interpreting water quality reports
DESCRIPTION
Slides from a presentation February 17, 2011 at the Wyoming Groundskeepers and Growers Association annual conference.TRANSCRIPT
Interpreting WaterQuality Reports
Karen L. Panter, Ph.D., C.P.H.
Horticulture and Specialty Crops
Department of Plant Sciences
How do we measure water quality?
• Alkalinity• Salinity• pH• Sodium
Adsorption Ratio• Specific Ions• Suspended
Solids
Desirable Characteristics
• EC– <0.5 dS
• pH– 5.0 – 7.0
• Alkalinity– 40 – 100 ppm
• Nitrate– <5 ppm
• Magnesium– <24 ppm
• Ammonium– <5 ppm
• Phosphorus– <5 ppm
• Potassium– <10 ppm
• Calcium– <120 ppm
• Sulfates– < 240 ppm
Desirable Characteristics• Manganese
– <2 ppm• Iron
– <5 ppm • Boron
– <0.8 ppm • Copper
– <0.2 ppm • Zinc
– <5 ppm
• Molybdenum– <0.02 ppm
• Aluminum– <5 ppm
• Sodium– <50 ppm
• SAR– <4
• Chloride– <140 ppm
• Fluoride– <1 ppm
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Desirable Characteristics
pH• A pH reading is a
measurement of the hydrogen ion concentration of a solution– 0 most acid to 14
most basic– pH = 7 is neutral
• pH = 5.4 to 7.0 acceptable
[ ]pHH
= +
1
Salinity• Total dissolved
solids• Measured by
electrical conductivity– determined by
passing a current through the solution and determining its electrical conductance
– units are millimhos/cm, or
– decisiemens/meter (dS/m)
Salinity
• Restrictions to use:– < 0.25 dS/m None– 0.25-0.75 dS/m Moderate– 0.75-2.25 dS/m High– > 2.26 dS/m Severe
• Multiply by 700 to convert to ppm TDS– Total Dissolved Solids
Alkalinity
• The ability to neutralize acid (meq·L-1) or ppm (upper limits)– total carbonates (CO3 )– bicarbonates (HCO3 )– hardness (Ca + Mg)
• Restrictions to use (in meq·L-1):– < 2 None– 2-8.5 Slight to moderate– > 8.5 Severe
SAR - Sodium Adsorption Ratio
• Relates sodium to calcium and magnesium levels in water
• Must be done by water testing laboratory• Can lead to deficiencies in calcium and
magnesium
Sodium Adsorption Ratio• High sodium in relation
to calcium and magnesium can be detrimental to plant growth
• SAR should be < 10• Greenhouse < 4• Calcium may
precipitate
[ ][ ] [ ]
SARNa
Ca Mg=
+
+
+ +2 2
2
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Examples of Real Analyses
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And now….any questions?