How to Read Your Soil Test Results (And What to Do About Them)

Why Soil Tests Matter (And Why Most Farmers Misread Them)

A soil test report is one of the most valuable documents in agriculture — and one of the most underused. Most farmers get a report, look at the pH number, and put the paper in a drawer. This guide will walk you through every major number on a standard soil test, explain what it actually means for your crop, and show you where biological inputs like AgZyme and Super Hume address the most common deficiencies.

Before interpreting your results, always note the lab that ran your test and the county extension service recommendations attached. Different labs use different extraction methods (Bray P1, Mehlich-3, Olsen) which produce different absolute numbers. Trends across multiple years from the same lab are more meaningful than a single snapshot.

pH: The Foundation of Everything Else

Soil pH is a measure of hydrogen ion activity in soil solution, running from 0 (most acidic) to 14 (most alkaline). For most row crops, the agronomically optimal range is 6.2–6.8. Here's why pH matters so much: it controls nutrient availability even when nutrients are physically present in the soil.

pH Range	Soil Type	Primary Concerns
Below 5.5	Highly acidic	Aluminum & manganese toxicity, phosphorus lockup, poor legume nodulation
5.5–6.1	Moderately acidic	Suboptimal P availability, reduced biological activity, lower yield potential
6.2–6.8	Optimal	Maximum nutrient availability across macro and micronutrients
6.9–7.4	Slightly alkaline	Iron, zinc, manganese availability begins to decline
Above 7.5	Highly alkaline	Severe micronutrient deficiency, phosphorus fixation, reduced biological activity

Biological implication: Biological products including enzyme complexes perform best in the 6.0–7.5 pH range. Below 5.5, the microbial community is suppressed and enzyme activity is significantly reduced. If your pH is below 6.0, lime application to correct pH should accompany any biological program.

Humic acid helps in high-pH soils: Super Hume and similar humic acid products chelate micronutrients in high-pH soils, making iron, zinc, and manganese more available to roots even when pH would otherwise lock them up. If correcting pH isn't immediately practical, humic acid additions are a meaningful partial solution.

Cation Exchange Capacity (CEC): Your Soil's Nutrient-Holding Bank Account

CEC measures your soil's ability to hold positively charged nutrient ions (cations) like calcium, magnesium, potassium, and ammonium. It is expressed in milliequivalents per 100 grams of soil (meq/100g) or centimoles per kilogram (cmol/kg) — these are numerically equivalent.

CEC Value	Soil Texture	Implication
Below 7	Sandy, coarse	Nutrients leach quickly; split applications essential; high humic acid benefit
7–15	Loamy	Moderate nutrient retention; balanced fertility programs work well
15–25	Clay loam, silt loam	Good nutrient retention; focus on cation balance and pH
Above 25	Heavy clay	High retention but potential tightness; aeration and biology are priorities

What to do about low CEC: Organic matter and humic acid are the primary tools for improving CEC in low-CEC soils. Humic acid additions from products like Super Hume provide immediate CEC improvement — humic molecules carry negative charges that directly increase exchange capacity. Long-term CEC building requires building organic matter through cover crops, reduced tillage, and biological programs that accelerate residue conversion to stable humus.

Phosphorus: The Most Frequently Mismanaged Nutrient

Soil test phosphorus (P) is typically reported as ppm or lb/acre of plant-available P. "Plant-available" is the critical qualifier — most soils contain hundreds of pounds of total phosphorus, but only a fraction is in forms roots can access. The percentage that's available depends heavily on soil pH, biological activity, and the presence of iron and calcium compounds that bind phosphorus.

Sufficiency ranges vary by crop, but for corn and soybeans the general guidance is:

• Below 15 ppm (Mehlich-3): Deficient — significant yield loss likely without supplemental P
• 15–30 ppm: Low — yield response likely; prioritize P applications
• 30–50 ppm: Optimal range for most Corn Belt row crops
• Above 50 ppm: High — minimize additional P inputs, focus on efficiency

Biological path to P efficiency: AgZyme and other enzyme products improve phosphorus availability by stimulating phosphatase enzyme activity in the soil, which converts organic phosphorus into plant-available inorganic forms. Humic acid chelates and stabilizes phosphorus, reducing fixation by iron and calcium. Operations with adequate soil P but poor efficiency may see more response from biological inputs than from additional fertilizer P.

Potassium: Often Misread Due to Sampling Variability

Soil potassium (K) is highly variable across fields, influenced by texture, sampling depth, and recent fertilizer application. Test results are typically reported as ppm or lb/acre of exchangeable K. General sufficiency levels for corn/soybeans run 120–160+ ppm depending on CEC and crop removal.

A low K reading in isolation doesn't always indicate deficiency — soil sampling errors (wrong depth, wet samples, too few cores) are common. If you have a low K reading but no visual symptoms and normal yield history, resample before responding with heavy K applications.

Note on Huma K: If you're addressing both low CEC and low potassium, Huma K — potassium humate — addresses both simultaneously, providing humic acid for CEC improvement alongside supplemental potassium.

Organic Matter: The Long-Term Indicator

Organic matter (OM) percentage is perhaps the most meaningful long-term indicator of soil health. Each 1% of organic matter in the top foot of soil holds approximately 1,000 lbs of nitrogen in organic form, represents significant water-holding capacity improvement, and supports a thriving microbial community.

OM %	Assessment	Priority Action
Below 1.5%	Severely depleted	Cover crops, reduced tillage, biological program immediately
1.5–2.5%	Below average	Active building program; biologicals as catalysts
2.5–4.0%	Adequate to good	Maintain and improve; biologicals unlock existing OM
Above 4.0%	Excellent	Protect — maximize biological activity to convert OM to available nutrients

Biological inputs directly address organic matter utilization: AgZyme accelerates the breakdown of crop residue and existing organic matter into available nutrients. This doesn't reduce OM — it improves the ratio of active (plant-available) to passive (locked) organic matter fractions. Over multiple seasons, the improved microbial environment from biological programs consistently supports OM building rather than depletion.

Building Your Response Program

After interpreting your soil test, prioritize your response actions:

1. pH correction first — lime if below 6.0. Nothing else performs well in highly acidic soils.
2. Address severe P or K deficiencies — these are yield-limiting and require direct supplementation.
3. Add biological inputs to improve efficiency — AgZyme for nutrient cycling and enzyme activity, Super Hume for CEC and micronutrient chelation, Huma K if both CEC and K are low.
4. Plan for organic matter building — cover crops, residue management, and biological programs work together over multiple seasons.

Re-test every 2–3 years on the same fields at the same time of year, using the same lab. Year-over-year trends matter far more than any single test result. Operations running consistent biological programs typically see measurable OM improvement by year 3–4, with corresponding improvements in nutrient efficiency and yield stability.