Cover Story

Survey of Turfgrass Irrigation Water Quality in Pennsylvania

By Peter Landschoot, John Spargo, and Benjamin McGraw

This article is a condensed summary of results from a survey of turfgrass irrigation water in Pennsylvania. The complete survey is published in Crops, Forages, and Turfgrass Management and can be accessed at:

https://acsess.onlinelibrary.wiley.com/doi/full/10.1002/cft2.20157?af=R

Irrigation is a vital management practice for golf courses, sports turf facilities, and lawns throughout the United States. A survey conducted in 2013 by the Golf Course Superintendents Association of America revealed that golf courses in the northeast United States, including Pennsylvania, used approximately 30.7 billion gallons of water (4). Although water use by golf courses in the northeast is generally much less than in the southern United States, population growth and competition for water from businesses and industry has resulted in increased costs and scrutiny of turfgrass irrigation practices by regulatory agencies. In the future, turfgrass managers in Pennsylvania may be forced to use more recycled or marginal quality water, which will likely involve frequent testing of irrigation water and reliance on advice from private consultants, university specialists, and test laboratory personnel.

In 2007, Penn State’s Agricultural Analytical Services Laboratory (PSAASL) began a testing program for drinking and irrigation water as a service to individuals in Pennsylvania and the nearby states. Although studies of drinking water quality in Pennsylvania have been published (7,8), data summaries of turfgrass irrigation water quality are generally not available to the public.

The main objective of this survey was to create a baseline profile of turfgrass irrigation water quality in Pennsylvania that can be used for comparison with data from other regions or future water quality surveys within Pennsylvania. A secondary objective was to establish “normal range” guidelines for test reports corresponding to values falling within 90th and 10th percentiles for 24 irrigation water quality parameters. Normal ranges can serve as references for practitioners and consultants when comparing irrigation water quality used at one facility with the range of values generated from water samples collected throughout Pennsylvania.

Collection and Analysis of Irrigation Water Samples

Volunteers, including research technicians, extension educators, turf product distributors, and irrigation specialists collected water samples from turfgrass irrigation water sources in Pennsylvania. Samples were taken directly from irrigation system valves (“quick couplers”) after 30 to 60 seconds of flushing, or from ponds, rivers, and streams as close to intake ports as possible. Sources composed of effluent or recycled wastewater, or water amended with acid, fertilizer, or any other substance were excluded from this survey.

Samples were collected from golf courses (174), sports turf facilities (12), sod farms (2), a turfgrass research facility (1), and a large display garden (1) from 2007 to 2019. Only one sample was collected from each facility unless multiple irrigation water sources were used, in which case one sample was collected from each source. Samples were collected from 50 of the 67 counties in Pennsylvania, with most taken from counties with numerous golf courses. All 190 samples collected for this survey were analyzed for pH, alkalinity, hardness, electrical conductivity (EC), total dissolved solids (TDS), sodium, sodium adsorption ratio (SAR), bicarbonate, carbonate, calcium, magnesium, residual sodium carbonate (RSC), chloride, and boron. Of the 190 samples, 180 were also analyzed for nitrate-N, ammonium-N, phosphorus, potassium, sulfur, iron, manganese, copper, molybdenum, and zinc.

Water quality parameter median values were used as the descriptive measure of central tendency and data were further segmented into quartiles, as well as the 95th, 90th, and 10th percentiles (Table 1). Irrigation water quality data collected in this survey are intended to provide a broad profile of water quality over a range of sources, in different years and months of the growing season, and across regions with varying geology and topography.

Summary of Irrigation Water Survey Results

pH and alkalinity

Irrigation water can be classified as acid, neutral, or alkaline. Any pH value below 7.0 is considered acid, a value of 7.0 is neutral, and a pH above 7 is alkaline. Survey results show that irrigation water pH ranged from 6.4 to 10.3, with a median of 7.7 (Table 1). 90% of the samples were equal to or below 8.3, and only 10% were equal to or below 7.1.

Alkalinity represents the neutralizing capacity of water and if present in adequate amounts, buffers freshwater in the approximate pH range of 6.0 to 8.5 (5,9,11). When alkalinity falls below 20 mg/L of CaCO 3, water can undergo wide daily and seasonal pH fluctuations, causing stress, poor development, and sometimes the death of aquatic animals (9,11).

Irrigation water survey data show an alkalinity range from 4 to 340 mg/L of CaCO 3 with a median value of 77 mg/L (Table 1). Results indicate 90% of the samples were equal to or below 167 mg/L CaCO 3 and 10% were equal to or below 29 mg/L. Only two irrigation water samples in this survey had total alkalinity values below 20 mg/L CaCO 3, and both samples were from ponds on golf courses. This survey-based normal range falls within the published normal range of 20 to 300 mg/L of CaCO 3 for turfgrass irrigation water given by Carrow and Duncan (2).

Electrical conductivity (EC) and total dissolved solids (TDS)

Two water quality indicators used to express soluble salts in turfgrass irrigation test reports are EC and TDS. EC is a measure of the degree in which water conducts electricity. It is determined by passing an electrical current through a water sample and recording the resistance in mmhos/cm or dS/m. EC is used to estimate TDS in ppm or mg/L in water using the equation: TDS (mg/L) = EC (dS/m) x 640. EC and TDS provide an indication of dissolved salts but do not indicate which salts are present in the water. Acceptable TDS values for turfgrass irrigation water range from 200 to 500 mg/L (EC ~ 0.31 to 0.78 dS/m) (2). TDS values higher than 2,000 mg/L (EC ~ 3.1 dS/m) can damage turfgrasses (2). If using irrigation water with a TDS concentration higher than 500 mg/L, attention should focus on irrigation duration and frequency, drainage, and turfgrass species selection.

TDS values in this survey ranged from 31 to 883 mg/L, with a median value of 218 mg/L (Table 1). Only 10% of the samples had a TDS value at or below 70 mg/L, whereas 90% of the samples had a TDS at or below 480 mg/L. Seventeen of the 190 samples analyzed in this survey exceeded 500 mg TDS/L, which is sometimes considered a threshold for stress in salt-sensitive plants such as annual bluegrass and Kentucky bluegrass in arid climates. Whereas the 500 mg TDS/L threshold for salt-sensitive turfgrasses may be a concern in arid regions where irrigation amounts are high, it may be less of a concern in Pennsylvania, where natural precipitation is close to 40 inches per year and irrigation amounts tend to be lower.

Sodium and sodium adsorption ratio (SAR)

Sodium concentrations in irrigation water survey samples ranged from 0.5 to 97 mg/L with a median of 15 mg/L (Table 1). Of the 190 samples included in this survey, 95% had sodium concentrations at or below 70 mg/L, the upper limit listed in PSAASL water analysis reports. The survey results showed that 90% of the samples had sodium concentrations equal to or below 47 mg/L and 10% were equal to or below 3 mg/L.

SAR provides a useful indicator of the potential damaging effects of sodium on soil structure and permeability. SAR is calculated using a formula that accounts for the chemical weight and charge of sodium, calcium, and magnesium. SAR values below 3 are generally considered acceptable for turfgrass sites (5). Survey results show that SAR values ranged from 0.04 to 2.76, with a median of 0.61 (Table 1). The survey indicates that 90% of the samples had SAR values equal to or below 1.7 and 10% were equal to or below 0.12. All water samples in this survey had SAR values below 3.0.

Bicarbonate, carbonate, and residual sodium carbonate (RSC)

Bicarbonate and carbonate concentrations are typically reported in irrigation water test reports for determining the potential for enhanced sodium-related soil permeability problems when SAR values are high, or when the formation of calcite in the soil or on the surface of putting greens, increasing soil pH, and iron chlorosis are of concern (3).

Bicarbonate concentrations in this survey ranged from 0 to 414 mg/L, with a median value of 87 mg/L (Table 1). Results show that 90% of the samples had less than or equal to 202 mg bicarbonate/L and 10% had less than or equal to 29 mg bicarbonate/L. Carbonate was detected in only 8 of 190 samples and ranged from 0 to 39 mg/L. Carrow and Duncan (2) stated that bicarbonate and carbonate concentrations in irrigation water are highly variable and suggested that bicarbonate may be a concern at levels above 120 mg/L, especially when sodium concentrations are high. However, when sodium concentrations are not high, bicarbonate values higher than 120 mg/L do not necessarily indicate that the water is of poor quality for irrigation. Approximately 40% of survey samples had bicarbonate values greater than 120 mg/L.

RSC values are generated by subtracting the sum of calcium and magnesium expressed in meq/L from the sum of bicarbonate and carbonate in meq/L. A negative RSC value indicates that on an equivalent weight basis, there is more calcium and magnesium in the irrigation water than bicarbonate and carbonate, whereas a positive value indicates that bicarbonate and carbonate in irrigation water have precipitated all or most of the calcium and magnesium ions (3). Positive values exceeding 2.50 meq/L suggest that the irrigation water is not suitable for use if the sodium and SAR are at levels that can cause soil permeability problems (3,5). The range of RSC values in this survey was −10.6 to 0.9 meq/L and the median value was −0.8 meq/L (Table 1). Based on the 90th and 10th percentile values found in this survey, the proposed normal RSC range for irrigation water in Pennsylvania is −0.1 to −2.4 meq/L. Only 12 of the 190 samples analyzed in this survey had positive RSC values and none exceeded 0.9 meq/L.

A secondary concern expressed by some turfgrass practitioners is that the bicarbonate and carbonate in irrigation water will bind to calcium and magnesium, thus reducing calcium’s availability to turf and forming surface calcite or carbonate-cemented layers that reduce permeability in golf course putting greens. Although carbonate-cemented layering in soils may be problematic in arid regions, research-based information to substantiate these concerns in turfgrass systems in cool, humid regions of the United States is limited (6,10). Research conducted at the University of Wisconsin involving 28 sand-based putting greens with differing geographical features found no evidence that bicarbonate from irrigation water formed carbonate-cemented layers or zones of accumulation (6). Given that none of the RSC values in survey samples exceeded 0.9 meq/L, and the limited research-based information concerning bicarbonate-induced calcium deficiencies and soil sealing problems in cool, humid regions such as Pennsylvania and the surrounding states, the 120 mg/L upper limit for bicarbonate listed on many irrigation water test reports may be unnecessarily conservative.

Chloride

Survey results showed that chloride ranged from less than 1 to 221 mg/L, with a median of 26 mg/L (Table 1). 90% of the samples had chloride concentrations at or below 97 mg/L, and 10% were at or below 4 mg/L. The 4 to 97 mg chloride/L normal range is very close to the 0 to 100 mg/L desired range listed by Duncan et al. (3).

Conclusions

This survey aimed to establish a baseline profile of turfgrass irrigation water quality from nonamended and noneffluent sources in Pennsylvania that can be compared with water quality data from other geographic regions and future surveys in the Commonwealth, and to improve test report guidelines for samples submitted to water testing laboratories. Results show acceptable irrigation water quality according to published guidelines with some exceptions, including high values for sodium, TDS, and chloride, but these were less than or equal to 10% of the samples. Data from this survey were used to establish normal ranges for the 24 water quality parameters examined. Normal ranges for the quality parameters of turfgrass irrigation water in Pennsylvania are likely to differ from those in other areas of the United States. In the case of pH, alkalinity, and bicarbonate, normal ranges should be expanded to account for the numerous water samples (> 45%) that exceeded the ranges listed in some water test reports. Normal ranges can serve as references for practitioners and consultants when comparing the irrigation water quality used at one facility with the range of values generated from water samples collected throughout Pennsylvania.

Acknowledgements

The authors thank the following individuals for collecting the water samples for this survey: George Skawski, Eric Kline, Danny Kline, Jeff Gregos, Don Lipandro, Robert Capranica, Tanner Delvalle, Thomas Bettle, and Christopher Marra. Financial support for this research was provided by the Stanley J. Zontek Endowment and the Pennsylvania Turfgrass Council.

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