Soil Test Interpretation Guide
| Element | Nitrogen (N-NO3) |
Phosphorus (P) | Potassium (K) | |||
Method |
2N KCl |
Bray |
Olsen |
Ammonium Acetate |
Ammonium Bicarbonate - DTPA |
|
| Rating/Units | ppm | ppm | ppm | meq/100g | ppm | ppm |
| Low | <20 | <20 | <10 | <0.45 | <175 | <60 |
| Adequate | 20-41 | 20-40 | 10-15 | 0.45-0.7 | 175-280 | 61-120 |
| High | 41-75 | 40-100 | 15-40 | 0.7-2.0 | 280-800 | 121-180 |
| Excessive | >75 | >100 | >40 | >2.0 | >800 | >180 |
| Element | Calcium (Ca) | Magnesium (Mg) | Sulfur (S-SO4) |
||
| Extraction Method |
Ammonium Acetate | Ammonium Acetate | KCL 40 | ||
| Rating/Units | meq/100g | ppm | meq/100g | ppm | ppm |
| Low | <5 | <1000 | <0.5 | <60 | <5 |
| Adequate | 5-10 | 1000-2000 | 0.5-1.5 | 60-180 | 5-10 |
| High | >10 | >2000 | >1.5 | >180 | 10-20 |
| Excessive | >20 | ||||
| Element | Iron (Fe) | Manganese (Mn) | Zinc (Zn) | Copper (Cu) | Boron (B) |
| Extraction Method |
DTPA | DTPA | DTPA | DTPA | Hot Water |
| Rating/Units | ppm | ppm | ppm | ppm | ppm |
| Low | <2.5 | <0.6 | <1.0 | <0.6 | <0.5 |
| Adequate | 2.5-5.0 | >2.0 | >1.5 | >2.0 | 0.5-2.0 |
| High | >5.0 | >2.0 |
| Interpretation of Soil Electrical Conductivity | ||
| Rating | 1:1 Extract EC (mmhos/cm) | Saturated Paste ECe (mmhos/cm) |
| Low (Non-saline) | 0.01-0.45 | 0.0-2.0 |
| Low (Slightly saline) | 0.45-1.5 | 2.1-4.0 |
| Medium (Moderately saline) | 1.51-2.9 | 4.01-8.0 |
| High (Strongly saline) | 2.91-8.5 | 8.01-16.0 |
| Very high (Very strongly saline) | >8.5 | >16.0 |
| Desirable range of exchangeable cations | |
| Cation | Range |
| Calcium | 65%-80% |
| Magnesium | 10%-20% |
| Potassium | 3%-8% |
| Sodium | <6% |
| Aluminium | <1% |
The values and ranges presented are in no way absolute. The aim is for you to use this document to get better understanding of the numbers and the terms used in soil test reports.
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