Grow Guides · April 28, 2026
Talking to a Soil Test Like It's Your Doctor
What each number means and what to do about it
Talking to a Soil Test Like It's Your Doctor
You get your soil test results back from USU Analytical Laboratories. Pages of numbers. Abbreviations. Ranges. It's confusing. But it doesn't have to be. A soil test is a diagnosis. Learn to read it and you know exactly what your soil needs.
The Big Three: pH, Organic Matter, Conductivity
pH is the foundation.
Most vegetables want pH 6.5–7.0. Blueberries want 4.5–5.5. If your Utah soil is 8.2 (it probably is), plants can't access nutrients even if they're present. pH is a lock. Nutrients are behind a locked door.
The fix: sulfur. 1 pound per 100 square feet lowers pH by 0.5–1.0 point in one year. Check our guide to amending alkaline soil.
Organic matter (OM) is the second foundation.
Healthy soil is 3–5% organic matter. Most Utah soil is less than 2%. OM holds water, feeds microbes, improves structure. Add compost. A lot of it. 3–4 inches worked in annually.
Conductivity measures salt concentration.
High conductivity (above 2.0) means excess salts. In Utah, this comes from hard water, alkaline minerals, or residual fertilizer. Plants stressed by high salts show stunted growth, leaf scorch, wilting even with water. Fix: leach the soil with deep watering, or add organic matter to buffer salts.
The Secondary Tests: Nitrogen, Phosphorus, Potassium
The N-P-K numbers tell you nutrient status. But be careful here—the test measures "available" nutrients, not total nutrients.
Nitrogen (N): results show ppm (parts per million). "Low" is below 20 ppm. "Adequate" is 20–50 ppm. "High" is above 50 ppm.
If you're low, add compost, aged manure, or a balanced fertilizer. If you're high, you're over-fertilized. Stop adding N and let the soil use it down over a season.
Phosphorus (P): This one is weird in Utah. Most Utah soils test high in P because of legacy irrigation water and dust. You probably don't need to add more. Adding excess P locks up micronutrients. Leave it alone unless the test says "very low."
Potassium (K): "Low" is below 100 ppm. Add potassium sulfate ("K-Mag") or wood ash. Potassium is critical for fruit quality and disease resistance.
Utah soils are naturally high in many mineral nutrients. Your bottleneck is usually pH, not nutrient availability. Fix pH first.
Utah State University Analytical Labs - Soil Test Interpretation — Dr. Larry Rupp (2024)
The Trace Elements (Iron, Manganese, Zinc, Copper, Boron)
These are micronutrients. Plants need them in tiny amounts. If your pH is high, these nutrients are locked up. Fixing pH usually fixes trace element deficiencies.
If the test shows deficiency and pH is already correct, add chelated micronutrient spray or compost-based amendments.
Calcium and Magnesium
Usually high in Utah. You don't need to add these. But if testing shows low levels and you're having blossom-end rot on tomatoes (calcium deficiency symptom), it's not usually a calcium shortage—it's inconsistent watering. Fix watering, not soil.
What a Typical Utah Soil Test Looks Like
pH: 7.8 (too high for vegetables; add sulfur)
OM: 1.5% (too low; add compost)
Conductivity: 1.4 (acceptable)
N: 35 ppm (adequate)
P: 88 ppm (very high; don't add more)
K: 140 ppm (adequate)
Your action plan:
1. Apply 2 pounds sulfur per 100 sq ft.
2. Add 3–4 inches compost, worked in.
3. Don't fertilize. Soil has plenty of P and adequate N/K.
4. Retest in 6 months. pH should drop 0.5–1.0 point.
Your soil is trying to tell you something. A soil test is just the translation.
