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Working the Soil

To many gardeners, starting a new garden bed means using a rotary tiller. While a tiller is a powerful and helpful tool, tilling is not the best way to work the soil. Some vegetable gardeners use their rotary tillers several times during the season. They may till in a green manure crop in early spring, and then till again a few weeks later to make a fine seed bed for planting. During the season, they may get out a smaller tiller for weed control, and then till the garden under again in fall. While tillers seem convenient, their use gets costlier all the time as fuel prices increase, plus there's the environmental cost for the carbon dioxide they produce, and the damage they do to the living organisms in your soil.

Digging and Double Digging

Digging a garden bed takes considerable time and effort, but it's work well rewarded by more-vigorous, higher-yielding plants. Plants growing in deeply prepared soil also have deeper roots and are thus more drought tolerant.

Is It Ready to Work?

Tilling or digging the soil when it is either too wet or too dry is disastrous for soil structure. Wet soils will form large clumps when tilled. The clumps will dry hard and solid, without the many tiny pores that hold water and air in the soil.

Without air, root growth suffers. Cultivating soil that's too wet can also cause water to run off or sit in puddles on the surface rather than percolate down into the root zone. If your soil is too wet, let it dry before planting. Pick up a handful of soil and squeeze it. If it crumbles into smaller, light-textured pieces, it's perfect for planting. But if it forms a muddy ball, the soil is too wet to be worked. Wait a few days, and test again to see if it has dried out. Dry soils can turn to fine dust when tilled, which also destroys the structure you've worked so hard to build. If a handful of soil crumbles immediately to dust, water the site thoroughly and wait a day before testing it again. The traditional technique for preparing perennial garden or improving drainage on : poorly drained site is to double dig. This process improves the structure and fertility of the top 2 feet of the soil.

To double dig a new bed, start by marking off the edges of the bed and watering deeply several days before you plan to dig. Then follow the steps below:

1. Strip off weeds or sod. Discard roots of perennial weeds in the trash. Turn sod stripupside-down on the compost pile, or use them to patch existing lawn.

2. Dig a 1-foot-wide, 1-foot-deep trench along one edge of your site. Put the soil into a wheelbarrow or onto a tarp.

3. Loosen the soil at the bottom of your trench by inserting a garden fork and wiggling or twisting it around. Top it with a 1- to 2-inch layer of organic matter.

4. Dig a second 1-foot by 1-foot trench next to the first, placing the soil on top of the layer of organic matter in the first trench. Then loosen the soil beneath it and add another layer of organic matter.

5. Continue systematically down the bed, digging trenches and loosening subsoil. When you get to the end, use the reserved soil from the first trench to fill the final one.

6. Spread compost or other organic material over the entire bed, then use a spading fork to work it into the top 4 to 6 inches of soil. The amount of organic material you add can vary, but 2 to 3 inches is adequate.

When you double dig, lavish most of the organic material on the topsoil. Add only small amounts of compost or chopped leaves to the lower soil layer because the rate of decay is much slower in the second 6 inches of soil than it is in the top 6 inches. Double digging your beds will raise them about 3 to 4 inches because it thoroughly loosens and aerates the soil.

Double digging is hard work. If you have back problems, it's probably best not to double dig your garden. And if you've never tried double digging a bed before, start small. Try working a 3-foot by 3-foot bed, and build up from there. And remember, you don't have to dig an entire bed in one stint -you can spread out the work over several days or a few weekends.

Another method for improving soil, that's less work than double digging, is single digging. In this case, you loosen the soil to a shovel's depth-about 6 inches and incorporate organic matter in that portion of the soil. Yet another option is to single dig, then create a raised bed on top of the prepared soil.

Tilling or hand digging, no matter how care-fully done, has a major impact on soil microorganisms. When you turn the soil, you add an enormous amount of oxygen to it. This creates an environment primed for an explosion of microbial activity. In most soils, more than 80 percent of the aerobic bacteria are present in the top 6 inches; more than 60 percent are in the top 3 to 4 inches. If you add organic matter as you till, you supply fuel for the population explosion, and your soil will remain in balance. On the other hand, if you till repeatedly, thus increasing the microbial population, you'll speed the decomposition of your soil's organic reserves and soil organic matter levels will decrease.

So for your soil's and plants' sakes, don't use a tiller unless you really need it. Instead, hire a neighbor's teenage daughter or son to dig a new garden bed if you can't do it yourself. Once a bed is dug, keep the soil loose and healthy by relying on mulch to reduce weed problems and conserve soil moisture, by avoiding walking on beds, and by cultivating shallowly when weeds are small.

Erosion on the Home Front

The loss of topsoil through erosion isn't just a problem on farms and at construction sites. Erosion can happen in our own front and back yards. Take these steps to minimize soil erosion around your home:

• On slopes, build terraced garden beds, or at the least, be sure your garden rows run across the slope, not up and down.

• Don't leave sloping areas unplanted.

Plant groundcovers, vines, or other plants with spreading roots and top growth that will hold soil in place.

• Mulch permanent pathways with stone or a thick layer of organic mulch, or plant a durable groundcover or lawn grass.

• In fall and winter, mulch bare vegetable or flower beds, or plant a cover crop to prevent wind or water erosion.

• Keep areas cleared for construction well mulched with straw. Try to minimize the use of heavy equipment.

Soil compacted by machinery cannot absorb water well; the runoff will carry valuable soil with it.