How to Test Your Soil
1 of 6 in Series: The Essentials of Garden Soil
To have a successful garden, test your soil and amend it if necessary to create the best possible growing environment for plants. Testing your soil means you determine the pH level and nutrient content. Both are important factors in how well your garden grows.
Importance of pH levels and nutrients
Too much of this nutrient or too little of that, and you have problems. Just as humans need the right balance of nutrients for good health, so do plants. For example, when tomatoes grow in soil that’s deficient in calcium; they develop blossom-end rot. Sometimes, too much of a nutrient is detrimental: Excessive nitrogen causes lots of leaf growth (such as clematis or peppers) but few flowers or fruits.
The right pH enables plants to use nutrients from the soil. Soil is rated on a pH scale, with a pH of 1 being most acidic and a pH of 14 being most alkaline. If your soil's pH isn't within a suitable range, plants can't take up nutrients — like phosphorus and potassium — even if they're present in the soil in high amounts. On the other hand, if the pH is too low, the solubility of certain minerals, such as manganese, may increase to toxic levels.
Most vegetables and ornamentals grow well in a slightly acidic soil with a pH between 6 and 7.
The only way to find out whether your soil will be to your plant's liking is to test it. Don't worry; analyzing your soil isn't complicated, and you don't need a lab coat. Here are two ways that you can test your soil:
Use a do-it-yourself kit: This basic pH test measures your soil's acidity and alkalinity and sometimes major nutrient content. Buy a kit at a nursery, follow the instructions, and voilà — you know your soil's pH. However, the test gives you only a rough picture of the pH and nutrient levels in your soil. You may want to know more about your soil.
Have a soil lab do a test for you: A complete soil test is a good investment because a soil lab can thoroughly analyze your soil.
Here's what you can find out from a soil lab's test in addition to the pH level:
Your soil's nutrient content: If you know your soil's nutrient content, you can determine how much and what kind of fertilizer to use. In fact, many soil tests tell you exactly how much fertilizer to add.
Soil problems that are specific to your geographic region: A soil test may help you identify local problems. The soil lab should then give you a recommendation for a type and amount of fertilizer to add to your soil. For example, in dry-summer areas, you may have salty soil; the remedy is to add gypsum, a readily available mineral soil additive.
Fall is a good time to test soil because labs aren't as busy. It's also a good time to add many amendments (materials that improve your soil's fertility and workability) to your soil because they break down slowly.
To prepare a soil sample to use with a do-it-yourself kit or to send to a soil lab, follow these steps:
Fill a cup with soil from the top 4 to 6 inches of soil from your vegetable garden, and then place the soil in a plastic bag.
Dig six to eight similar samples from different parts of your plot.
Mix all the cups of soil together; place two cups of the combined soil in a plastic bag — that's your soil sample.
After you've collected your sample, consult the instructions from your soil test kit or the testing lab.