Soil Test Rating & Low, Medium or High
Rates nitrogen
Enter an available N, P or K value with the standard thresholds to classify it as low, medium or high— so you know whether to apply the full, reduced or maintenance dose.
Rate your soil test
Next: your N is in the medium band — apply a maintenance N dose to replace crop removal.
Bands are general critical limits; calibrated, region- and lab-specific thresholds should override these defaults for fertilizer recommendations.
Soil test rating — key facts
- Low
- below the low threshold
- Medium
- between the thresholds
- High
- above the high threshold
- Low → dose
- apply the full dose
- Medium → dose
- apply a reduced dose
- High → dose
- maintenance dose only
- Thresholds
- from your lab's method
- Privacy
- Runs in your browser; nothing uploaded
A number means nothing until it is rated
A soil test result is just a figure until you compare it against standard ranges. Labs class available nitrogen, phosphorus and potassium as low, medium or high, and that class — not the raw number — drives the decision. A low rating means the soil supplies little, so you feed the full dose; medium calls for a reduced dose; high needs only a maintenance dose because the soil already holds plenty.
This tool takes your value and the low and high thresholds for that nutrient and returns the rating, plus the thresholds it compared against, so you can interpret each result in seconds. Rate N, P and K separately, then size the actual fertiliser using crop-specific recommendations. Pair it with the Soil Test Crop Response, NPK and Nutrient Balance calculators to turn ratings into doses.
Read the lab report
Turn a number into low, medium or high.
Scale the dose
Full, reduced or maintenance feeding.
Avoid over-application
Skip wasteful dosing on high soils.
Rate each nutrient
N, P and K against their own ranges.
Frequently Asked Questions
What does a soil test rating do?+
A soil test returns a number — say available nitrogen, phosphorus or potassium per hectare — but a number alone does not tell you what to do. The rating classifies that value as low, medium or high against standard ranges, turning a lab figure into a decision: how much nutrient the soil can already supply and therefore how much you need to add.
How are the low, medium and high classes set?+
Each nutrient has a low threshold and a high threshold. A value below the low threshold is rated low, a value above the high threshold is rated high, and anything in between is medium. This calculator takes your value and those two thresholds and returns the class, along with the thresholds it compared against.
Why does the rating decide the fertiliser dose?+
A low rating means the soil supplies little of that nutrient, so you apply the full recommended dose; a medium rating calls for a reduced dose; and a high rating usually needs only a maintenance dose, or sometimes none, because the soil already holds plenty. Rating first prevents both under-feeding and wasteful, polluting over-application.
Where do the standard threshold values come from?+
Soil testing labs and agricultural universities publish rating ranges for each nutrient and extraction method in a given region. They differ by the test used (for example available N, Olsen or Bray P, ammonium-acetate K), so always use the thresholds that match your lab's method. Enter those into the tool for a correct class.
Can I rate N, P and K separately?+
Yes — and you should. Each nutrient has its own thresholds and can fall in a different class: a soil might be high in potassium but low in phosphorus. Rate each one against its own low and high thresholds and build the fertiliser plan nutrient by nutrient rather than treating the soil as a single grade.
Does a high rating mean I never fertilise?+
Not always. A high rating means the soil currently holds ample available nutrient, so a full dose is wasteful, but crops still remove nutrients at harvest. A maintenance dose replaces what the crop takes off to keep fertility from drifting down over seasons. Use the rating to scale the dose, not necessarily to skip it.
How often should I re-test and re-rate?+
Testing every one to three years tracks how fertility shifts with cropping and fertiliser use. Sample consistently — same depth, same season, well-mixed composite cores — so ratings are comparable over time. Re-rating after each test shows whether your dosing is building, holding or depleting each nutrient.
What units does it use?+
Enter the value and thresholds in the same units your lab reports (for example kg/ha for available N, P and K, or an index). The tool simply compares your value to the low and high thresholds, so as long as all three are in matching units the rating is correct. Pair it with the STCR and NPK calculators to set doses.
Is the rating definitive?+
It is a sound guide, but interpretation also depends on the crop, target yield, soil type and local calibration. Use the rating to place the value in low, medium or high, then refine the actual dose with crop-specific recommendations such as a soil-test crop-response equation.