Soil Testing

square foot gardening Soil testNOTE: If you follow the square foot gardening method and use Mel’s Mix, I generally do not recommend testing your soil. It should be fine, and with a little added fertilizer you should have a plentiful harvest.

However, if your soil contains “dirt” or if you have had problems in the past and are looking for a solution, testing your soil could be a great benefit. I wrote this article in response to many such questions/problems–I decided to come up with some easy solutions, starting with soil testing.

If you want a professional, thorough soil test done, find your local extension office and contact them. I thought it was free, but it really costs about $50 to have soil tested in my area. I hoped there might be a cheaper options, and there is! I found this at my local IFA store for $9:

square foot gardening soil test kitContents:

  • 4 test tubes with lids
  • 4 capsules
  • Color chart
  • Instructions

Gather soil sample

I went out to my garden beds that I have prepared for the season and scooped some soil from each of 3 beds. I made sure to get soil that is about 4″ deep. I only needed about 1/4 cup, so I mixed the three samples and dumped most of it back.

square foot gardening soil

Testing pH

The first test (green) was for pH. The steps for this were slightly different. First, I put a small amount of soil into the green test tube up to the lowest mark.

square foot gardening soil test PHNext I opened up the green capsule and dumped the powder into the tube. As you can see, I made a mess of things.

square foot gardening soil test Ph powderNext I added water up to the top line.

square foot gardening soil test ph waterThen I put the cap on, mixed it up, and let it settle while the color developed. The instructions said this would take a minute, but I think it took more like 5 minutes.

square foot gardening soil test results PhAnd here are the results. To get an accurate reading, you really need to hold the tube up to natural light (not direct sunshine). It was an overcast day, so I just held mine up and looked through it by the window. From this picture the color looks much darker, but held up to the window the reading was more Alkaline/Normal.

Testing Nitrogen, Phosphorus, and Potassium (N-P-K)

Instead of putting soil directly in the tube, the instructions said to mix 1 part soil and 5 parts water, stir for one minute, then let it settle for 10 minutes.

square foot gardening soil test mixNext, put some water into each tube to the top mark. I used a turkey baster for this–since you want to avoid stirring up the sediment.

square foot gardening soil test tubesNext I opened the capsules and put one in each tube, replaced the lids, and shook them up well.

square foot gardening soil test tubes mixedThe instructions said to let them sit at least 10 minutes, and allow the color to develop and the sediment to settle. Here are the final results!

square foot gardening soil test resultsNow I just had to compare the color of the liquid to the color on the chart. Here are my results:

pH–normal, maybe slightly alkaline
Nitrogen–between medium and low
Phosphorus–low
Potash (Potassium)–very low

Conclusions

My first conclusion is that my garden will benefit from fertilizer.

I use Ferti-lome Blooming & Rooting Soluble Plant Food (9-59-8) on all my flowering vegetables (tomatoes, peppers, green beans, peas, zucchini, etc).

This year I am trying a mix of 16-16-8 plus Ironite applied in the spring. I also want to try some home brewed mixes and organic fertilizers.

Second, I am thrilled to find a less expensive option for testing my soil. My kit cost $9 and only included one test. Instead, I suggest buying the Luster Leaf 1601 Rapitest Soil Test Kit. Not only does it include 40 tests (10 for each), but I like that the color chart is printed right on the tube, so you can hold it up to the light and get a really good match. square foot gardening It costs $9.85–a MUCH better deal!

square foot gardening Soil Test

As I read reviews about soil tests it’s clear that these will not be as accurate and reliable as sending in a soil sample and paying $50, but I think it’s a great alternative at a reasonable price.

Also keep in mind that these don’t test for trace elements like boron, calcium, zinc, or iron. I suggest finding ways to supplement your garden with these nutrients as well.

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9 Responses

  1. Steve says:

    You can actually get lab soil tests done for pretty cheap, around 20 dollars. That will cover both the macro and micro nutrients. If you eat a lot of food grown yourself it certainly is a worthwhile investment.

  2. Emily says:

    Donna–yes, Mel’s book says you don’t need fertilizer, but I have not had a lot of success without it. I don’t know if any Texas read my blog, but maybe someone will contact you.

  3. Donna M. Bentkowski says:

    Emily, In Mels New Sq. FT. Gardening Bk . he says you don’t have to add fertilizer, why is that? Maybe it is because he recommends u use 5 different types of compost ?,do you do that?Luv that u r so thorough in your explanations. Your site ?blog?newsletters?e-mails Etc. R awesome.Thank u so much for all that u do. God Bless u.
    O another ?, Do u know of anyone from Tx.that is doing a sq. ft. garden ,specifically that lives near San Antonio, I live just 30 min. North of their in A town called Bulverde. It is part of the Hill Country.I would luv to talk to other people from my area about sq. ft. gardening, if u could please pass this message on i would appreciate it.My colors I believe r white and Olive.They could contact me by e-mail @bentkowskid@me.com.Thanks
    Donna
    Donna

  4. Aaliyah says:

    read everything before starting.

  5. Emily says:

    Cheryl–I’ve added a little explanation at the top now–generally you don’t have to test your soil. Add a variety of compost every year to your garden, I suggest boosting it with fertilizer, and you should be good to go. But if you’ve had problems and are troubleshooting, start with testing the soil. It’s cheap, easy, and gives you a baseline.

  6. shawn says:

    Just an FYI, the best time to test your soil is in the fall. That way, if you need to add lime or gypsum/sulphur, they have time to work. Lime can take 2-4 months and adding gypsum can take as long or more. Espoma has lime/gypsum products. Here is a link –>http://espoma.com/p_consumer/org_trad_overview.html

  7. Cheryl says:

    I’m new to square-foot gardening, so I have a question. Isn’t one of the benefits of SFG not having to test the soil?

  8. Emily says:

    Mary–it probably is best to take one sample from each garden bed. I only had one test, so I wanted to get an idea of all the soil. The kit I listed at the end of the article comes with supplies for multiple tests.

  9. Mary says:

    It is my understanding that you shouldn’t mix your soil samples if they are taken from different areas/gardens as the results are more specific to the soil from a specific garden. For example if you have a vegetable garden and a flower garden, or several separate raised beds, the soil may test different in each area/bed and you may need different nutrients in each bed.