Building Great Soil (cont)
By: Warren Schultz
Of course, using compost is another very effective way to improve the soil. Where clay rules, says Denny Schrock, the best thing you can do is add organic matter. "You can use composted manure, homemade compost, municipal compost, sawdust composted with manure--they're all good products. If you work in a good amount in the spring, it will improve the soil structure when you're planting." It's important to use only finished, completely decomposed, compost in spring.
How much is a good amount? "There's no such thing as too little," Schrock says. "Every little bit helps." But it is possible to add too much organic matter, especially to clay soil. "The problem with too much organic matter in the soil is that you can get shrinkage (a condition that occurs as the organic matter decomposes and the soil literally shrinks, resulting in cracks), and you'll wind up with huge gaps in the soil." So, as a rule of thumb, Schrock says don't add more than a third of the volume of the soil at any one time. "For example if you're going to work the soil to 6 inches deep, add a 3-inch layer of organic matter, and work it in thoroughly." What's the best way to work it in? "Get someone else to do it for you," Schrock quips. Failing that, you can use any tool, from a spade to a tiller.
Raise the Beds, Dig the Soil
Working amendments into the soil offers a good opportunity to build raised beds. "Raised beds offer several benefits," says Denny Schrock. "In heavy clay, just raising the soil helps to improve drainage." Those beds can be as simple or elaborate as you choose. "In my vegetable garden, I have what I call temporary raised beds," Schrock says. "I just dig out the walkways and mound up the soil between them. That way I can change the configuration from year to year. But in a perennial flower bed, you might want something more permanent and decorative. You can use landscape timbers for a more rustic look, or you might want to use interlocking concrete blocks."
Though he knows it can benefit the soil, Schrock doesn't bother with double digging. "I always say it's a wonderful thing to do for anyone with a weak enough mind and a strong enough back. It certainly helps, but it takes a lot of work." However, he suggests a double-digging shortcut you can use when constructing raised beds. "You can dig the first (original) layer of soil as you normally would," Schrock says. "Then add a layer of amended soil, and work that in thoroughly through the original layer of soil to root depth. It's important that the organic matter is worked all the way through the soil, or you'll wind up with a perched water table." Simply tossing on a layer of organic matter can actually result in problems: layers of wet and dry areas with different porosity prevent water from penetrating the soil uniformly.