Soil pH to Nutrient Availability Converter
See how soil pH affects nutrient availability for plants.
Enter your soil pH to check which nutrients are optimally available and which may be locked out.
Enter your soil pH to see nutrient availability levels.
Understanding Soil pH and Nutrient Availability
Soil pH is a measure of acidity or alkalinity on a scale from 0 to 14. A pH of 7.0 is neutral. Values below 7 are acidic, and values above 7 are alkaline (basic). Most garden plants thrive in slightly acidic to neutral soil, typically between pH 6.0 and 7.0. The pH level directly controls which nutrients dissolve into the soil water and become available for plant roots to absorb.
The pH Scale and Soil:
The pH scale is logarithmic, meaning each whole number change represents a tenfold difference in acidity or alkalinity. Soil at pH 5.0 is ten times more acidic than soil at pH 6.0, and one hundred times more acidic than soil at pH 7.0. This is why even small pH adjustments can have a dramatic effect on nutrient availability.
Nutrient Availability by pH Range:
| Nutrient | Best Availability pH | Notes |
|---|---|---|
| Nitrogen (N) | 6.0 - 8.0 | Bacterial activity drops below 6.0 |
| Phosphorus (P) | 6.0 - 7.5 | Locks up in acidic and alkaline soils |
| Potassium (K) | 6.0 - 7.5 | Generally available in wide range |
| Calcium (Ca) | 6.5 - 8.5 | Deficient in very acidic soils |
| Magnesium (Mg) | 6.0 - 8.5 | Similar to calcium |
| Sulfur (S) | 6.0 - 8.0 | Widely available |
| Iron (Fe) | 4.0 - 6.5 | Locks up above pH 7.0 |
| Manganese (Mn) | 5.0 - 6.5 | Toxic at very low pH |
| Zinc (Zn) | 5.0 - 7.0 | Less available in alkaline soil |
| Copper (Cu) | 5.0 - 7.0 | Similar to zinc |
| Boron (B) | 5.0 - 7.0 | Leaches in acidic, locks in alkaline |
| Molybdenum (Mo) | 7.0 - 8.5 | Opposite of iron |
The Sweet Spot:
Most nutrients are simultaneously available between pH 6.0 and 7.0. This is why most gardening guides recommend maintaining soil in this range. At pH 6.5, nearly all essential nutrients are at or near peak availability. Blueberries, azaleas, and rhododendrons are notable exceptions that prefer acidic soil around pH 4.5-5.5.
Adjusting Soil pH:
- To lower pH (make more acidic): Add eleite sulfur, aluminum sulfate, or acidic organic matter like pine needles
- To raise pH (make more alkaline): Add agricultural lime (calcium carbonate) or wood ash
- Changes take weeks to months to fully take effect in the soil