Soil Test and Amendment Guide
A soil test is a way of finding out more about the nature of your property’s soil, so you can choose appropriate species to plant, as well as the right amendments – remedies to help your yard produce healthy plants, trees, and grass. Soil testing is especially useful if you: 1) would like to revive a droopy, dreary lawn or garden, 2) are about to start planning next spring’s plantings, or 3) have just moved into a home and would like to better understand the soil you’ll be working with. Here are several DIY methods of testing soil. Try these fun and fascinating hands-on science lessons with a child if you can!
The first type of soil test doesn’t require bells and whistles, just a trowel and your bare hands. On a day when the ground is not soaked by a recent rainstorm or overly dry, dig down 10 inches. Bring up a trowelful of earth. Squeeze it in your hand. This simple soil sampling will tell you whether you’ve got:
- Loam, which holds its shape but crumbles when poked gently. This is the most desirable soil texture.
- Sandy soil, which does not hold its shape at all. It will benefit from amendment to increase water retention and nutrient level.
- Clay, which continues to hold its shape no matter what you do. Amend clay for better drainage.
For the next soil test, go back to your original hole and dig down a bit, until you’ve got a cavity about 12 inches deep by 6 inches wide. Fill this with water and allow to drain completely. Then refill the hole to the top. Keep track of how long the water takes to drain this second time; a period of more than 4 hours indicates a drainage problem.
Inadequate drainage will prevent air, water, and nutrients from penetrating the soil, and can cause topsoil to wash away when it rains.
How to Test Soil pH (Alkalinity)
This is the part you’ve been waiting for, if you like gadgetry. Here’s how to test soil pH:
- Purchase a soil test kit from your local garden center, containing test tubes, colored capsules, and a reference chart (AKA bells and whistles – whee!).
- Read the package insert, because the methodology varies with different brands.
- Thoroughly clean your trowel and put on gardening gloves (to avoid contamination of the soil sampling).
- Dig a 4-inch hole in a relatively dry area.
- Remove a small amount of dirt from the bottom.
- Discard any plant material or stones.
- Place the dirt in your handy-dandy pH test tube.
- Add the pH testing capsule and distilled water as per the package directions.
- Wait the specified amount of time until the mixture changes color.
- Compare the color to your reference chart, which runs from dark green (very alkaline) to bright red (very acid).
More modern (but not necessarily more accurate) ways of measuring soil pH include an electrically powered probe and a Wi-Fi connected “smart” gardening system.
Add manure or compost. This is an all-purpose fix for sandy soil, clay, and poor drainage. Mix in well-rotted manure or compost before planting, or topdress (sprinkle with a 1/4 to 1/2-inch layer) existing grass or other plants. Don’t overdo, though, especially the manure, or you’ll end up with new problems, such as an overdose of phosphorus, potassium, or salt.
Adjust pH. To lower pH, making the soil more acid, use pine needles or ground limestone. To increase pH, ground sulfur or gypsum is recommended. A level of 6-6.5 is usually desirable.
Aerate soil. Soil aeration is a mechanical means of improving drainage, which is frequently used on lawns. A device called a core aerator is rolled over the grass, removing small plugs of earth, which rest on the surface until they naturally disintegrate.
Install raised beds. If you have a serious drainage problem, raised bed or container gardening might be the solution. You’ll find it easy to achieve properly balanced soil in the relatively small space.
Consult an expert. A professional landscaper, who has experience working with many varieties of soil, can provide in-depth soil testing and expert advice on remedying your particular issue.
Laura Firszt writes for networx.com.
Updated December 20, 2018.
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