Biosolids are primarily organic, solid materials produced by wastewater treatment processes and
have value as nutrient sources or soil amendments. The material in this study was provided by the Metropolitan
Water Reclamation District of Greater Chicago.
Photos by Thomas Voigt
Thomas Voigt, Ph.D.; Guanglong Tian, Ph.D.; Albert Cox, Ph.D.; Pauline Lindo, Ph.D.; Kuldip Kumar, Ph.D.; and Thomas Granato, Ph.D.
Read this story in GCM's digital edition
Looking for an inexpensive way to fertilize and upgrade your roughs? A number of Chicagoland superintendents have found that using locally produced biosolids has improved turf at their course without impacting the budget's bottom line.
Biosolids are primarily organic, solid materials produced by wastewater treatment processes and have value as nutrient sources or soil amendments (1). The nitrogen in biosolids is mainly in organic form and has a slow rate of transformation to plant-available forms dependent on conditions that control the breakdown of organic matter by microbial activity. Biosolids also contain high amounts of phosphorus (1) and other plant nutrients including potassium, calcium, magnesium, sulfur and micronutrients.
Milorganite, a commercially available biosolids product available from the Milwaukee Metropolitan Sanitary District, has been used successfully in turfgrass management for many years. In this instance, the biosolids are digested aerobically, dried, screened and sterilized. Milorganite contains 6% nitrogen of which 92% is water insoluble.
In northeastern Illinois, the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) treats wastewater for an equivalent population of 10.35 million people in Cook County including the City of Chicago and 125 suburban communities. Founded in 1889 to protect Lake Michigan, the MWRDGC produces approximately 180,000 tons (dry weight) of biosolids annually.
Applying biosolids at the high rate (left) and the low rate (middle) produced turf that was rated as the same or darker
green than the check plot (right) at more than 80% of the evaluations.
These air-dried biosolids meet the United States Environmental Protection Agency's (USEPA) standards of exceptional quality (EQ biosolids), are made up of approximately 35% organic matter, and contain 1.5%-2.5% nitrogen, 2% phosphorus and 0.3%-0.5% potassium along with other essential plant nutrients such as iron, zinc, copper and sulfur. Presently, the concentration of heavy metal in MWRDGC biosolids is much lower than the USEPA's regulatory limits for EQ biosolids for land application, meaning that this product is safe for use in turf settings.
Biosolids research has shown its successful use as a topdressing fertilizer (3) and soil amendment for turf (4). In the Chicago area, golf courses have successfully used MWRDGC biosolids as a low-cost method for managing and improving turf performance (2,5). Based on the potential for greater biosolids demand and use by golf turf managers, we initiated this field research to answer the question, “Can locally produced biosolids be used as a low-cost fertilizer to manage and improve golf course rough performance?”
The field study
The field study began in September 2006 and continued through October 2008, with research plots being established in roughs at two Chicago-area golf courses, south-suburban Coyote Run Golf Course in Flossmoor, Ill., and 60 miles north at the Knollwood Golf Club in Lake Forest, Ill. A relatively new course, the 18-hole Coyote Run GC opened in 2005 following a total remodel of a previously existing 27-hole layout; our rough research was conducted on recently disturbed urban soils of mostly clay with little topsoil. Knollwood GC was founded in 1924, and the research-site soils were mature with a layer of topsoil present.
Kentucky bluegrass was the primary turf species on each research site, and the 5-foot × 10-foot (1.5-meter × 3-meter) plots were established in three replicates, not irrigated, maintained at 2-3 inches (5-7.6 centimeters), and grown in full or mostly full sun. The only chemical pest-control application was a postemergence broadleaf weed control herbicide application at Coyote Run in September of the first year, to control heavy weed populations.
There were eight treatments in the study (Table 1) consisting of two rates of MWRDGC biosolids; three commercial organic fertilizers (Nature Safe, Milorganite and Sustane); two commercial synthetic fertilizers (50% sulfur-coated urea and urea); and an untreated check. The two biosolids rates were selected to deliver 1 pound of total nitrogen/ 1,000 square feet (low biosolids rate) (4.88 grams/square meter) and 1 pound of plant-available nitrogen/1,000 square feet (high biosolids rate). At each application, all fertilizers except the high-biosolids-rate treatment were applied at 1 pound of actual nitrogen/1,000 square feet. Based on the assumption that approximately 20% of the total biosolids nitrogen becomes plant-available in the application season, the high-biosolids-rate treatment was applied at 5 pounds of product nitrogen/1,000 square feet (24.41 grams/ square meter) to provide 1 pound of available nitrogen during the season of application. The roughs were fertilized in May and September starting in September of the year before beginning the evaluations and continuing through September of the second study year. To ensure consistent biosolids nitrogen content throughout the study, biosolids from the same batch were stored for all applications.
The plots were evaluated monthly (April- October) for turf quality and color during both study years. Soil and turf tissue samples were collected for analysis at the study's start and at its conclusion in October of the second year. In the first year, no color evaluations were made in July, August or September and no quality evaluations in August or September at Coyote Run because of excessive broadleaf weed populations.
In our data analyses, the following contrast statements were developed to make statistical comparisons and determine statistical difference only between:
- the low biosolids rate and the commercial fertilizer treatments (Milorganite, Nature Safe, Sustane, 50% sulfur-coated urea and urea)
- the high biosolids rate and the commercial fertilizer treatments.
What did we learn?
Turf color was measured monthly (25 times) at Coyote Run and Knollwood over the two growing seasons. A Spectrum Technologies TCM 500 NDVI Turf Color Meter was used to record an average of six measurements per plot. This instrument measures reflected light from turf and provides a consistent measurement of turf color. Measurements were conducted on healthy turf only, and weedcovered portions or other aberrant areas of plots were avoided. In these ratings, both biosolids rates produced turf color that was the same as or darker green than the commercially available fertilizers at more than 80% of the evaluations and were also the same or darker green than the check plot at more than 80% of the evaluations (Table 2).
In the study, inconsistent particle size in the biosolids made application and coverage difficult, and the dust made application unpleasant. The air-dried biosolids can be
screened to a desirable particle size before use, and controlling the moisture levels in biosolids can significantly reduce the level of dust produced during application.
Turf quality, a combination of color, density, leaf width and uniformity, was evaluated 26 times over the two growing seasons and was rated subjectively using a scale of 1 through 9 (1 = dead turf, 9 = perfect turf, and 5 = minimally acceptable turf quality for the specific use) as used in National Turfgrass Evaluation Program evaluations. For the rough turf at Coyote Run and Knollwood, the low biosolids rate produced turf quality that was statistically the same as or higher than the commercially available fertilizers at 77% of the evaluations and at 69% of the evaluations for the high biosolids rate. Additionally, both of the biosolids rates produced turf that was the same or better quality than the check plot at 100% of the evaluations.
Monitoring warm-weather quality of coolseason Kentucky bluegrass can be useful. At cooler times of the year (an average of April, May, September and October evaluations), both biosolids rates produced turf quality that was comparable to or better than the commercially available fertilizers at 87% of the evaluations. During the warm months (June, July and August), the low biosolids rate produced turf quality that was comparable to or better than the commercially available fertilizers at 64% of the monthly evaluations, whereas the high biosolids rate was comparable or better at only 45% of the warm-season evaluations.
Turf tissue tests
Tissue testing can be used to identify mineral deficiencies in turf tissue. At monthly ratings, there were no obvious visual signs attributable to insufficient minerals in the turf fertilized with the high biosolids rate. This was confirmed by MWRDGC's laboratory testing conducted on shoot tissue samples collected from the research sites at the study's conclusion. Major mineral nutrients were present in sufficient quantities (Table 3) at all sites. While phosphorus levels in soils rose (Table 4), levels in turf tissues after two years of applications did not rise appreciably. In addition, sodium levels at Knollwood also rose and should be further evaluated in new studies to determine the long-term impact on turf.
There were no extreme changes in most soil chemical characteristics from the beginning of the study through its conclusion (Table 4). However, soil-extractable phosphorus levels increased over the two-year period. After the application of biosolids, soilextractable sodium increased at one site, but decreased at the other. A possible explanation for this increase was that the 2006 tests occurred on turf plots that had not been recently fertilized, whereas the 2008 soil samples were collected in October following a September fertilizer application and were only collected from the high-biosolids-rate plots, which received large amounts of biosolids to supply the 5 pounds of nitrogen. There was also a slight increase in the organic carbon content, which improves soil quality.
Evaluating biosolids characteristics when fertilizing turf
There are several characteristics to evaluate before applying biosolids to turf. First, as with other organic fertilizers in our study, the biosolids had a slight odor, which lasted for a few days after application. This slight odor immediately following application may be a concern to some turf managers or to golfers. Second, all of the commercial products were typically of uniform particle size, whereas the biosolids can be physically inconsistent if not screened before delivery and can contain dust-size particles when very dry. Inconsistent particle size in the batch of biosolids used in the study made application and coverage difficult, and the dust made application unpleasant. Particle size can be addressed by screening the air-dried biosolids to a desirable particle size before use. In addition, by controlling the moisture levels in biosolids, the production of dust during application is significantly reduced. Finally, following long-term biosolids applications, phosphorus can build up to levels that are more than the turf needs. However, phosphorus in biosolids is tied with iron oxides and has low water solubility. In addition, because turf is an effective interceptor and holder of applied materials, there should be little concern about phosphorus movement into surface water. Excessive levels of phosphorus from biosolids fertilizers, however, can create iron deficiencies resulting in reduced-quality turf, but is likely relieved by the iron in the biosolids (Tables 3, 4). For long-term sustainability, it is necessary to note that annually repeated high-rate application of biosolids at the same sites may not be recommended.
Overall, this research found that MWRDGC biosolids could be used to maintain rough turf at two Chicago-area golf courses. In fact, at more than 80% of the evaluations, the biosolids plots produced turf color that was equal to or better than several commonly used commercial organic and synthetic turf fertilizers and the check plots. Turf quality in the plots receiving the low biosolids rate (1 pound of nitrogen per application) performed similarly to or better than the commercial fertilizers and the check plots in most cases, even during summer evaluations. The high rate of biosolids (5 pounds of nitrogen per application), however, performed less well, especially in the summer months of the second growing season. Perhaps the combination of warm temperatures and the high application rate supplied excessive nitrogen, other minerals and/or salts as these materials built up over time. Additional studies evaluating rates between the low and high rates used in this study should be evaluated to fine-tune future applications.
A huge advantage of fertilizing with biosolids is cost. At the start of the study, there was no cost for the MWRDGC biosolids, while the golf course price per pound of actual nitrogen in the commercial products ranged from $0.53 per pound for urea to $4.83 per pound for Nature Safe (Table 1). If used to fertilize 30 acres of mowed rough turf with two pounds of nitrogen/1,000 square feet/year, the cost to apply urea would be $1,385.21 compared to $12,623.69 for Nature Safe; at the same time, there was no cost per pound of nitrogen in the MWRDGC biosolids because it was available at no cost.
Overall, it's little wonder that some Chicago-area superintendents are using MWRDGC biosolids in rough areas. Given both the turf management and financial value of this material, the wonder is why it's not more widely used.
Thanks to the Metropolitan Water Reclamation District of Greater Chicago for funding this research and to their Soil Science Section and Analytical Laboratory Divisions staff for providing lab analyses; superintendents Randy Wahler (Knollwood Golf Club) and Dave Ward (Coyote Run Golf Course) and their staffs for hosting this study and managing the research areas; and Kevin Armstrong, Shelby Henning, Rich Pyter and Emily Thomas of UIUC for data analyses and collection.
- Carrow, R.N, D.V. Waddington and P.E. Rieke. 2001. Turfgrass Soil Fertility and Chemical Problems: Assessment and Management. John Wiley & Sons, Hoboken, N.J.
- Dinelli, D. 2004. Compost scores high on golf course. BioCycle 45(7 ):52-54.
- Garling, D.C., and M.J. Boehm. 2001. Temporal effects of compost and fertilizer applications on nitrogen fertility of golf course turfgrass. Agronomy Journal 93(3):548-555.
- Linde, D.T., and L.D. Hepner. 2005. Turfgrass seed and sod establishment on soil amended with biosolids compost. HortTechnology 15(3):577-583.
- Tian, G., T.C. Granato, F.D. Dinelli and A.E. Cox. 2008. Effectiveness of biosolids in enhancing soil microbial populations and N mineralization in golf course putting greens. Applied Soil Ecology 40(2):381-386.
Thomas Voigt is an associate professor and Extension specialist in the department of crop sciences at the University of Illinois, Urbana, Ill. Guanglong Tian, Albert Cox, Pauline Lindo, Kuldip Kumar and Thomas Granato are all employees of the Metropolitan Water Reclamation District of Greater Chicago.