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Gardening: Beneath Our Feet

Where we came from, where we're going and where we spend a lot of time

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Hidden in these long columns of dirt is practically all the information one might need to figure out what a particular summer day was like 35,000 years ago. Temperature, air quality, variety of plant life, environmental cataclysm such as volcanic eruptions and comet impacts: These all leave clues on the ground that get buried by the next batch of information and filed away by the earth for future reference. When we bury time capsules, it's sort of redundant.

So your soil is really trying to tell you some things. And if you're the kind of person who's trying to grow stuff in that soil, it's a good idea to listen.

First, what is soil? Ah, yes, it's a little tricky to know exactly, because there's so much going on beneath our feet. Soil's what happens to mountains and oak trees and squirrels and that sock you lost in the woods when you were a teenager in the bloom of first love — plus the microorganisms that live down there, and air and water to varying degrees. The relationship of air to water is really one of the hallmarks of good soil. If you can keep both of these moving constantly through your soil, many other problems will clear themselves up. All these elements are caught up in the big cycle of reclamation that makes way for new trees and squirrels and, eventually, socks.

There are five physiographic regions in Virginia: the Coastal Plain, the Piedmont, the Blue Ridge, and on the other side of the mountains, the Valley and Ridge — the breadbasket of the state, where the grass really is greener — and the Appalachian Plateau.

Those first two regions come together in Richmond, making things tricky. The Coastal Plain in the east sits close to sea level, has a lot of sand and is shot through with rivers running out to meet the Chesapeake. Moving west is the Piedmont, characterized by slopes, water running down hills and a lot of stone. The border between these two zones is the fall line, a ticklish area identifiable as the place where falls and rapids pop up in the rivers. In other news, Richmond has great white-water rafting. So when it seems like your neighbor across the street has a whole different soil type and a whole different set of problems, blame the settlers who couldn't get their boats over the darn rocks.

Five regions, three particles: big sand, smaller silt, tiny clay. An even mixture of all three is loam. Sand tends to keep air flowing through the soil and clay can be pretty fertile, but too much of any is problematic. Take montmorillonite, for example, a particular type of clay that has a lot of uses in industry and cosmetics. It expands dramatically when water is added, and high concentrations in the soil can cause shrink-and-swell damage to foundations. Before the hurricane disasters last year, FEMA spent more money on repairing shrink-and-swell damage than on anything else, which says a lot about clay — and about FEMA, I guess.

But back to the disaster site that is your yard. Those three particles — sand, silt and clay — can be present in various concentrations, with names that reflect both the type of soil you have and the lack of creativity from the people who came up with the names: sandy loam, silt loam, silty clay loam, clay loam. The concentrations give you an idea of how long the soil will hold moisture (longer for the smaller particles) and how easily oxygen passes through it (sandy soils drain quickly and are more easily aerated), and they can help you predict what problems you'll face.

Good soil is like a rusty nail: Water and oxygen react with the iron in it, breaking it down and giving it that red color. The red indicates the soil is healthy and doesn't have problems with wetness and drainage, like yellow or gray soil might.

But like those chilly fellows scrutinizing samples of Antarctic soil for a better understanding of how the earth behaves, figuring out what's going on with the soil out your back door should use the science at our disposal.

Soil testing is a good idea before starting any big gardening project and after adding amendments. A good time to test is late summer or early fall so that fertilizer can be added or pH can be balanced and given time to settle in before spring. Virginia Tech and Virginia State University test soil from all over the state, sent to them in little boxes that look like they should be carrying lemon chicken rather than silty clay loam. Some garden centers test too, but local Virginia Cooperative Extension offices can walk you through the process, and you'll end up with an individual plan for your soil so that someday, 35,000 years hence, some future scientist will pull up a sample from your yard and say, "Wow, they really had healthy soil back then. Right before that comet hit." HS



Who Can Help

The extension office in Richmond is at the East District Center in Church Hill, 701 N. 25th St., 1st floor, at the corner of 25th and M streets. (804) 786-4150.

In Chesterfield County: Chesterfield County Government Complex, 6807 Mimms Loop. (804) 751-4401.

In Henrico County: Henrico County Human Services Building, Western Governmental Complex (just off Parham Road), 8600 Dixon Powers Drive, 2nd floor. (804) 501-5160.

In Hanover County: 13224 Hanover Courthouse Road, Suite 204. (804) 752-4310.

And where the magic happens: Virginia Tech Soil Testing Lab, 145 Smyth Hall (0465), Blacksburg. (540) 231-6893.

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