IRRIGATION WATER QUALITY

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IRRIGATION WATER QUALITY

• James J. Camberato
• Clemson University

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Water Quality Concerns

• Alkalinity -- pH, carbonates
• Sodium
• Salinity
• Specific ions -- Cl, B, Fe

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Alkaline water

• High pH and carbonates
• pH gt 7.0
• carbonates gt 2.0 meq/l or 120 ppm
• Residual sodium carbonate gt 1.25

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Problems with alkaline water

• Carbonates and high pH cause precipitation of
  calcium carbonate
• sodium dominates soil
• pH gt 7
• micronutrient availability reduced
• foliar residues also occur

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Bicarbonate problems in SC
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Deep well sample -- Charleston
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Residual Sodium Carbonate Equation

• RSC (CO32- HCO3-)
• (Ca2 Mg2) in meq/l
• When RSC greater than 1.25 problems may occur

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Create Acidity

• Acidic fertilizers
• Elemental sulfur
• Sulfur dioxide injection/water
• Sulfuric acid injection/water

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Reaction of common materials
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Careful with Elemental Sulfur
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Ammonium sulfate

• 5 lb amm. sulfate per 1000 sq. ft. generates
  enough acidity to neutralize approximately 22
  inches of irrigation water containing bicarbonate
  at 2 meq/l or 120 mg/l

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N sources effect soil pH
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Spray tank pH important to half-life of pesticides
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Half-life of carbaryl -- pH effects
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Insecticides affected by pH

• Diazinon
• Disulfoton
• Carbofuran
• Guthion
• Fluvalinate
• Methamidophos

• Acephate
• Parathion
• Chlorpyrifos methyl
• Carbaryl
• Oxamyl
• (Gorsuch and Griffin)

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Overcoming High Alkalinity

• Dont over water
• Acidic fertilizers/amendments
• Acidify irrigation water
• Residue - irrigate in eve., less frequent
• Use buffer in spray tank

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Sodium

• Sodium adsorption ratio -- sodium versus calcium
  and magnesium
• SAR gt 10 problem in soil
• Sodium gt 70 ppm
• disrupts soil structure
• direct toxicity

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Sodium adsorption ratio

• Ratio of sodium to calcium and magnesium
• Salinity of water should also be considered
• sodium has greater effect at low salinity than
  high salinity

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Sodium and Salinity Determine Water Infiltration
Properties
Good Water Infiltration
Poor Water Infiltration
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Deep well sample -- Horry
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Recycling pond - Charleston
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Overcoming high SAR

• Leach soil when possible
• Apply soluble calcium
• Correct alkalinity problem

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Typical problem in coastal SC

• Water high in bicarbonate and sodium
• Calcium carbonate forms in soil
• Sodium dominates cation exchange sites

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Disruption of soil structure

• Dispersion of fines and organic matter occurs
• Soil pores become blocked
• Water infiltration is reduced

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Other irrigation water quality problems
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Salinity

• Electrical conductivity -- EC or Total dissolved
  salts -- TDS
• EC gt 2.0 mmhos/cm or TDSgt1,280 ppm TDS
• tissue burn, drought stress

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Salinity problems evident with extended drought

• one-inch of water with salinity of 1.0 dS/m adds
  3.3 pounds of salt per 1000
• 1 to 2 inches of water used weekly during peak
  demand
• compare to typical fertilization where total salt
  is generally less than 2 pounds per 1000

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Overcoming high salinity

• Dont under water
• Leach soil when needed
• Use slow-release fertilizers
• Dilute poor water with good water

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Specific ion toxicity

• Boron -- B
• Chloride -- Cl

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Deep well -- Charleston
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Ornamentals sensitive to boron

• Cherry
• Elm
• Pansy
• Zinnia
• Azalea and gardenia ( gt2.5ppm)

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Management of poor quality irrigation water is
necessary to produce high quality turfgrass