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pH of Water Sample
5.5 - 6
Sodium Absorbtion Ratio (SAR)
< 6 ppm
1 - 100
1 - 50
0 - 120
0 - 140
0 - 400
40 - 120
6 - 24
5 - 10
0 - 50
.2 - .8
2 - 5
.5 - 2
0 - .2
1 - 5
Irrigation Water Guidelines
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.
> 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
Magnesium Magnesium cation is normally found in all natural water. Magnesium can be used to establish total salinity and estimate sodium hazard.
Potassium Potassium cation behaves similarly to sodium in the soil and is commonly found in natural waters in only small amounts.
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.
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.
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.
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.
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 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)
> 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.
Cation/Anion Ratio Calcium and magnesium levels should always be higher than the sodium and chloride levels.