Compost Soil Test Results

Hey everyone, I got the compost tested so we knew what kind of nutrients it had and could plan out any adjustments that might be needed. When reading labels on products, most have instructions on what to do for 100 square feet. Our large plots are 20 x 6 feet, so 120 square feet.

I calculated all suggested amounts below assuming that your plot is 1/3 of the new compost and 2/3 of original soil.

pH could to be lowered a bit (more acidic)

The pH of the compost tested at 8.9. Tomatoes (and other veggies) ideal range is between 6.3 and 7.1. The soil regularly found in our plots tested at 6.7, so that is spot on. When mixed together that’s about 7.4. If you added a lot of compost, you might want to apply 6 lbs of sulfur (at 30% concentration) to your plot.  I used 1 bag of this product, which is in stock at the San Carlos Home Depot. It’s also available at Amazon. Note that 6 lbs should lower your pH by about 0.5 points, which is just perfect. See product directions here.

Add a little Calcium and Nitrogen

The Calcium and Nitrogen tested well. However, the Potassium is very high (see next section), so the soil test results suggest adding Calcium and Nitrogen to even out the ratio. Adding about 2 lbs of Calcium (gypsum) and 1-2 lbs of Nitrogen (14-0-0) should be sufficient.

Calcium: I bought a 40 lb bag of gypsum at Home Depot for $6 (it was all they had). It’s in the new ‘tool chest’ that showed up over winter. The combo for the lock is the same as the gates. Please use it, because I sure don’t need all 40 lbs!

Nitrogen: I used a bag of Blood Meal from Home Depot that was 12-0-0 NPK. (see the section below, you do NOT want a fertilizer with Potassium (K)).

Potassium is very high, do not fertilize with ANY Potassium this year

The potassium in the compost is about 5x higher than normal. So if you use any fertilizer, make sure there is no Potassium in it. Remember that the K in NPK stands for Potassium. So a 10-10-10 fertilizer for example has potassium.

When Potassium is high, it can inhibit the uptake of other nutrients, which is why the soil testing facility advised increasing the levels of Calcium and Nitrogen just a little to even out the ratios.

Garden Fundraiser:

I’d like to raise money for garden uses (and cover some of the costs I have made when buying extra shovels, etc). I’m raising a bunch of really fun organic heirloom tomato seedlings right now. If you’re interested in the seedlings either leave a comment or send me an email. I’d love it if you bought them from me instead of Home Depot (I’ll offer them for the same price as Home Depot). This way, the money goes back into the garden! Let me know how the following:

  • Number of tomato plants (so I can ballpark how many seedlings to keep around)
  • What kind (cherry, beefsteak, sauce tomatoes, etc)
  • If you’d like Herbs, summer squash, or anything else. I have a lot of seedlings, just let me know.

Lastly, if you shop on Amazon, please click this link first. I set up an affiliate account so we can collect a small percentage of sales to put back into the garden :) $1 here and $1 there helps, and costs none of us extra money!

  • Rusty Hopewell

    Hi Veronica
    First, thanks for the great job you’ve done with this site. Every time I remember to visit it I find more and more to read.

    Second, I’d love to get some of your heirloom tomatoes. I currently manage three gardens so I could use 6 cherries, 6 beefsteaks, and 12 sauce tomatoes. Do you need help transplanting into bigger containers? My 4H garden group is meeting this Sunday and could lend a hand.

    Third, do I owe you for the compost? I recall there being a cost, but then it just showed up one day and we all started helping ourselves.

    Finally, anything I can do to help with fundraising?


    • zoopercat

      Rusty, I just saw this post. The compost is $35. Also, my tomato seedlings are finally starting to get a bit beefier. Since you manage several gardens, I can give you any spares I have. And if you just want to make a donation, I don’t want to charge you the full $5 for each of them since that would be pretty expensive.

      The seedlings are small, about 2 inches tall with 2 sets of true leaves. I’d like to let them grow at least 2 more weeks before transplanting, if that’s ok with you.