil.

"As a general rule, add 2 inches of organic material to the surface of the soil and till it in," Upham says.

You can also pile up your materials right where you want to plant in the spring, digging it in or not. It will eventually break down.

If tilling your compost in, "be careful not to over-till," Upham says. "You should end up with particles the size of Grape-Nuts or larger. If you work garden soil into the consistency of dust, you have destroyed the soil structure."

Just like with our old dirt clods.

"If that debris is worked into the soil," Upham says, "insects will be less likely to survive the winter. Diseases are also less likely to overwinter if old plants are worked under. Also, garden debris will increase the organic-matter content of the soil."

Just like the peat moss does. Except maybe it's time we strengthened that trend of making it at home.

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