Soil Test Analysis for the Backyard Veggie Garden

March 12, 2010

Annie Spiegelman author of “Talking Dirt,” “Growing Seasons,” and “Annie’s Garden Journal” is back again today to pick up the conversation on soil testing in the backyard garden right where we left off yesterday:

With the home soil test, you’ll be testing your soil’s pH. The pH level will tell you if your soil has the proper level for nutrient uptake or if you’re just out there over-fertilizing, polluting and wasting your hard earned cash on garden products.

“The ideal pH is 6.5. The reason we want it to be slightly acidic is because the plant nutrients are carried in a solution. If it’s slightly acidic, the nutrients can dissolve and can be transported,” says Andrews.

Determining and Adjusting for Proper pH in the Garden

Annie Spiegelman 300x199 Soil Test Analysis for the Backyard Veggie Garden“If the pH is too alkaline, the nutrients will sit there like lead balls of pasta, not going anywhere. By having it slightly acidic you have the best pH for nutrient uptake. To lower the pH, use coffee grounds, teabags or sulfur or aged animal manure.

To raise the pH, add Limestone or oyster or egg shells.” Being a compost groupie, I like to add a thin layer of compost on top of any soil amendments, as well. Compost slowly adds nutrients while also aiding in drainage and aeration.

Other Elements and Nutrients to Consider in a Soil Test

You’ll also be testing for the availability of your soil’s macronutrients; nitrogen (N), phosphorus (P) and potassium (K). These are the main nutrients and minerals needed by your plants.

You’ll see the letters NPK on fertilizer containers. Once you know which nutrients are already hanging out in your soil, you won’t be wasting money on unnecessary products.

Collecting Soil Samples from the Backyard for Testing

When collecting your home soil sample, choose a few different sections of your yard. For instance, your edible garden in raised beds would be one test area while your front lawn or a slope or a woody area would each be a separate area to test.

Annies Organic Garden 300x199 Soil Test Analysis for the Backyard Veggie Garden“For each chosen area, do a representative sampling. Pick ten to fifteen different spots in that area and dig down 6-8 inches,” recommends Andrews. “Remove critters, rocks, roots and plant material. You just want soil parts.

Take all samples from that area and mix them into a plastic baggie. Label the bag and the area accordingly. For a lawn, dig down only 2-3 inches. God help you if you’re growing a lawn in droughty California!”

Choosing the Specific Components of Your Soil Test

If you’ve decided to do the commercial test, you’ll be mailing in your sample to the company. Contact them and decide just how comprehensive a test you’d like to do. Andrews suggests testing for pH nutrient availability, particle size analysis, bulk density, moisture content, organic matter content, macro and micro nutrients and soluble salts (salts are soil killers!).

If you live in an urban area and are growing edibles or in an older home where lead contamination has been commonly found from paint, heavy metals testing should be done as well.

How Often Should You Test the Soil in Your Garden?

Commercial soil testing should be done when you first move into a home or every ten years or so, depending on your budget and your gardening success or utter failure.

The home soil test would be useful to do any time a considerable amount of plants in your yard look beaten down, chewed up, stagnant or like they’ve been smoking too much crack. Do a soil test (and tell them to make new friends).

Testing your soil twice a year; once in the spring and again in the fall, is especially helpful if you’re growing fruits and vegetables year round. “Cold season crops have different needs than warm season crops. Like us, our underground soil friends slow down when it’s colder outside,” says Andrews. “The bacteria slow down but once the soil warms up, the disco lights come on and they’re ready to party!”

Annie Spiegelman is a California Master Gardener and the garden columnist for the Bay Area’s Pacific Sun Talking Dirt Book Cover 218x300 Soil Test Analysis for the Backyard Veggie Gardennewspaper, where she writes the “Dirt Diva” organic gardening column. She is also a frequent contributor to Organic Style Magazine, New York Spirit, the Marin Independent Journal, Creative Home, Learn2Grow.com, and UrbanSustainableLiving.com.

She’s passionate about sustainable gardening and can often be heard lawn-bashing or talking dirt about the excessive use of chemical pesticides. Visit her website at www.dirtdiva.com (where critics will be composted).





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{ 4 comments… read them below or add one }

Delena Fredell March 28, 2010 at 5:41 pm

your gardening tips are really easy to implement. thanks for that. hope I will have enough time to take care of my garden in the future.

Brent Pohlman March 29, 2010 at 7:56 am

Great article on Soil Testing! Good Information!
Brent Pohlman – Midwest Laboratories

PlanterTomato April 18, 2010 at 9:38 am

I had my soil professionally tested earlier this year and would recommend that other gardeners do so as well. If you would like to see the report you get when using one of these services, I’ve posted a PDF of the report I got from Timberleaf Soil Testing on my web site (PlanterTomato.com). The URL for the specific posting on soil testing is: http://www.plantertomato.com/2010/04/professional-soil-testing.html

Jack June 6, 2011 at 5:52 am

P.H. is so important in the proper growth of vegaetables. Great post and lots of good information.

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