Published online 27 April 2005
Published in Agron J 97:717-721 (2005)
DOI: 10.2134/agronj2004.0140
© 2005 American Society of Agronomy
677 S. Segoe Rd., Madison, WI 53711 USA
Soil and Water
Long-Term Effects of Recycled Wastewater Irrigation on Soil Chemical Properties on Golf Course Fairways
Y. L. Qiana,* and
B. Mechamb
a Dep. of Horticulture and Landscape Architecture, Colorado State Univ., Fort Collins, CO 80523-1173
b Northern Colorado Water Conservancy District, Berthoud, CO 80513
* Corresponding author (Yaling.Qian{at}colostate.edu)
Received for publication May 24, 2004.
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ABSTRACT
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The increasing water shortage in the arid and semiarid western USA requires use of recycled wastewater (RWW) when possible. Recycled wastewater has become a common water source for irrigating golf courses and urban landscapes, creating the need to study the effects of RWW irrigation on soil chemical properties. We compiled soil test data from fairways of 10 golf courses that were near metropolitan Denver and Fort Collins, CO. Among these courses, five had been irrigated exclusively with domestic RWW [electrical conductivity (EC) = 0.84 dS m–1] for 4, 13, 14, 19, and 33 yr, respectively. The other five with similar turf species, age ranges, and soil textures had used surface water (EC = 0.23 dS m–1) for irrigation. Our results indicated that soils (sampled to 11.4 cm) from fairways with RWW irrigation exhibited 0.3 units of higher pH and 200, 40, and 30% higher concentrations of extractable Na, B, and P, respectively. Compared with sites irrigated with surface water, sites irrigated with RWW exhibited 187% higher EC and 481% higher sodium adsorption ratio (SAR). Comparison of soil chemical properties before and 4 or 5 yr after RWW irrigation on two golf courses also revealed the following findings: (i) 89 to 95% increase in Na content; (ii) 28 to 50% increase in B content; and (iii) 89 to 117% increase in P content at the surface depth. Regular monitoring of site-specific water and soil and appropriate management are needed to mitigate the negative impacts of sodium and salts accumulations.
Abbreviations: CEC, cation exchange capacity • EC, electrical conductivity • ESP, exchangeable sodium percentage • RWW, recycled wastewater • SAR, sodium adsorption ratio • SOM, soil organic matter
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INTRODUCTION
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THE RAPID POPULATION growth in many municipalities in the arid and semiarid western USA continues to place increasing demands on limited fresh water supplies. Many cities and districts are struggling to balance water use among municipal, industrial, agricultural, and recreational users. The population increase has not only increased the fresh water demand but also increased the volume of wastewater generated. Treated or recycled wastewater appears to be the only water resource that is increasing as other sources are dwindling. Use of RWW for irrigating landscapes is often viewed as one of the approaches to maximize the existing water resources and stretch current urban water supplies (USEPA, 1992).
Often, recycled wastewater contains different levels of dissolved solids, nutrients (N and P), and other elements. Urban landscape plants, turfgrass in particular, need to be fertilized to maintain color, density, and vigor, although the amount of fertilizer applied annually depends on a number of factors (species, weather, soil, age, and clipping management). Nitrogen, P, and K are three important elements in maintaining a healthy turf stand with N producing the greatest growth response. Research done in the southwestern USA has indicated that dense, well-managed turfgrass areas are among the best bio-filtration systems available for removal of excess nutrients and further reclamation of recycled wastewater (Hayes et al., 1990; Pepper and Mancino, 1993).
Golf courses were the earliest and currently the leading urban landscape users of RWW in Colorado. Recently, this reuse practice has been extended to include some of the large parks, open spaces, and greenbelts (Qian, 2004). There is limited information available in Colorado concerning effects of irrigation with RWW on soil chemical characteristics. Most research addressing this issue has been conducted in the southern USA where the soil type and climate conditions are quite different from Colorado (Hayes et al., 1990; Mancino and Pepper, 1992). Research is needed to examine the impact of long-term RWW irrigation on soil chemical properties in cool arid and semiarid regions.
In this study, we (i) examine the soil chemical properties of five golf courses that have been irrigated with RWW for 4 to 33 yr, in comparison with five golf courses with similar age ranges, soil texture, landscape management regimes, and plant species, but use surface water for irrigation; and (ii) assess changes in soil chemical properties after 4 to 5 yr of RWW irrigation on two selected golf courses.
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MATERIALS AND METHODS
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Study Sites
Ten golf courses in the Denver and Fort Collins, CO, area were selected for the study. Colorado has a semiarid climate. The average annual precipitation is 36 and 40 cm in Fort Collins and Denver, respectively. The main soil series and surface texture for the 10 sites were obtained with the assistance of the Natural Resources Conservation Service (NRCS) of the USDA (Table 1). All of the golf courses were in a mesic soil temperature regime.
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Table 1. Age, years of recycled wastewater irrigation (RWI), principle soil series, and surface texture of principle soil series of golf courses selected for the project to evaluate long-term recycled wastewater (RWW) irrigation on soil properties and landscape plant health.
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Among these courses, five had been irrigated with RWW for 4, 13, 14, 19, and 33 yr, respectively, in 2003 (Table 1). On all recycled wastewater irrigation sites, RWW from wastewater treatment plants are stored in irrigation ponds and used exclusively as the irrigation source. Turfgrass grown on fairways were perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), or a mixture of both. Fairways received approximately 65 cm of RWW and were fertilized at 75 kg ha–1 N annually. Gypsum was applied at 0.5 to 2.7 Mg ha–1 on fairways annually. At Golf Course II an acid injection unit was used, and at Golf Course I and III sulfur burner units were installed in the irrigation systems. The acid injection unit injects sulfuric acid into irrigation water as irrigation water enters the pump systems. Sulfur burner units heat elemental sulfur to create sulfurous acid that is injected into irrigation water. Both acid injection and sulfur burner units were installed to reduce the bicarbonate content and pH of irrigation water.
Five golf courses with similar ranges in age, soil texture, landscape management regimes, and plant species, but irrigated with surface water were selected as controls (Table 1). Most of the surface water comes from melting snow of the Rocky Mountains and exhibits good quality (Table 2). Control courses were fertilized with about 150 kg ha–1 N annually. Turfgrass received approximately 55 cm of irrigation water annually. Gypsum was not applied. The average water quality values of surface water and recycled wastewater (RWW) used in the 10 selected golf courses are presented in Table 2.
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Table 2. Average water quality values of ditch water and recycled wastewater (RWW) from advanced wastewater treatment plants in Colorado.
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Soil Sampling from Recycled Wastewater–Irrigated vs. Surface Water-Irrigated Sites
A total of 105 soil samples (54 samples were from golf courses with RWW irrigation and 49 were from golf courses with surface water irrigation) were collected to a depth of 11.4 cm from fairways of these golf courses in 2002–2003 to test soil chemical properties. This sampling depth is very common in golf courses where turf is mowed to less than 2.5 cm height and majority of turfgrass roots are concentrated in the surface 10 cm. Soil samples were tested by Brookside Laboratories, New Knoxville, OH. Parameters of each soil sample tested included pH; extractable salt content (Ca, Mg, K, Na, Fe, Mn, Cu, Zn, P, and B); base saturation percent of Ca, Mg, K, and Na; soil organic matter (SOM) content; and cation exchange capacity (CEC).
Brookside soil-testing lab provided information on analytical methods. Soil pH was analyzed using a saturated paste extract. Sieved soil samples were extracted using the Mehlich III extractant (0.015 M NH4F + 0.20 M CH3COOH + 0.25 M NH4NO3 + 0.013 M HNO3 + 0.0005 M EDTA chelating agent) to determine Ca, Mg, K, Na, Fe, Mn, Cu, Zn, B, and P by inductively coupled plasma–emission spectrophotometry instrumentation. Mehlich III extracted Ca, Mg, K, and Na plus soil buffer pH data are used to calculate CEC. Base saturation percent of Ca, Mg, K, and Na was calculated by dividing the extracted Ca, Mg, K, and Na by the calculated CEC, respectively. Base saturation percent of Na is considered the exchangeable sodium percentage (ESP). Soil organic matter was determined by reaction with Cr2O72– and sulfuric acid. The remaining unreacted Cr2O72– is titrated with FeSO4 using ortho-phenanthroline as an indicator, and oxidizable organic matter was calculated by the difference in Cr2O72– before and after reaction (Nelson and Sommers, 1982).
In 2004, three additional soil samples from each site were collected to measure soil EC and SAR of saturation paste in the Soil, Plant, and Water Analytical Lab at Colorado State University. Electrical conductivity of soil saturation paste extract was determined with a conductivity meter. Cation (Ca, Mg, and Na) concentrations of saturation paste extracts were analyzed by inductively coupled plasma–emission spectrophotometry instrumentation and SAR was calculated.
Soil Tests Before and 4 or 5 Years after Recycled Wastewater Irrigation
At Golf Course I and Golf Course II, soil samples were collected before (1999 and 1986, respectively) and 4 or 5 yr after the commencement of recycled wastewater for irrigation (2003 and 1991, respectively). Soil sampling depth and soil analysis protocols were the same as previously described. The before and after comparisons provide indications about the impacts of RWW irrigation on soil chemical properties. However, one of the disadvantages of the before and after comparison of soil chemical properties is the inability to separate the effects of RWW constituents and the effects of irrigation water itself.
Data Analysis
Data were subjected to analysis of variance (SAS Institute, 1991) to test the effect of irrigation water source on individual soil chemical characteristics. Significant differences in soil chemical properties before and 4 or 5 yr after RWW irrigation were also determined using an analysis of variance (P < 0.05).
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RESULTS AND DISCUSSION
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Comparison of Reuse Sites vs. Surface Water Irrigated Sites
Sites irrigated with RWW exhibited an average soil salinity 4.3 dS m–1 that was 187% higher than site irrigated with surface water (EC = 1.5 dS m–1) (Table 3). Variations in increase in EC under RWW irrigation appeared to relate to soil texture and drainage effectiveness (data not shown). Previously, Qian et al. (2001) reported that the salinity levels that caused 25% shoot growth reduction were 3.2 dS m–1 for a salt-sensitive Kentucky bluegrass cultivar and 4.7 dS m–1 for a salt-tolerant Kentucky bluegrass cultivar. It is apparent that the salinity build-up in sites irrigated with RWW would result in growth reduction of salt sensitive Kentucky bluegrass cultivars that may slow the recovery of turf from traffic injury and/or other biotic and abiotic stresses. We have observed salinity stress for sites with long-term RWW irrigation, especially for sites with fine soil texture and poor drainage. Several fairway sites on Golf Course IV, which had been irrigated with RWW for 33 yr, were replaced by more salt-tolerant grass, such as alkaligrass [Puccinellia distans (L.) Parl].
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Table 3. Mean soil chemical properties from golf courses with long-term recycled wastewater irrigation vs. surface water irrigation.
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Soils from sites with RWW for irrigation exhibited 200% (278 mg kg–1) higher concentration of extractable Na and 24% higher concentration of extractable Ca than sites irrigated with surface water (Table 3). The high Na content reflected the greater than sixfold increase in Na via RWW. The average Na concentration of over 30 RWW samples collected was 99 mg L–1, ranging from 30 to 170 mg L–1 (Table 2). The higher Ca in RWW-irrigated sites than the control sites likely resulted from the combination of a 3.8-fold higher concentration of Ca in RWW and the regular application of gypsum. Higher Ca and Mg in the RWW combined with gypsum application helped prevent a greater degree of Na built up in the soil.
Extractable P at the surface 11.5 cm depth was 30% higher from sites with RWW irrigation than sites with surface water irrigation (Table 3). Runoff of P was likely to be minimal from turf sites due to the dense vegetation cover that could effectively prevent P runoff.
Soil pH was higher (approximately 0.3 units) in RWW-irrigated sites than in the control sites. Increases in soil pH under land application of wastewater have been previously reported (Schipper et al., 1996; Mancino and Pepper, 1992). In New Zealand, Schipper et al. (1996) found an increase in soil pH by 0.8 units after applying tertiary-treated domestic wastewater to a forest site for 3 yr at 4.9 cm wk–1. The author suggested that the rise in soil pH was likely related to a high rate of denitrification that produced hydroxyl ions. Mancino and Pepper (1992) found that effluent water irrigation increased soil pH by 0.1 to 0.2 units when compared with potable water irrigation. The soil pH increase in our study likely resulted from the 0.2 unit higher pH and higher bicarbonate concentration in RWW than surface water. The average bicarbonate concentration in the RWW was 112 mg L–1. The small magnitude of increase in soil pH in this study suggests the effectiveness of management (such as using acid injection and utilization of a sulfur burner) in controlling soil pH. Golf Courses IV and V that did not receive acidification treatments exhibited 0.3 to 0.4 units higher soil pH than other RWW-irrigated sites (data not shown).
Soil B content was about 40% higher in the RWW-irrigated sites than in surface water–irrigated sites. Although the average B concentration in the RWW was only 0.23 mg L–1, lower than the permissible limits for the allowable concentration of B in irrigation water presented by Van der Leeden et al. (1990), we consistently observed an increase in B content in the soil. Likely the accumulation of B was associated with the borate adsorption by soil. With increasing soil pH, B adsorption by soil would increase, reaching the maximum B adsorption by soil at a pH of 9 (Ayers and Westcot, 1985).
Despite the fact that Mg content was twofold higher in RWW than surface water (Table 2), soil Mg content was 15% lower in RWW-irrigated sites than the control sites (Table 3). The cation exchange site occupied by Mg was reduced, reflecting the replacement of this element with Na. In addition, application of gypsum might also reduce soil exchangeable Mg2+ since Ca2+ has much higher adsorption affinity than Mg2+.
The ESP and SAR for RWW irrigated sites was 230 and 481% higher than the surface water–irrigated soil, respectively (Table 3). Soil ESP and SAR would have continued to increase without the regular amendment of Ca products. In soil collected from the rough at Golf Course II that was not amended with Ca products, the ESP rose to as high as 15.0. Although the ESP and SAR values on fairways are not high enough to be classified as a sodic soil, Halliwell et al. (2001) stated that the dispersion and deflocculation effects of sodicity might be evident in soils that are well below reported threshold values. Long-term uses of RWW with marginal high SARadj may result in reductions of soil infiltration and permeability in clayey soils and for sites with high traffic and compaction pressure. Further research is needed to monitor soil hydraulic properties for sites irrigated with RWW.
Our results indicated predominant differences in soil SAR; EC; ESP; extractable soil Na, Ca, P, B, and Mg concentration; and soil pH between RWW-irrigated and surface water–irrigated sites (P < 0.05). Differences in CEC, SOM, and K content between the two types of irrigation sites were not significant.
Soil Analysis at Two Golf Courses before and 4 to 5 Years after Recycled Wastewater Irrigation
At Golf Course I, we observed an increase of Na by 247 mg kg–1 (95%) after 4 yr of irrigation with RWW (Table 4). This is higher than the Na increase observed in a sandy loam soil at Golf Course II. Mancino and Pepper (1992) reported an increase of water-extractable Na content by 155 mg kg–1 after 3.2 yr of using RWW in a bermudagrass [Cynodon dactylon (L.) Pers.] fairway in Arizona. The increase in soil Zn (by 109%), B (by 50%), and P (by 90%) content after 4 yr of RWW irrigation were also significant (Table 4). The increased Na, Zn, B, and P in the soil solution reflected the characteristics of RWW. We did not observe significant differences in soil pH or K content. The addition of a S burner in the irrigation system appeared to effectively prevent the increase of soil pH by RWW for irrigation.
At Golf Course II, soil Na, Mg, Mn, P, B, and K content were increased by 181, 148, 14, 32.2, 0.26, and 255 mg kg–1, respectively, after 4 yr irrigation with RWW (Table 5). These corresponded to 90, 44, 23, 88, 28, and 35% increase. We also observed an increased SOM after 5 yr of RWW irrigation, which likely resulted from input of organic C from turfgrass roots and thatch (Qian and Follett, 2002).
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SUMMARY
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Both opportunities and problems exist in using RWW for landscape irrigation. Recycled wastewater irrigation in urban landscapes is a powerful means of water conservation and nutrient recycling, thereby reducing the demands of freshwater and mitigating pollution of surface and ground water. However, potential problems associated with recycled wastewater irrigation do exist. These problems include salinity build up and relatively high Na and B accumulation in the soil. Especially, the significantly higher soil SAR in RWW-irrigated sites compared with surface water irrigated sites provided reason for concern about possible long-term reductions in soil hydraulic conductivity and infiltration rate in soil with high clay content, although these levels were not high enough to result in short-term soil deterioration. Salt leaching would become less effective when soil hydraulic conductivity and infiltration rate were reduced. These chemical changes may in part contribute to the stress symptoms and die off observed in some ornamental trees and, to a lesser degree, in Kentucky bluegrass–perennial ryegrass turf on all the five study sites that have been subjected to long-term RWW irrigation.
As more landscape facilities and development areas plan to switch to recycled wastewater for irrigation, landscape managers must be prepared to face new challenges associated with the use of recycled wastewater. Persistent management practices, such as applications of soil amendments that provide Ca to replace Na; periodic leaching to reduce salt accumulation; frequent aerifications to maintain infiltration, percolation, and drainage; regular soil and plant monitoring, and selection and use salt-tolerant turfgrass and landscape plants will be helpful in mitigating the negative impact and ensuring continued success in using RWW for landscape irrigation.
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NOTES
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This report was financed in part by the U.S. Department of the Interior, Geological Survey, through the Colorado Water Resources Research Institute and Grant no. 01HQGR0077. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. government.
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REFERENCES
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- Ayers, R.S., and D.W. Westcot. 1985. Water quality for agriculture. FAO irrigation and drainage paper No. 29. Food and Agriculture Organization of the United Nation, Rome.
- Halliwell, D.J., K.M. Barlow, and D.M. Nash. 2001. A review of the effects of wastewater sodium on soil physical properties and their implications for irrigation systems. Aust. J. Soil Res. 39:1259–1267.[CrossRef]
- Hayes, A.R., C.F. Mancino, and I.L. Pepper. 1990. Irrigation of turfgrass with secondary sewage effluents: I. Soil and leachate water quality. Agron. J. 82:939–943.[Abstract/Free Full Text]
- Mancino, C.F., and I.L. Pepper. 1992. Irrigation of turfgrass with secondary sewage effluent: Soil quality. Agron. J. 84:650–654.[Abstract/Free Full Text]
- Nelson, D.W., and L.E. Sommers. 1982. Total carbon, organic carbon, and organic matter. In A.L. Page et al. (ed.) Methods of soil analysis. Part 2. Agron. Monogr. 9. ASA, Madison, WI.
- Pepper, I.L., and C.F. Mancino. 1993. Irrigation of turf with effluent water. p. 623–641. In M. Pessarakli (ed.) Handbook of plant and crop stress. Marcel Dekker, New York.
- Qian, Y.L. 2004. Urban landscape irrigation with recycled wastewater: Preliminary findings. Colorado Water 21(1):7–11.
- Qian, Y.L., and R.F. Follett. 2002. Assessing soil carbon sequestration in turfgrass systems using long-term soil testing data. Agron. J. 94:930–935.[Abstract/Free Full Text]
- Qian, Y.L., S.J. Wilhelm, and K.B. Marcum. 2001. Comparative responses of two Kentucky bluegrass cultivars to salinity stress. Crop Sci. 41:1895–1900.[Abstract/Free Full Text]
- SAS Institute. 1991. SAS/STAT user's guide. SAS Inst., Cary, NC.
- Schipper, L.A., J.C. Williamson, H.A. Kettles, and T.W. Speir. 1996. Impact of land-applied tertiary-treated effluent on soil biochemical properties. J. Environ. Qual. 25:1073–1077.[Abstract/Free Full Text]
- USEPA. 1992. Manual: Guidelines for water reuse. USEPA Rep. 625/R-92/004. USEPA, Washington, DC.
- Van der Leeden, F., F.L. Troise, and D.K. Todd. 1990. The water encyclopedia. 2nd ed. Lewis Publ., Boca Raton, FL.
- Westcot, D.W., and R.S. Ayers. 1985. Irrigation water quality criteria. p. 3:1–36. In G.S. Pettygrove and T. Asano (ed.) Irrigation with reclaimed municipal wastewater: A guidance manual. Lewis Publ., Chelsea, MI.
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ABSTRACT
INTRODUCTION
