advertisement

This is the best time of year to get soil test results

Q. Why is fall the best time to do a soil test?

A. Those big bright roses, marvelous peonies and good-looking tomatoes in your neighbor's yard are likely the result of healthy soil that supplies the nutrients (especially nitrogen, potassium and phosphorus) and has the proper acidity, or pH level, to support such vegetation. And the best way to determine your soil's health is with a soil test done during the fall with soil you provide from your garden.

Why is autumn the ideal time to test? Here are four important reasons:

• Your soil has been at least somewhat depleted of nutrients after having sustained your plants through the spring and summer seasons.

• If the pH level needs adjustment with lime, fall is the best time to correct this condition (soil that is too acidic will not allow plants to uptake vital soil nutrients).

• Fertilizer (which supplies nitrogen, potassium and phosphorus and often "micronutrients" such as magnesium) is usually cheaper in the fall.

• Labs are generally less busy in the fall when fewer people approach them (spring is their busiest season).

Getting the soil from your garden involves removing dry soil with a soil probe. A spade or shovel will also work. You will need to dig below both the surface soil and mulch because you will want to analyze the soil at the level of the roots of the plants in the area you want tested. A depth of 3 to 5 inches is fine for lawn areas, but a 6- to 7-inch depth is necessary for borders where plants have larger root systems.

Take samples from several areas in the bed or lawn area so you get representative samples, allowing the lab to give you the best results.

Testing can be done at home, and home kits are available, but the most reliable tests are best done by a reputable and professional soil testing lab. Find a list of these at extension.illinois.edu/soiltest/, a website of the University of Illinois Extension Service. A lab identified with an "H" indicates it accepts home samples and one with an "I" means it provides interpretations for home samples.

If you plan on planting vegetables or other edibles, look for labs with the letter "M" showing which labs will test for heavy metals, such as lead and arsenic. If found, these soils should not be used for crops; use a raised bed with uncontaminated soil instead.

- Arlene Swartzman

• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 Monday, Wednesday and Saturday or (847) 201-4176, ext. 14, on Fridays. Visit web.extension.illinois.edu/mg.

Article Comments
Guidelines: Keep it civil and on topic; no profanity, vulgarity, slurs or personal attacks. People who harass others or joke about tragedies will be blocked. If a comment violates these standards or our terms of service, click the "flag" link in the lower-right corner of the comment box. To find our more, read our FAQ.