Some people work the soil with tillers. Others, with a fork or spade. Still others simply plop a plant in a hole. After all, dirt is dirt, right?
Perhaps this is the spring to gain a new understanding of the soil we garden in — not to make it more complicated but, perhaps, more successful.
Alan Stevens of Kansas State University likes to shatter some of the myths about working the soil. We talked to him and then asked some master gardeners to weigh in with their experiences, which pretty much mirror the expert advice.
– Dig it.
As soon as the soil is thawed and dry enough to crumble, if you did not add organic matter to garden beds in the fall, do so. Add as much organic matter as you can work in. Add nitrogen, too (if you added organic matter in the fall, it shouldn’t be necessary).
The best organic matter is Canadian sphagnum peat moss, Stevens says, because of its coarseness and large particle size. It is slow to decompose and acidic, and that helps lower the pH. On the downside, it’s expensive, and there is an ecological concern that the Canadian bogs from which the peat moss is being removed are being depleted.
Other types of peat moss — darker in color — are farther along in their decomposition when you buy them and are not as desirable, Stevens says. The lighter brown the peat, the less decomposed and better it is.
Other organic-matter options: compost, either the kind cooked in the back yard or cotton burr compost bought at the store, and manure if it’s well composted and doesn’t have weed seeds.
Gypsum, often advertised as a good supplement for clay soil, is advantageous only when soil has too much salt in it, Stevens says.
A product such as EnviroMax is touted as a good addition to clay soils, but Sedgwick County, Kan., extension agent Bob Neier says he’s seen no independent studies to indicate that it works. Whether your soil is clay or sandy, the main problem you have to worry about is compaction. That is the reduction of pore space in soil, and large pores are necessary so that oxygen can move through soil. Organic matter binds soil particles, creating aggregates that create pore space.
“Any soil has the potential to become compacted,” Stevens says. “Clay is easier to compact through poor management.”
– How can you tell if soil is compacted?
Neier gives these tests for degrees of compaction: If you find it hard to dig down 6 inches with a trowel, the soil is compacted. If you can’t get a screwdriver into the soil without pounding it, it’s very compacted. If you find it hard to dig in with your hands, it’s somewhat compacted.
Stevens’ advice for totally compacted soil: Rototill it and add as much organic matter as you can, for a number of years.
Even in good soil, organic matter should be added every year. In perennial and shrub beds, scratch it into the soil as much as the plants’ roots allow.
While a tiller is necessary in the case of heavily compacted soil, it’s not the best thing for soil in other situations. Anytime you till it’s harmful to the soil structure, “so doing it at all is less than desirable,” Stevens says. “However, there are times when the physical exertion to turn the soil with a garden fork is more excessive than people are willing to do.”
If you use a tiller, adding a lot of organic matter will help repair the damage.
Stevens gives this example to illustrate the damage that machinery — and other types of weight — can do to soil: A path worn into the grass in a school yard does not come mostly from the bottom of kids’ shoes wearing off the grass but from repeated walking compacting the soil so grass will no longer grow.
– So how much should people use machinery on lawns?
“The simple answer is as little as possible, because the weight of the machine as well as the operator will work to compact the soil,” Stevens says.
If you do till, do it “just basically enough to loosen the soil and to mix in the organic matter. Go as deep as possible. Avoid tilling the soil when it’s very dry or very wet,” doing the work when it’s moist to slightly dry instead.
An aerating machine can help compaction but is another destructive force if the soil is not compacted, Stevens says.
If you aerate, be sure to work organic matter into the holes you make in the ground, Stevens says. You can do this buy placing a thin layer of organic matter on the surface and using the back of a rake to work in the material.
If you are able to use a garden fork or spade to work the soil, Stevens recommends double-digging. Remove a layer of soil to the depth of the spade or fork, add organic matter to the bed and work it into the soil in the layer below. You then add back the first layer of soil, working organic matter through it. Do as much as you can, to your physical limits.
Pat Beckemeyer, a master gardener who lives in Wichita, Kan., has worked her garden beds both by tiller and by hand.
“The part of yard we had tilled, I don’t like it,” she says. “It leaves all the roots in, and it’s hard to do because we have all the trees. Once you double-dig, it’s beautiful.” Double-digging is falling out of fashion in some circles, though, and some soils can probably get by without it.
– Don’t dash out on the first warm day and expect the soil to be ready for you, however.
“Part of improving soil is doing it at the right time,” says master gardener Pat Longhofer of Wichita.
One of her first experiences with clay came when she and a neighbor hired college students to use spades to establish a vegetable bed for them. But it had rained beforehand. “It never worked,” Longhofer said of the bed.
If you work wet soil, you wreck the structure and harden it.
The test: Take a handful of soil, form it into a ball and squeeze it. If you can squeeze water out, it’s too wet. If you don’t get water but the ball doesn’t crumble when you try to break it apart, you need to wait a little longer. If the ball crumbles fairly easily, you can get to work.
