From: Bernardita Sallato, Extension Specialist, Agriculture and Natural Resources, Washington State University; Tianna DuPont, Extension Specialist, Agriculture and Natural Resources, Washington State University; David Granatstein, Sustainable Agriculture Specialist and Professor Emeritus, Washington State University. Revised December 2022. Download PDF EM119E
Table 1. Recommended soil test levels and testing methods for tree fruit. Source: Sallato et al.,2019
| Soil test | Unit | Low | Optimal | Excessive | Methoda |
|---|---|---|---|---|---|
| pH | – | < 5.0 | 6.0 – 7.5 | > 8.0 | 1:1 /CaCl |
| E.C paste | mmhos/cm | – | < 2.6 | > 4 | Paste |
| E.C 1:2.5 or 1:1 | mmhos/cm | – | < 0.5 | > 1 | 1:1 |
| P-Olsenb | ppm | < 10 | 15 – 40 | > 50 | NaHCO3 |
| Potassium (K) | ppm | < 120 | 150 – 250 | > 300 | NH4OAc |
| Potassium (K) | meq/100g | < 0.3 | 0.4 – 0.6 | > 0.7 | NH4OAc |
| Calcium (Ca) | meq/100g | < 3.0 | 4.1 – 20 | NH4OAc | |
| Magnesium (Mg) | meq/100g | < 0.5 | 0.5 – 2.5 | > 2.5 | NH4OAc |
| Sodium (Na) | meq/100g | < 0.5 | > 0.5 | NH4OAc | |
| Boron (B) | ppm | < 1.0 | 1.0 – 1.5 | > 1.5 | CaCl 0,01 mol/L |
| Sulfur (S)c | ppm | < 4 | 9 – 20 | > 20 | Ca3(PO4)2 |
| Zinc (Zn) | ppm | < 0.25 | 0.6 – 1.0 | DTPA | |
| Copper (Cu) | ppm | < 0.1 | 0.6 – 1.0 | > 20 | DTPA |
| Manganese (Mn) | ppm | 1 – 5 | > 50 | DTPA | |
| Iron (Fe)d | ppm | > 4.5 | – | – | DTPA |
| ppm | 0.11 – 0.20 | – | DTPA |
Note: mg/kg = ppm. ppm = meq/100g*MW/charge*10.
a Methods: Plant, Soil and Water Reference Methods for the Western Region. 2005. R. G. Gavlak, D. A. Horneck, and R. O. Miller.
b P-Olsen is recommended to mildly acid to alkaline soils of eastern Washington. Gavlak et al 2005.
c The method has a detection limit of 2.0 mg kg-1 (dry basis) and is generally reproducible to within ± 15%. Better to look at in tissue analysis.
d Soil analyses for Fe, does not correlate well with Fe availability.
