Soil fertility is a confounding topic for new and experienced gardeners alike. Anyone asking an Extension agent what fertilizer to use has likely heard, “Get your soil tested to find out the right fertilizer for your garden.”
Soil testing is a simple way to learn about the soil’s chemistry. The test results provide customized fertilizer recommendations for the garden. For more information about soil testing, visit HGIC 1652, Soil Testing.
While soil testing is simple enough (you don’t even have to study for it), interpreting the results can be challenging. Hardly a week passes without the HGIC hearing, “I just got my soil test results back, and I don’t have a clue what I’m looking at!” It is understandable. Unfortunately, the soil test results aren’t user-friendly. Let’s try to simplify reading the results.
First, in the email from the Agricultural Service Laboratory, click on the link to go to the test results. The next page will look like this. (Figure 1)
After clicking on the link in the email to go to the soil test results, this page will appear.
So, the information on this page gives a lazy gardener (LG) anxiety. What do all these letters and numbers mean!? Don’t worry, breathe. I got choo, Boo.
Locate and click on the blue number under LabNum, in this case, 22051888. The lab number links to your soil report, the most valuable information to an LG. (Figure 2)
Starting near the top of the report, under Analysis and Results, find Soil pH. (Figure 3) Don’t get too hung up on Buffer pH. Buffer pH is a critical value for the lab in making lime recommendations. However, it is not something on which an LG needs to waste time.
Soil pH is vital to determining nutrient availability to plants. Most plants access nutrients at a slightly acidic pH of 6.0 to 6.5. Exceptions include azaleas, rhododendrons, and blueberries, which prefer an acidic soil pH between 5.0 to 5.5. Centipedegrass prefers 5.5 to 6.0. For more information about soil pH, visit HGIC 1650, Changing the pH of Your Soil.
Skip down the page to the Recommendations section. To the right of Recommendations, it says Lime. (Figure 4) The lime recommendation is just below and to the right of the word Lime. (Figure 5) It will either say ‘No lime required’ or provide lime recommendations in pounds per 1,000 square feet (lbs./1000 sq ft).
More critical information on the soil test result is in the Comments section under the specific crop. Specifically, the fertilizer recommendations are in the Comments section. (Figure 7)
While all the comments are informative and help explain the finer points of the soil test result, not all are created equal. Soil test newbies should read through all the comments. Some comments explain how to measure fertilizer without a scale. While others provide fertilization ranges or supplemental fertilizer for turfgrass or what to do when certain nutrients are high, or soil pH is at an extreme. (Figure 8)
Besides the lime recommendation, which an LG found earlier, the fertilizer recommendation is the other primary reason for soil testing. In this example, comment 426 provides the type and amount of fertilizer to apply and when. (Figure 9)
426. When growth begins in the spring, broadcast 3 lbs triple superphosphate (0-46-0) and 3 lbs 34-0-0 per 1,000 square feet. In July, broadcast 3 lbs 34-0-0 per 1,000 square feet.
Those with further questions about their soil test report can contact the HGIC for more information. Have the soil test report number and square footage of the area to be treated when calling.
Once an LG knows how much lime and fertilizer to put out, they have gotten their $6.00 worth and can get on with their gardening. After all, gardening is what it’s all about, right?