Soil types vary from the extremes of constantly dry, nutrient-poor sand to 90 percent rocks held together with 10 percent soil to rich, heavy clay (which forms a slick, sticky, shoe-grabbing mass when wet, then dries to brick hardness). Fortunately, most soil conditions fall somewhere in between these extremes. Still, very few homeowners find they have that ideal "rich garden loam" to work with.
Soils can be amended with sand to make them looser and drier or with clay to make them moister and firmer. They can be given plentiful doses of organic material -- old leaves, ground-up twigs, rotted livestock manure, and old lawn clippings -- to improve texture and structure. Organic matter nourishes any kind of soil, which, in turn, encourages better plant growth.
Learn how to make the most out of the soil in your area by reading the tips that follow. The first step is to identify your garden conditions by having your soil tested.
Have your soil tested or do your own tests to determine if you have a light and sandy soil, a moderate and productive soil, or a heavy clay soil. Get a soil test before you start adding fertilizers and amendments to your garden soil. This follows the old advice, "If it ain't broke, don't fix it." Sometimes unnecessary tampering with nutrients or soil acidity can actually create more problems than benefits.
Soil tests tell you the nutrient levels in your soil, a plant version of the nutrient guides on packaged foods. They also note pH and organic content, two factors important to overall smooth sailing from the ground up.
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To obtain a good soil sample, dig down 4 to 6 inches in several different locations.
To have your soil tested, call your local Cooperative Extension Service, often listed under state or county government in the phone book. Ask them how to get a soil-testing kit, which contains a soil-collecting bag and instructions. Follow the directions precisely for accurate results. The results may come as a chart full of numbers, which can be a little intimidating at first. But if you look carefully for the following, you can begin to interpret these numbers:
- If the percentage of organic matter is under 5 percent, the garden needs some extra compost.
- Nutrients will be listed separately, possibly in parts per million. Sometimes they are also rated as available in high, medium, or low levels. If an element or two comes in on the low side, you'll want to add a fertilizer that replaces what's lacking.
- Soil pH refers to the acidity of the soil. Ratings below 7 are acidic soils. From 6 to 7 are slightly acidic, the most fertile pH range. Above 7 is alkaline or basic soil, which can become problematic above pH 8. Excessively acidic and alkaline soils can be treated to make them more moderate and productive.
© 2006 Publications International, Ltd.
Hand carry or mail the soil sample
to the testing lab for analysis.
Add only the nutrients your soil test says are necessary. More is not always better when it comes to plant nutrients. Don't feel compelled to add a little bit more of a fertilizer that promises great results. Too much of any one nutrient can actually produce toxic results, akin to disease or worse. Buy and apply only what's required, and save the rest of your money for a better use, like more plants.
Determining pH Levels
It is always best to choose plants that thrive in the pH of your existing soil. If you must alter the pH, follow the guidelines below.
- Use ground limestone to raise the pH of acidic soils. Limestone is nature's soil sweetener, capable of neutralizing overly acidic soils. It's best to add limestone in the fall to allow time for it to begin to dissolve and do its job. The amount of limestone you use will vary depending on the specific soil conditions. Simple home test kits, or a professional test, can be used to determine the soil's pH. If you dump limestone on soil randomly, you run the risk of overdosing the soil. Follow the guidelines on the limestone package or on a soil test.
- To lower the alkalinity and increase the fertility of limey and other soils with very high pH, add cottonseed meal, sulfur, pine bark, compost, or pine needles. These soil amendments gradually acidify the soil while improving its texture. Garden sulfur is a reliable cure when added as recommended in a soil test. It acidifies the soil slowly as microbes convert the sulfur to sulfuric acid and other compounds.
- Maintaining the new and improved pH is an ongoing project. Recheck the soil's pH every year and continue to add amendments as needed.
Check the texture of your soil in a jar filled with water. This test is simple to do at home and provides important information about your soil.
© 2006 Publications International, Ltd.
Knowing the texture of your soil can help you determine
which plants will grow well in your garden and how much care they will need.
Gather some soil from the garden, choosing a sample from near the surface and down to a depth of 8 inches. If you have dry clay, pulverize it into fine granules, and mix well. Put a 1-inch layer (a little over a cup) in a quart glass jar with 1/4 teaspoon powdered dishwasher detergent. (Dishwasher detergent won't foam up.) Add enough water to fill the jar 2/3 full. Shake the jar for a minute, turning it upside down as needed to get all the soil off the bottom, then put the jar on a counter where it can sit undisturbed.
One minute later, mark the level of settled particles on the jar with a crayon or wax pencil. This is sand. Five minutes later, mark the amount of silt that has settled out. Over the next hour or so, the clay will slowly settle out and allow you to take the final measurement. These measurements show the relative percentages of sand, silt, and clay -- the texture of your soil.
- Soil that has a high percentage of sand (70 percent or more) tends to be well aerated, ready to plant earlier in spring. But it also tends to need more frequent watering and fertilization than heavier soils.
- Soil that has 35 percent or more clay retains moisture well, so it takes longer to dry in spring and may need less watering in summer. It can be richer and is more likely to produce lush growth with just the addition of compost and, occasionally, a little fertilizer. The compost is important. It helps break up clay so the soil won't be too dense and poorly aerated.
- Soil that has nearly equal percentages of sand, silt, and clay can have intermediate characteristics and is generally well suited for good gardening.
Test your soil's drainage by digging a hole, filling it with water, and watching how quickly the water disappears. All the soil tests in the world won't do a better job than this simple project. It tells you how quickly moisture moves through the soil and whether the soil is likely to be excessively dry or very soggy -- neither of which is ideal.
When it hasn't rained for a week or more and the soil is dry, dig several holes that are 1 foot deep and 2 feet wide. Fill them to the top with water and keep track of how long it takes for the holes to empty. Compare your findings to the following scale:
- 1 to 12 minutes: The soil is sharply drained and likely to be dry.
- 12 to 30 minutes: The soil has ideal drainage.
- 30 minutes to 4 hours: Drainage is slow but adequate for plants that thrive in moist soil.
- More than 4 hours: Drainage is poor and needs help.
These soil tests may seem like a lot of work without much reward, but if your soil is working at its full capacity, your plants will bloom at their best as well.
Although they seem to grow everywhere, dandelions prefer fertile, often heavy soil. Likewise, other weeds favor certain kinds of soil. For instance, acidic soil can encourage the growth of crabgrass, plantains, sheep sorrel, and horsetails. Alkaline soil (also called sweet or basic soil) is favored by chamomile and goosefoot. Fertile, near-neutral soils can provide a nurturing environment for redroot pigweed, chickweed, dandelions, and wild mustard.
Even if you can't tell one weed from another, you can find out important information by looking at them closely. If a vacant garden area has few weeds taking advantage of the opening, the soil is likely to need plenty of work. If weeds are growing, but only sparsely, and have short, stunted stems and discolored leaves, the area may have a nutrient deficiency, and a soil test is in order. If, in newly tilled soil, weeds sprout up quickly in certain areas and more slowly in others, the weedy areas are likely to be moister and better for seed germination.
Now that you've learned everything you've ever wanted to know -- and more -- about your soil, take a look at the next page for how to prepare your soil for planting.