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Ca ++ Na +. Cl - SO 4 =. NO 3 -. Water Test Interpretation. Mike Kizer OSU Extension Irrigation Specialist. HCO 3 - CO 3 =. K + Mg ++. Measures of Water Quality. Electrical Conductivity (EC) Total Dissolved Solids (TDS) Individual mineral concentrations

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Water Test Interpretation

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Water Test Interpretation

Mike Kizer

OSU Extension Irrigation Specialist





measures of water quality
Measures of Water Quality
  • Electrical Conductivity (EC)
  • Total Dissolved Solids (TDS)
  • Individual mineral concentrations
  • Calculated salinity products (Hardness, SAR, Na%, etc.)
electrical conductivity ec
Electrical Conductivity(EC)
  • Pure water is a poor conductor of electricity
  • The more minerals dissolved in water, the more current it conducts
  • EC is a good estimator of total mineral content (TSS)
units ec
Units - EC
  • mmho/cm = (millimho per centimeter)
  • mmho/cm = (micromho per centimeter)
  • dS/m = (deciSiemen/meter)
  • mS/cm = (milliSiemen per centimeter)
  • 1 mmho/cm = 1 dS/m = 1mS/cm
  • 1 mmho/cm = 1000 mmho/cm
total dissolved solids tds
Total Dissolved Solids(TDS)
  • TDS is calculated by totaling all measured mineral concentrations as determined by chemical analyses
  • TSS is an estimate of TDS based on EC
  • EC (mmho/cm) x 640  TSS mg/l
  • This equivalence is approximate and depends on the ions causing the salinity
units tds tss
Units - TDS / TSS

mg/l = milligrams/liter ppm = parts per million

mg/l = micrograms/liter ppb = parts per billion

  • 1 mg/l = 1 ppm in water chemistry (1 liter of water weighs 1,000,000 mg)
  • 1 mg/l = 1000 mg /l
  • 1 mg /l = 1 ppb in water chemistry
sw fal water quality tests
SW&FAL Water Quality Tests

The OSU Soil Water & Forage Analytical Laboratory (Room 048 Ag. Hall) offers three water tests:

  • Livestock Water Test
  • Household Water Test
  • Irrigation Water Test

(All tests require a 1 pint water sample)

livestock water test
Livestock Water Test
  • Price: $6.00
  • Analytes:
      • pH
      • Total Soluble Salts (TSS)
      • Electrical Conductivity (EC)
      • Nitrate-Nitrogen (NO3-N)
livestock water quality total soluble salts tss
Livestock Water QualityTotal Soluble Salts -TSS

TSS (ppm)Interpretation

  • Less than 1000: Excellent
  • 1000 – 3000: Satisfactory for all animals
  • 3000 – 5000: Unsatisfactory for poultry
  • 5000 – 7000: Can be used except for pregnant, lactating or immature livestock
  • Over 10,000: Unsatisfactory for all animals
livestock water quality nitrate nitrogen no 3 n
Livestock Water QualityNitrate- Nitrogen –NO3-N

NO3-N (ppm)Interpretation

  • Less than 100: Satisfactory for all animals
  • 100 – 290: Use with care when given in combination with high nitrate feeds (especially certain forages in times of drought)
  • Over 290: Unsatisfactory for all animals
livestock water quality
Livestock Water Quality
  • Sulfate (SO4)
    • If most of the TSS are sulfates the acceptable TSS level is reduced because of scouring concerns
    • Polioencephalomalasia (PEM) is a nervous system disease in cattle caused by thiamine deficiency. High dietary sulfate has been linked to thiamine deficiency by research and case studies.
  • pH
    • The preferred range is 6.0-8.5. Animals can tolerate water outside this range, but some species may perform poorly.
household water test
Household Water Test
  • Price: $15.00
  • Analytes:
      • Sodium (Na)  Nitrate-Nitrogen (NO3-N
      • Calcium (Ca)  Iron (Fe)
      • Magnesium (Mg)  Manganese (Mn)
      • Potassium (K)  Zn
      • Boron (B) Electrical Conductivity (EC)
      • Hardness Total soluble Salts (TSS)
      • Chloride (Cl)  Sodium Percentage
      • Sulfate (SO4)  pH
household water test nitrate nitrogen no 3 n
Household Water TestNitrate-Nitrogen – (NO3-N)
  • NO3-N is the only analyte on the test with a Federal SDWA Standard
  • The NO3-N standard is 10 mg/l
  • Newborn infants (less than 9 months) and pregnant women are “at-risk” consumers
  • NO3-N affects the blood’s ability to carry oxygen, causing methemoglobenemia
household water test secondary contaminants
Household Water TestSecondary Contaminants
  • Other regulated analytes on the Household Water Test are Secondary Contaminants that have Federal SDWA Guidelines
  • Exceeding SDWA Guidelines is not a primary health risk
  • Secondary contaminants affect aesthetic quality of water (taste, odor, etc.) or damage the water system (hardness, corrosion, etc.)
household water test secondary contaminants16
Household Water TestSecondary Contaminants

Secondary contaminants can indirectly affect health:

  • High sulfates can cause diarrhea which could result in dehydration
  • Corrosion due to low pH and low alkalinity can leach lead and copper from plumbing fixtures which could cause lead toxicity
household water test hardness
Household Water TestHardness

Hardness is caused by calcium and magnesium (iron also contributes to hardness)

irrigation water test
Irrigation Water Test
  • Price: $15.00
  • Analytes:
    • Sodium (Na) —Chloride (Cl)
    • Calcium (Ca) —Sulfate (SO4)
    • Magnesium (Mg) —Nitrate-Nitrogen (NO3-N)
    • Potassium (K) —Carbonate (CO3)
    • Boron (B) —Bicarbonate (HCO3)
    • pH —Electrical Conductivity (EC)
    • Hardness —Total Soluble Salts (TSS)
    • Residual Carbonates —Sodium Adsorption Ratio (SAR)
irrigation water quality important analytes
Irrigation Water QualityImportant Analytes

•EC (or TSS): determines soil osmotic potential

•SAR (or Na%): rates infiltration problem potential

•Boron: toxic at very low concentrations

•Residual Carbonates (RSC): raises effective SAR/Na%


The Effect of Salinity of Soil Water Availability

Salt Concentrations

0.4% = 4000 mg/l

0.2% = 2000 mg/l

0.1% = 1000 mg/l

irrigation water quality sodium na hazard
Irrigation Water QualitySodium (Na) Hazard
  • Na generally creates soil infiltration problems before becoming toxic to plants
  • In hot, dry weather conditions sprinkling can lead to leaf burning due to Na toxicity
  • Na reduces soil permeability by dispersing clay particles which seal larger pore spaces
  • Na hazard is greater high clay content soils
  • Na hazard is greater in expanding clays than in non-expanding clays

Water Suitability Based on Total Salinity and Sodium Content

(Example: EC = 1.7 dS/m = 1700 mho/cm and Na%= 35)

irrigation water quality boron b
Irrigation Water QualityBoron (B)
  • Crops are very sensitive to boron
  • Threshold soil concentration for yield reduction: 0.3 – 5 mg/l
  • Toxic to all vegetation: 10-15 mg/l
  • Typical boron toxicity symptoms are spotting, yellowing and/or drying at tips and edges of older leaves
irrigation water quality residual carbonates rsc
Irrigation Water QualityResidual Carbonates (RSC)
  • Excessive bicarbonate and carbonate in irrigation water will combine with calcium and magnesium ions in soil
  • This effectively increases the SAR and leads to greater risk of infiltration problems
  • Residual carbonates ≥ 2.5 are usually a problem

RSC = (CO3 + HCO3) - (Ca + Mg)

nitrate nitrogen
Nitrate Nitrogen
  • NO3-N in irrigation water should be accounted for in nutrient management
  • 1 mg/L of NO3-N in irrigation water applies 0.23 lb/acre of N per 1 inch of irrigation water applied
water quality units and terms concentrations
Water Quality Units and Terms(Concentrations)

1 mg/l = 1 ppm = 1000 g/l= 1000ppb

TSS = Total Soluble Salts

TDS = Total Dissolved Solids


TSS, (mg/l)  640 x EC, (mmho/cm)

(Electrical Conductivity)

1 mmho/cm = 1 dS/m = 1 mS/cm= 1000 mho/cm

EC = electrical conductivity of water

ECe = electrical conductivity of saturated soil extract

water quality units and terms concentrations31
Water Quality Units and Terms(Concentrations)

meq/l = milliequivalents per liter

epm = equivalents per million

1 meq/l = 1 epm

Ionppm per meq/lIonppm per meq/l

Ca 20 CO3 30

Mg 12 HCO3 61

Na 23 SO4 48

K 39 Cl 35.5

derived water quality terms
Derived Water Quality Terms

SAR = Sodium Adsorption Ratio

SAR = Na (Ca+Mg)/2

Na% = Sodium Percentage

Na% = (Na x 100) (Ca+Mg+K+Na)

RSC = Residual Sodium Carbonates

RSC = (CO3 + HCO3) - (Ca + Mg)

(the 3 calculations on this page are in meq/l)

osu publications
OSU Publications
  • L-256 Understanding Your Livestock Water Test Report
  • L-296 Understanding Your Household Water Test Report
  • L-323 Understanding Your Irrigation Water Test Report
  • F-2401 Classification of Irrigation Water Quality

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