Interpreting a Water Report: How to Make the Most of the Information You Have

So, before you sits a water quality report and you’re asking yourself, “now what?” It says you have a pH of 6.84 and an alkalinity of 37.3… is that good or bad? Well, read on my friends as we delve deeper into deciphering a water report.

What does pH Mean on a Water Report?

Potential of Hydrogen. This is the measure of the concentration of hydrogen ions (H+). pH is measured on a logarithmic scale of 1-14, with 1 being most acidic and 14 being most alkaline.

• Acceptable range is 6.5 to 8.0
• pH values under 6.0 and over 8.0 can cause severe problems
• pH influences the availability of plant nutrients and other elements.

What does Alkalinity Mean on a Water Report?

Think of this as the ability of water to neutralize acid. The higher the alkalinity, the more acid it will take to lower the pH of the water. Alkalinity is a measurement that incorporates the amount of bicarbonates, carbonates and hydroxides joined to calcium, magnesium and sodium. Alkalinity is expressed in parts per million (ppm) of Calcium Carbonate (CaCO3).

• Anything above 120 ppm CaCO3 could cause a gradual increase in the pH of your potting medium
• Low-alkalinity water (less than 60 ppm CaCO3) is not able to neutralize sufficient amounts of acid. As such, the recurrent use of acidic fertilizers might result in a decrease in the pH of your growing medium.

Electrical Conductivity (EC)

This is a measure of the conductivity of a solution. As the level of mineral salt dissolved in the water increases, so does the solution’s conductivity. Electrical conductivity is often expressed in reciprocal ohms (mhos). Most water reports express EC in millimhos per centimeter (mmhos/cm).

• Acceptable range is 0.5 to 0.75 mmhos/cm
• Problematic range is 0.76 to 3.0 mmhos/cm
• The severity of the problem will be determined by two factors: Which compound is responsible for the elevated EC and how high the EC is.

(For more on Electrical Conductivity, check out Electrical Conductivity and Monitoring Plant Nutrition)

Sodium Absorption Ratio (SAR)

This is a measure of the suitability of water for use in agricultural irrigation. It defines the sodium (Na) hazard by comparing the concentration of Na to the concentration of calcium (Ca) and magnesium (Mg). A high SAR value can cause reduced porosity in soils and create a salt crust on the surface, which will prevent water from being absorbed by the soil. Fine soils (i.e. clays) are affected more than large particle soils (i.e. sandy soils.)

• Acceptable range is less than 10 mEq/L(mEq/l is short for milliequivalents per liter)

• Problematic range is 10.1 – 18 mEq/L
• Severe problem range over 18 mEq/L

Phosphate

Commonly found in groundwater and fertilizers. Too many phosphates can cause algal blooms in runoff water, followed by significant decrease in dissolved oxygen. You can manage these levels with reverse osmosis filters or build fertilizer a program around the levels in your water supply

• Acceptable range is less than 1.2 ppm
• Problematic range is 1.2 to 2.4 ppm
• Severe problem range is over 2.4 ppm

Potassium

Potassium originates from dissolved rock, soil and fertilizer. High levels in the solution can increase K levels in plant tissue, thereby creating nutrient antagonism of N or Mg. You can also manage these levels with reverse osmosis filters

• Acceptable range is less than 20 ppm
• Problematic range is 20 to 50 ppm
• Severe problem range is over 50 ppm (can cause foliar damage)

Calcium

This originates from dissolved rock, limestone, gypsum, soil or fertilizer. High levels of Ca form lime deposits when combined with CO3 or HCO3.

• Acceptable range is less than 25 ppm for soil and water hazard, and less than 60 ppm for ideal foliar levels
• Problematic range is 25 to 250 ppm for soil and water hazard, and 60 to 100 ppm for problems with foliar injury
• Severe problem range is over 250 ppm for soil and water hazard, and over 100 ppm for severe foliar injury

Magnesium

Magnesium originates from dissolved rock, limestone, dolomite, soils, and fertilizers. High levels of Mg form lime deposits when combined with CO3 or HCO3.

• Acceptable range is less than 20 ppm
• Problematic range is 20 to 40 ppm
• Severe problem range is over 40 ppm

*Note: When designing a fertilizer program, remember the ideal ratio of K:Ca:Mg is 4:2:1

Zinc

Occurs naturally in small amounts.

• Acceptable range is less than 2.0 ppm
• Problematic range is greater than 2.0 ppm

Copper

Occurs naturally in small amounts, but Cu might be present due to corroding copper pipes.

• Acceptable range is less than 0.2 ppm
• Problematic range is 0.2 to 5.0 ppm
• Severe problem range is over 5.0 ppm; however, toxicity in some plants has been shown with levels as low as 1.0 ppm.

Manganese

Dissolved from shale and sandstone, and is not usually a problem.

• Acceptable range is less than 0.2 ppm
• Problematic range is greater than 0.2 ppm

Iron

Iron is the fourth most abundant element in the Earth’s crust. It’s not easily absorbed by plants unless the pH of the water is less than 5.5. Iron can mix with bacteria, causing slimes that can clog irrigation equipment.

• Acceptable range is less than 0.3 ppm
• Problematic range is 0.3 to 5.0 ppm
• Severe problem range is over 5.0 ppm
• Levels greater than 5.0 ppm can form coatings on leaf surfaces, reducing photosynthesis.

Sulfate

This is naturally dissolved into water from rock and soil containing gypsum, iron sulfides and other sulfur compounds. If mixed with calcium, scale can form. Reverse osmosis filtration is recommended course of action if levels are high.

• Acceptable range is under 100 ppm
• Problematic range is 100 to 200 ppm
• Severe problem range is greater than 200 ppm

Boron

Naturally occurring from ground water and decaying plant material. Boron is required in small amounts, but it is highly toxic when in excess.

• Acceptable range is less than 1 ppm
• Problematic range is 1.0 to 2.0 ppm
• Severe problem range is over 2.0 ppm

Sodium

Naturally occurring from dissolved minerals, but Na also comes from road salt and fertilizer. Levels greater than 70 ppm can cause foliar damage (leaf burn).

• Acceptable range is under 70 ppm
• Problematic range is 70 to 200 ppm
• Severe problem range is greater than 200 ppm

Chloride

Naturally occurs from dissolved minerals and sea water, but it also could come from road salt, fertilizer and sewage. Levels greater than 100 ppm can cause foliar damage (leaf burn). Chloride can be absorbed by plant roots accumulating in leaves causing toxicity.

• Acceptable range is under 70 ppm
• Problematic range is 70 to 300 ppm
• Severe problem range is over 300 ppm

Nitrate

Naturally occurring in soil and from decaying plant material, but high levels of nitrate is often the result of fertilizer usage. High concentrations can cause plant tissue to become more susceptible to pests.

• Acceptable range is less than 50 ppm
• Problematic range is 50 to 100 ppm
• Severe problem range is over 100 ppm