Documents: Special Interest: Organic Growing:

Don’t Tread On Me!
by Jim McLain
by Jim McLain


Jim McLain lives and gardens in the Yakima Valley of Washington state. He has been a vender at the Selah Farmers’ Market and has written gardening columns for two weekly newspapers.

Jim is presently the garden columnist for the Yakima Herald-Republic daily newspaper and contributes to the Yakima Valley Master Gardener column that appears in the same newspaper

September 5, 2010

Since September 11, flying the American flag in the United States has become very popular. I would suggest another flag that might be raised above your vegetable garden, regardless of what country you live in. But first, a little history is in order.
During the American Revolution, military units flew many different flags. One flag, with several variations, pictured a rattlesnake above the words, “ Don’t Tread On Me.” While this was a warning to the British, it might well be worth keeping in mind as you plan your next vegetable garden. 
As far back as the 1980s, Al Trouse’s research at the USDA’s National Tillage Machinery laboratory found that walking on your garden soil could restrict root growth by as much as nine-tenths of what it could be. Trouse found that a footstep taken on tilled soil exerts 3.5 pounds of pressure per square inch. If a gardener, weighing 154 pounds and with a heel area of 7 square inches, divides his weight by 7, he will find that he exerts pressure of 22 psi with each and every step taken in the garden.
Soil compaction begins even earlier--when we first spade or rototil our garden. This is contrary to what we have always believed about tilling soil. Turning over soil may be necessary, but many of us tend to till too much—to the point that we break down the soil’s structure. Every time we work in our garden, we cause the soil structure to be broken down further. 
Compaction lowers the penetration of air into the soil, and that prevents good root growth. At the same time compaction causes a decrease in the number of microorganisms inhabiting the soil whose job it is to change organic matter in the soil into nutrients that plants can use. Additionally, some microorganisms are responsible for stabilizing humus into a form that develops a porous structure that allows free movement of air and water through the soil.
You might be thinking, “Well, that sounds well and good, but unless I can walk on air or I inherit a hovercraft, all this information doesn’t do me or my garden much good.” The answer, however, is much simpler—using raised bed gardening does away with most compaction and leads to the development of better soil structure. 
Of all the benefits of raised beds, and there are many, I believe that preventing soil compaction and developing good soil structure are the two most important. The one cardinal rule of raised bed gardening is to avoid walking on the soil. If you design your raised beds so that you can reach comfortably anywhere into them from the walkways, there will never be an occasion when you need to tread upon your raised beds. 
Most of my vegetable garden is in raised beds. Although I grow corn and potatoes in traditional ground level rows, they could be grown just as well or better in raised beds. With the raised bed bug that has infected me for the past several years, my whole garden will likely be converted to raised beds in the near future.
In the last few years, you may have noticed articles and books promoting a no-till approach to vegetable gardening. Lee Reich’s book, Weedless Gardening (Workman Publishing) advocates discontinuing rototilling, plowing, and spading. His gardening method of “from the top down” advises us to continually replenish the soil’s surface with compost and mulch. The decaying organic matter will enrich the soil in the same manner that fallen leaves and needles do in a forest. Reich contends that only when we plant and transplant do we need to disturb the soil. Reich’s ideas could be the ultimate answer to avoiding compaction and maintaining good soil structure. 
It’s not my suggestion, however, that you sell your rototiller, retire your spade, or completely quit turning over the soil in your garden, but only to encourage you to avoid over-cultivation and to respect the integrity of your soil’s structure by not treading on it. 
Raised beds can be gardened year- after- year without treading on them and causing compaction. Your soil will thank you and reward you with an even more abundant harvest in your next garden.

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