Like HowStuffWorks on Facebook!

Garden Soil Tips


Test Your Soil

Before you start adding fertilizers and amendments to your garden soil, you need to determine what type of soil you have. 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. The following tips will help you test your soil.

  • Call your local Cooperative Extension Service, often listed under federal 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 infertile above pH 8. Excessively acidic and alkaline soils can be treated to make them more moderate and productive.
  • 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 diseases or worse. Buy only what's required and save the rest of your money for a better use, like more plants.

    Check your soil's texture with a simple test you can do at home.
    ©2007 Publications International, Ltd.
    Check your soil's texture with
    a simple test you can do at home.

  • 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. Gather up some soil from the garden, choosing a sampling of soil from near the surface and down to a depth of 8 inches. Let it dry, 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 of powdered dishwasher detergent. (Dishwasher detergent won't foam up.) Add enough water to fill the jar two-thirds 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. Set an alarm for 4 hours, and when it goes off, mark the next level, which is the amount of silt that has settled out. Over the next day or two, 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, or 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 more moisture, so it takes longer to dry in spring and may need less watering in summer. It can be richer and 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 thick and poorly aerated.Soil that has more 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.
    • Over 4 hours: Drainage is poor and needs help.

Now that you've determined your soil type, find out more about making changes to create the best soil possible for your environment on the next page.

Want more gardening tips? Try:

  • Gardening Tips: Learn helpful hints for all of your gardening needs.
  • Annuals: Plant these beauties in your garden.
  • Perennials: Choose great plants that will return year after year.
  • Gardening: Discover how to garden.