Appendix

A. Meq/l equals mg/l divided by the equivalent weight where equivalent weight equals atomic weight divided by atomic charge. You will need to reference atomic weights and charges in Determining the Suitability of Salt-Affected Water and Soil for Tree and Shrub Plantings, Plant Materials Technical Note No. MT-62.

meq/l = mg/l (atomic weight ÷ atomic charge)

If we have 325 mg/l calcium and want to know the value in meq/l, 325 = 16.21 meq/l we use the formula: (40.1 ÷ 2)

B. You have an electrical conductivity reading of 855 mmhos/cm and want to compare this value to standards given in dS/m. Since mmhos/cm is equivalent to dS/m, the value stays the same (855 mmhos/cm x 1 = 855 dS/m.)

C. You have an electrical conductivity reading of 637 mmhos/cm and want to compare this value to standards given in µmhos/cm. To convert, multiply 637 mmhos/cm x 1,000 = 637,000 µmhos/cm. Conversely, if you have 637,000 µmhos/cm, divide 637,000 µmhos/cm by 1,000 to convert to 637 mmhos/cm.

D. You have an electrical conductivity reading of 769 S/m and want to compare this value to standards given in dS/m. To convert, multiply 769 S/m x 10 = 7,690 dS/m. Conversely, if you have 7,690 dS/m, divide 7,690 dS/m by 10 to convert to 769 S/m.

E. All readings in µS/cm are equal to readings in µmhos/cm, so 325 µS/cm equals 325 µmhos/cm.

The Analysis Examples are available for download in Adobe Reader format.

Analysis Example 1 - Results  (PDF; 17 KB)
Analysis Example 2 - Results  (PDF; 17 KB)

Analysis Example 1 – Interpretation

Texture. A soil texture classification of “Clay” suggests water infiltration into the soil, percolation of water through the soil profile, as well as soil aeration may be compromised. It will be difficult to use leaching as a soil salts management technique on soils with this texture. Incorporation of large volumes of sand and/or organic matter, in conjunction with the installation of drainage systems may be necessary. Select tree and shrub species tolerant of heavy-textured soils.

Conductivity. Based on standards in Table 1, soil with a conductivity reading of 4860 umhos/cm (4.86 dS/m) would have a soil salinity classification of “Slightly Saline”. Only non-sensitive trees and shrubs would grow to full performance at this salinity level without additional management. As noted earlier, the high clay content of this soil would make leaching of salts difficult. Other salinity tests should be evaluated to determine if additional management will be needed. Similarly, if soil salt leaching or other management is being considered, water quality tests should be conducted.

Sodium Adsorption Ratio. A soil with an SAR of 2.19 would not suggest any plant growth limitations based on the sodium level relative to other ions. A soil with an SAR of 2.19 and an EC of 4860 umhos/cm would result in a soil classification of “Saline”.

Calcium. A soil calcium level of 355 mg/l (ppm) does not indicate a soil quality problem. Calcium level alone is not typically an important soil quality parameter, but is used to calculate SAR.

Magnesium. A soil magnesium level of 121 mg/l (ppm) does not indicate a soil quality problem. Magnesium level alone is not typically an important soil quality parameter, but is used to calculate SAR.

Sodium. A soil sodium level of 188 mg/l (ppm) does not indicate a soil quality problem. Sodium level alone is not typically an important soil quality parameter, but is used to calculate SAR.

pH. Based on classifications in Table 2, a soil pH of 8.1 is considered “Moderately Alkaline”, but is still considered within the acceptable pH range for the growth of many trees and shrubs, with the exception of woody species that specifically prefer acidic soils. Acidifying fertilizers, as well as amendment with stable (chelated) forms of insoluble nutrients may be necessary for adequate growth of certain trees and shrubs.

Summary Interpretation. The total salinity level of this soil sample, although not exceptionally high, will limit its use to non-salt-sensitive tree and shrub species, unless additional management is provided. Only the soil texture and pH results suggest other potential limitations. If nutrient availability to plants is determined to be an issue because of the high soil pH, acidifying products should be added to the soil and/or irrigation water. Water filtration, such as reverse osmosis, may be helpful if irrigation water is the source of the soil salts, or if leaching will be attempted. A complete water analysis is recommended before proceeding with any corrective measures if there is a likelihood of high irrigation water salts.

Analysis Example 2 - Interpretation

Texture. A soil texture classification of “Loamy Sand” suggests that water infiltration, percolation, and soil aeration should not be limiting. Leaching of salts from the soil profile with excess irrigation water should be possible, given other favorable conditions.

Conductivity. Based on the standards in Table 1, soil with a conductivity reading of 855 umhos/cm (0.855 dS/m) would have a salinity classification of “Non-Saline”. Leaching or other management practices are not currently needed. Water quality tests should also be conducted if salts in irrigation water are a concern.

Sodium Adsorption Ratio. A soil with an SAR of 12.24 would not indicate plant growth limitations based on the sodium level relative to other ions. This is, however, close to the SAR level (~>13) at which water infiltration and soil aeration can become limiting. An SAR value of 12.24 in conjunction with an EC of 855 umhos/cm (0.855 dS/m) would result in a soil classification of “Normal”.

Calcium. A soil calcium level of 29 mg/l (ppm) does not indicate a soil quality problem. Calcium level alone is not typically an important soil quality parameter, but is used to calculate SAR.

Magnesium. A soil magnesium level of 20 mg/l (ppm) does not indicate a soil quality problem. Magnesium level alone is not typically an important soil quality parameter, but is used to calculate SAR.

Sodium. A soil sodium level of 355 mg/l (ppm) does not indicate a soil quality problem. Sodium level alone is not typically an important soil quality parameter, but is used to calculate SAR.

pH. Based on standards in Table 2, a soil pH of 8.8 is classified as “Strongly Alkaline” and would not be suitable for most trees and shrubs, with the exception of alkaline tolerant species. Regular applications of acidifying fertilizers, as well as amendment with stable (chelated) forms of insoluble nutrients will be necessary for adequate growth of most trees and shrubs. The 8.8 pH is only characteristic of soils classified as “Sodic” (see Chart 3 in Determining the Suitability of Salt-Affected Water and Soil for Tree and Shrub Plantings, Plant Materials Technical Note, MT-62.

Summary Interpretation. The SAR of this soil is close to a level that may impact tree and shrub survival and growth. Water filtration, such as reverse osmosis, may be necessary if additional sodium is added to the soil via irrigation water. Only the soil pH results suggest additional potential problems. If nutrient availability to plants is determined to be an issue because of the high soil pH, acidifying products should be added to the soil and/or water. A complete water analysis is recommended before proceeding with any corrective measures if there is a likelihood of high irrigation water salts.

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Last Modified: 08/21/2008