Reference for Water Analysis 
 

 

Irrigation Water Guidelines

 

PARAMETER                      DEFINITION/RESULTS

pH                                           The degree of acidity (or alkalinity) of the sample. A pH of less than 7.0 is acidic, 7.0 is neutral and above 7.0 is alkaline. This needs to be adjusted (buffered) first, before tank mixing.

5.5 – 6.0 (ideal) provides the best conditions for irrigation & tank mixing.

                                    > 7.0 can cause tank mix problems.

Conductivity EC                   This test is used to determine the electrical conductivity (EC) of the water. The (electrical conductivity)         higher the salt content, the greater the flow of electrical current. The lower the 1 EC unit = 640 ppm                level, the more you can tank mix.

                                                < 1.5 desired range.

                                                > 1.5 potential problem.

                                                > 3.0 will burn under certain conditions.

 

Sodium Adsorption Ratio     The SAR measures the proportion of sodium to calcium and magnesium in

(SAR)                                     the water. It is also an index of the sodium hazard as water moves through the soil. A high sodium concentration disperses the soil clay and causes the soil to become hard and compact when dry and reduces the rate of water penetration when wet. High SAR on the infiltration of irrigation water depends on the electrical conductivity of the water. If the SAR is more than 10 times greater than the EC poor water infiltration will occur

                                                < 6.0 desired range (will add Ca to the soil).

                                                > 6.0 (will strip Ca from the soil); will burn under certain conditions; the                                                 lower the level, the more you can tank mix.

 

Calcium                                  Calcium cation is normally found in all natural water sources. When supplied                                                 with calcium, soil is friable and allows water to drain easily. Ca in the form                                                 of gypsum is applied to improve the physical properties of tight soils.                                                 Irrigation water that contains ample amounts of calcium is most desirable

                                                40 – 120 ppm desired range.

 

Magnesium                            Magnesium cation is normally found in all natural water. Magnesium can be                                                 used     to establish total salinity and estimate sodium hazard.

                                                6 – 24 ppm desired range.

 

Potassium                               Potassium cation behaves similarly to sodium in the soil and is commonly found                                                 in natural waters in only small amounts.

                                                5 – 10 ppm desired range.

 

Sodium                                   Sodium cation is often found in natural waters due to its high solubility. High                                                 concentrations of Na in soil can adversely affect turfgrasses causing poor physical                                   properties for plant growth in soil.

                                                0 – 50 ppm desired range.   

Iron                                         Iron cation can be a problem in irrigation waters. Excessive levels of iron cause                                                 staining of walkways and road surfaces and compete with other needed micro-                                                 nutrients.

                                                2 – 5 ppm desired range.

 

Total Alkalinity                     Water alkalinity measures the water's capability to neutralize added acids. Alkalinity establishes the buffering capacity of the water. Hi alkalinity can increase the pH of the soil 9reducing micro-nutrient availability), precipitation of nutrients in concentrated fertilizer solutions, and a reduced efficacy of pesticides and growth regulators.

                                                1 – 100 ppm desired range.

 

Carbonate                              Carbonates are salts of carbonic acid and are found in some waters. When                                     combined with calcium and/or magnesium an alkalizing effect occurs. This effect                           is stronger when coming in contact with sodium cation.

                                                < 50 ppm desired range.

 

Bicarbonate                           Bicarbonates are also salts of carbonic acid and are common in natural waters.                                     When moisture in soil reduces calcium and magnesium bicarbonates separate                                     from the clay colloid, leaving sodium to take its place. An increased SAR is the                                     result.

                                                < 120 ppm desired range.

 

Chloride                                 Chlorides contribute to the salinity content of soils and is found in irrigation                                                 water. High concentrations will inhibit plant growth and can be toxic to some                                                 plants, small concentrations is necessary for plant growth.

                                                < 140 ppm desired range.

 

Sulfate                                    Sulfate is common in water and has no major impact on the soil other than                                                 contributing to the total salt content.  Irrigation water high in sulfate ions reduces                                    phosphorus availability to plants.

                                                < 400 ppm desired range.

                                                > 400 ppm will acidify the soil.

 

Salt Concentration                The total dissolved solids (TDS) or total salt content is measured by determining                                                 the actual salt content in parts per million (ppm). A physiological drought                                                 condition can result from excess salts accumulating in the soil by increasing the                                                 osmotic pressure of the soil solution. Plants can wilt due to insufficient water                                                 absorption by the roots compared to the amount lost from transpiration, even                                                 though the soil may have plenty of moisture.

                                                (TDS = EC x 640)

                                                < 960 ppm desired range.

                                                > 1900 ppm or (3EC) = increased burn potential & poor tank mix options.

 

Boron                                     In small amounts boron is necessary for plant growth and is found in most waters.                                                 High concentrations of boron occur frequently therefore water must be tested to                                                 check for toxic amounts. Plant tolerance to boron may improve in soil high in                                                 lime, compare to non-calcareous soils.

                                                .2 – .8 ppm desired range.

 

Cation/Anion Ratio               Calcium and magnesium levels should always be higher than the sodium and                                                 chloride levels.

                                                1:1 ideal ratio.