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Field Science 38 SportsTurf | April 2015 www.sportsturfonline.com Field Science iRRiGATiOn & dRAinAGe and carbonate levels in irrigation water are less of a concern. However, high bicarbonate levels are associated with alkaline water, and have been implicated in the build-up of lime and calcium deficiencies in turf. Calcium deficiencies due to high bicarbonate levels in irrigation water are a source of debate in the turf industry, and there is very little research-based infor- mation on this topic in the Northeast. Thus, it's advisable to look at soil and plant tissue tests before assuming your turf is starving for calcium. Use of high bicarbonate-containing water (> 300 ppm) at the Penn State turf research facility over many years has resulted in water with a high pH (8.2 to 8.4), but we have not observed lime build up or calcium deficiencies in turfgrasses growing in sandy or silt loam soils. There may be several reasons for this, and one deals with how much calcium and magnesium is in the water. In many cases, there is more calcium and magnesium than bicarbonate on a charge basis in irrigation water, and in these situations calcium deficiencies are not likely to occur. Some water test labs, including Penn State's Agricultural Analytical Services Lab, perform a test called residual sodium carbonate or RSC, which tells you the amount of calcium and magnesium relative to bicarbonate and carbonate in irrigation water on a charge basis. If the RSC number is negative, you have more milliequivalents of calcium and magnesium than bicarbonate and carbonate in your irrigation water, and a low likelihood of calcium deficiency. An RSC value higher than 1.25 milliequivalents/L, indicates significant calcium may be tied up as lime. A survey of 100 turf irrigation water test reports in Pennsylvania revealed that 90% of the samples had negative RSC values. Of the 10 samples with positive numbers, none exceeded 1.25 meq/L. ElEctrical conductivity (Ec) and total solublE salts (tss) Electrical conductivity (EC) is a measure of the degree in which water conducts electricity, and provides an estimate of the amount of salts or ions in your water. It is determined by passing an electrical current through a water sample and recording the resistance in mmhos/cm or dS/m. The higher the EC, the higher the salt concentration of the water. EC is used to estimate total soluble salts (TSS) on your water test report through multiplying by a conversion factor (usually 640). TSS is sometimes reported as total dissolved salts (TDS), or as total dissolved solids (TDS); all three are calculated from EC using the same conversion factor. Acceptable TSS concentrations for turfgrass irrigation water range from 200 to 500 ppm (EC = 0.31 to 0.78 mmhos/ cm). TSS concentrations higher than 2,000 ppm (EC = 3.1 mmhos/cm) can severely damage or kill salt-sensitive turf- grasses. Although high salt-containing water is unusual in the northeastern US, increased use of recycled water or water con- taminated by seawater or runoff from heavily salted pavement in winter may be a concern in some areas. EC and TSS tell you the concentration of salts or ions in irrigation water, but they do not indicatewhich salts are pres- ent. Salt can refer to any ion, including calcium, magnesium, potassium, nitrate, bicarbonate, chloride, sulfate, sodium, and others. Some salts are more damaging to turfgrasses than oth- ers, so TSS alone does not provide all the information needed to assess the quality of your irrigation water. Some people mis- takenly assume that TSS refers to sodium, and apply gypsum or other calcium products to displace the sodium. Although sodium may contribute to high TSS, this ion should be con- sidered separately in your report. High EC or TSS-containing water should be mixed with cleaner water, or not used at all on turf. If you are forced to use irrigation water with a high TSS concentration, attention should focus on irrigation duration and frequency, improving drainage, and selecting turfgrass spe- cies with higher salt tolerance. Application of gypsum is not an effective remediation method for high TSS, unless sodium is the dominant ion. sodium absorption ratio (sar) The concentration of sodium relative to calcium and magne- sium is an important determinant of irrigation water quality. Calcium and magnesium play a major role in maintaining good structure of clay-containing soils, whereas high concentrations of sodium tend to destroy structure of clay in soils. If water Test your water, but look at your soil test reports, too Most water test laboratory reports list values or ranges of values that are considered outside the normal range of good quality irrigation water. These can be thought of as guideline values, and are warning signs of possible problems. However, just because a number on your test report exceeds guidelines for a particular factor does not necessarily mean you have poor water. Most of these values are generated from research done in irrigated crop- ping systems in arid regions of the southwestern US. In fact, very little research has been done to develop irriga- tion water guidelines for turf systems in other parts of the country. It's interesting to note that labs in the Northeast tend to use the same or similar guideline values as those in the southwestern US, where annual precipitation rates may be only 5-15 inches per year, and irrigation water is used in greater quantities than in the Northeast. Until more useful information is generated through research in turf and soils in cool, humid climates, we have to rely on informa- tion generated from arid regions. Given that we don't fully understand how some irrigation water quality factors will influence sports turf and soils in the northeastern region where irrigation is often used sparingly, it's a good idea to rely heavily on soil test reports for factors such pH, calcium, and salt concentrations in your soils.