January Soil Test Field Day Follow Up
Soil Testing Field Day Follow-Up

This is a follow-up to our soil testing workshop on January 14, 2026.
Why test your soil?
Just to recap, there are a few reasons you should be regularly testing your soil:
- Adjusting and maintaining your soil pH at optimum levels for nutrient absorption
- Applying appropriate amounts of fertilizers
- Spotting "red flags" such as high salinity and identifying trends that could lead to problems
- Helping to diagnose crop issues
When to choose a private laboratory
I mentioned that soil tests from the University of Arkansas Cooperative Extension Service are free to Arkansas residents ($10 for out-of-state samples), but that there may be reasons to choose a private lab in certain situations.
- Private labs may have a faster turn-around for results
- May offer testing for compost, potting soils, or heavily amended soils
- May provide testing for heavy metals or soil contaminates
- May provide personalized consulting with a soil expert
In general, start with the free soil testing and consultation provided by Extension and utilize private labs for specialized testing or when diagnosing a crop issue requires an urgent analysis.
UA Soil Testing link: https://soil-testing.uada.edu/
UA Extension publications to check out
Extension offers a couple publications to help you understand the results of your soil test. While they are both very similar, it's worth reading both since they walk you through each section of the soil test and what the metrics mean.
Summary of the metrics
While there's general recommendations for what the ideal numbers are, it's important to research your individual crops in case their needs are different. Fortunately, the Extension soil test tailors its recommendations to the crops you indicated when you sent in your soil sample.
| Metric | Why It Matters | What to Target |
|---|---|---|
| Soil pH | Affects the ability of crop to uptake nutrients. | 6 - 7 is fine for most vegetables |
| Macronutrients | Provides the bulk of nutrients required by plants | Depends on the crop, Extension will provide optimum numbers |
| ECEC | Indicates the soil's ability to hold nutrients | Higher is better; Organic matter can improve this metric |
| Base Saturation | % of exchange sites occupied by Ca, Mg, K, and Na | >60% is ideal; Organic matter and raising pH will improve this metric |
| Sodium | High Na levels can reduce productivity | Avoid increasing Na % caused by build-up from fertilizers |
| Soil Texture | Affects soil's nutrient holding ability, pH buffering, moisture retention, and drainage | Difficult to change; Clay soils hold nutrients better than sandy soils and require more lime/sulfur to adjust pH |
Sodium (Na) levels are particularly worth watching for high tunnel growers, as they are more likely to see a continued build-up since rainfall isn't regularly flushing the soil.
Nutrient and fertilizer recommendations
Extension will take your results and do some math to calculate how much nutrients and lime (or sulfur) you need to add to your soil. These will be printed in a table toward the bottom of your results.
Keep in mind this table shows pounds of nutrients, not fertilizer, which is listed under the table in "Crop notes."
Adjusting results for your garden
If you're using conventional fertilizers, Extension will have listed a recommendation for you in the "Crop Notes" for each of the crops you indicated. All you need to do is adjust the recommendations to the size of your garden.
Nutrient recommendations are typically given in Lbs/Acre, Lbs/1000 Square Feet, or Lbs/100 Row Feet depending on the crop, although you can convert between them if necessary.
So to get the amount of fertilizer you need for your space, you just have to do a little math. Let's say your garden is 500 square feet.
If it's Lbs/1000 Square Feet:
500 / 1000 = 0.5
Now multiply the fertilizer or nutrient recommendations by 0.5 (half). If your results are in Lbs/Acre, use 43560 instead of 1000 in the above formula. If the results use 100 Row Feet, it will likely make more sense to just measure the length of your rows.
Keep in mind you don't need to fertilize paths and other non-growing areas in your garden. So subtract it from your total garden area and save some money on fertilizer.
What if you only use organic fertilizers?
What about the organic folks? Well, you have two options: either do the math yourself or ask an Extension agent to help you out. However, it's not too much more math to figure it out yourself.
Some things to note:
- Keep in mind that the NPK ratings on fertilizer bags indicate the percent by weight of Nitrogen, Phosphorus, and Potassium.
- Multiply the weight of the bag by the percent of the nutrient to find the amount (in pounds) of each nutrient.
- So, if your 100 lb bag has a rating of 8-4-3, then it contains 8 lbs Nitrogen, 4 pounds Phosphorus (P₂O₅), and 3 pounds of Potassium (K₂O)
- For liquid fertilizers you'll need to know the density in order to convert to volume
During the discussion, people asked about how to spread small amounts of fertilizer over a large area. While this is an unlikely issue, the easiest solution is to combine the fertilizer with a "bulking" agent like rice hulls, bio-char, compost, etc.
Looking forward and keeping records
Each soil test you receive is a single data point that gives you a snapshot of the condition of your soil. In order to be able to see the bigger picture, you need to be regularly soil testing and recording the results in order to spot trends.
- Record everything into a spreadsheet program like Excel, Google Sheets, or LibreCalc
- Keep a log that records events such as when you fertilize or apply lime
- Chart trends of soil metrics such as salinity (Na levels) or pH
- Cross-reference your soil test results and data with other records, such as harvest yields, to find patterns
Bottom Line
A soil test is a powerful diagnostic tool, but it’s only as useful as the actions you take afterward. By reading the key parameters, scaling the nutrient recommendations correctly, and keeping a disciplined record‑keeping habit, you’ll turn a single laboratory number into a sustainable, data‑driven gardening strategy.
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