English gardeners have a great expression for good soil: Earth that is in tiptop shape is “in good heart”: It’s alive, it’s healthy.
If you think of the soil being as much a living organism as a tree, you are on your way to gaining that elusive green thumb. The Martian terrain we have seen of late is a wondrous thing, but to the gardener it looks pretty barren. The absence of water, organic matter, microbes, nutrients and oxygen have rendered the ground desolate. On Earth, at least, adding those components produces a soil that will sustain verdant, vigorous and healthy plants.
The trouble is, looking at your garden soil presents little clue to its health. Holding it in your hand is a little more informative–dark, crumbly is good; light brown and doughy is bad. But the best way to gauge your patch is through a soil test. In the United States, this is done easily and cheaply, though far too few of us take advantage of the service.
The procedure itself is straightforward: Pick up or arrange the mailing of a soil test kit from your county extension office or elsewhere, take a soil sample, send it off with a payment and wait a couple of weeks for the results and recommendations for fertilizing, liming and soil amending.
Now is one of the best times to do this so that you can get your soil “in good heart” by the time your plants want to grow in April and when you want to add new delights. If your ground is frozen, wait for it to thaw before taking samples.
Typically, a basic soil test measures the presence of nutrients fundamental to plant health, including potassium, phosphorus, calcium and magnesium. Nitrogen, though vital, is not measured because it is so transient. Assume your turf and garden plants will need a periodic dose (though not too much–excessive amounts run off to pollute streams and rivers).
The basic test also includes a measure of the soil’s pH, or acidity-alkalinity. (pH measures hydrogen ions and stands for potential Hydrogen).
Some plants like acidic soil–azaleas, camellias and blueberries among them–but even they can find their roots in ground that is too sour. Sometimes gardeners go overboard in trying to fix this. Automatic liming year by year or excessive use of wood ashes inevitably leads to soil that is too alkaline, said Steve Heckendorn, manager of the Virginia Tech Soil Testing Laboratory. Excessive fertilizing is bad for plants too.
“Too little is bad, too much is bad,” he said. “That’s why you want to get a soil test.”
Most labs charge extra for measuring the organic matter in soil, but this test is invaluable in assessing the state of your soil. Organic matter, gardeners call it humus, is the soul of the soil: It creates a structure that retains moisture and air, vital for root health, and also draws earthworms, other beneficial creatures and microbes that feed and invigorate plants, protecting them against pests and diseases. Horticulturists look for an organic-matter content of at least 2 percent.
You can add finished humus with homemade compost or allow shredded leaves or other organic mulch to break down over several months. If you don’t have a compost pile, you can dig in peat moss or bags of rotted manure, available at hardware stores.
Another important element in the test is the cation exchange capacity (CEC), which measures the soil’s ability to hold and release nutrients. The level should be at least 10; adding organic matter will correct deficiencies.
Basic nutrient shortages can be corrected with chemical fertilizers or, for the organic gardener, non-synthetic feed such as fish emulsion, kelp meal or processed animal manures, available at some hardware stores and most garden centers.
Soil-testing kits (an information sheet and cardboard box for samples) are available from your county extension service.
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Soil test can gauge your dirt’s health
1. Look your yard over. Each sample should reflect a specific growing condition, e.g. lawn, vegetable garden, trees and shrubs. You may want to get two or more tests of your property.
2. Avoid sampling very wet soils. Do not sample recently fertilized soil.
3. Using a clean spade, obtain soil from the surface through the primary rooting zone of the crop. For most plants, the top 6 to 8 inches is appropriate. For established grasses sample the top 3 to 4 inches.
4. Take 10 of these samples from the sampling area, place them in a clean container and mix thoroughly. Spread the mixture out on a clean paper to air dry (do not place soil in an oven).
5. Mix the soil again. Obtain a 1-cup measure of the soil mixture and place it in the box provided in the kit.
6. What you should test for in your soil:
Organic matter
Phosphorus
Potassium
Magnesium
Calcium
Soil pH
Cation Exchange Capacity
Zinc
Manganese
Iron
Copper
Boron
–The Washington Post
