How to Read a Soil Test Report

Soil Health · February 2026 · 4 min read

A soil test is the foundation of smart farming. It tells you exactly what your soil has, what it needs, and how to avoid wasting money on unnecessary fertilizer. Here's how to read the key numbers on your report.

The Big Three: N-P-K

Every soil test measures the three primary macronutrients. They're reported in parts per million (ppm):

Nitrogen (N): Drives vegetative growth. Optimal range: 25–50 ppm. Below 25 = apply nitrogen fertilizer (urea, UAN). Nitrogen is mobile in soil and depletes quickly.
Phosphorus (P): Essential for root development and energy transfer. Optimal range: 15–40 ppm. Below 15 = apply MAP (11-52-0) or DAP (18-46-0).
Potassium (K): Regulates water use and disease resistance. Optimal range: 120–200 ppm. Below 120 = apply potash (0-0-60).

pH: The Gatekeeper

Soil pH controls nutrient availability. Even if you have plenty of N-P-K, plants can't access them if pH is wrong.

Below 5.5: Very acidic — apply agricultural lime. Many nutrients become locked up.
5.5–6.0: Slightly acidic — consider liming, especially for alfalfa and clover.
6.0–7.5: Optimal for most crops. This is the sweet spot.
7.5–8.5: Alkaline — micronutrient deficiencies (iron, zinc, manganese) become common.
Above 8.5: Very alkaline — apply elemental sulfur or gypsum to lower pH.

Organic Matter (OM%)

Organic matter improves water-holding capacity, nutrient cycling, and soil structure. Most Midwest farm soils range from 2–5%. Higher is generally better. Build OM with cover crops, reduced tillage, and manure applications.

CEC (Cation Exchange Capacity)

CEC measures your soil's ability to hold and release nutrients. It's like the "battery capacity" of your soil. Higher CEC means your soil can store more nutrients. Sandy soils have low CEC (5–10), clay soils have high CEC (20–40). CEC doesn't change easily — it's an inherent property of your soil type.

🧶 Plug your numbers into our free interpreter:

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How Often to Test

Test your soil every 2–3 years for each field, sampling at the same time of year for consistent results. Fall is ideal — it gives you time to plan amendments before spring planting. Always sample at a consistent depth (6–8 inches for row crops) and pull 15–20 cores per field, mixed into one composite sample.