Turfgrass management of public lands is a complex endeavor that involves balancing functional and aesthetic goals of the turf with community expectations, economics, environmental impact, and human health risk. Individuals and stakeholders often disagree on the functional and aesthetic goals and degree of acceptable impacts and risks. In addition, budgets often constrain the range of management options available to meet goals.
Recently, we had a unique opportunity to demonstrate some different options for turfgrass management in Stoughton, WI where a local sustainability group had been challenging the city to reduce pesticide use in parks. Interestingly, representatives of both the sustainability group and the City of Stoughton Parks Department reached out to Extension Specialists at the University of Wisconsin-Madison asking for information and help with the conflict. We felt that a multi-year demonstration of some different approaches to turfgrass management on one of the City’s sports complexes might be a good way to facilitate some communication between the Parks Department and the sustainability group and hopefully identify some common ground.
It is important to understand this project was a demonstration, not a scientific study. A study would require replications and uniform field conditions including an even distribution of traffic, both of which were lacking in this demonstration. For example, Field 4 had only 8% weed cover immediately before study initiation, while Fields 2 and 3 were around 65% weeds. In addition, Fields 1 and 2 were the only with lights, so they received more traffic than the other two. Because of the excellent condition and low traffic level of Field 4, we selected this as the control treatment where no fertilizers or pesticides would be used during the trial. We felt it would be important to demonstrate the impact of neglect, and starting with the best field seemed like a good way to make that point.
Fortunately, the fields had uniformly good soil conditions with pH in the ideal range (6.0 – 7.0), and within or just outside of optimal levels of plant available phosphorus (38-50 ppm) and potassium (121-160 ppm). The organic matter content averaged 4.4%, which is considered excellent.
Four application strategies
The four application strategies were randomly assigned to the four fields characterized above. Field 1 became the Organic Program, Field 2 became the City of Stoughton Program, Field 3 became the UW Integrated Turfgrass Management Program, and Field 4 became the Mowing Only Program. Applications were scheduled to be consistent with the capabilities and budget of the City of Stoughton’s budget for parks. On June 4, 2015, fertilizers and herbicides were applied to Fields 1 and 2. University of Wisconsin staff made the applications to the Organic Program (Field 1), and WeedMan Lawn Care made the applications to Field 2. The City of Stoughton program was applied on June 29, 2015, by TruGreen. Unfortunately, a miscommunication resulted in TruGreen also applying herbicide and fertilizer to the Organic Program field on June 29. No applications to any fields were made in 2016. Applications to Fields 1 and 2 were made on May 16, 2017. The City of Stoughton program was applied on May 15 and October 9, 2017, by Insight FS.
We conducted visual ratings of turfgrass quality and made weed assessments in spring, summer, and fall each season. Visual quality was recorded for each field where 1 represents completely dead or brown turf, 9 represents the highest possible turfgrass quality, and 6 represents minimally acceptable turfgrass quality. Weeds were evaluated at six randomly selected locations in each field and then averaged.
In general, the three fertilized treatments have maintained turfgrass quality around the minimally acceptable level, sometimes rising above, other times dipping just below. However, the field that has been neglected (mowed only) slowly declined from a visual quality of 5 to 4 over the past three seasons. These results suggest that the three fertilization strategies are capable of producing approximately equal and acceptable turfgrass quality. The mowing only treatment has demonstrated that fertilization is a necessary step for maintaining acceptable quality.
Weed percentages were relatively low at all fields near the beginning of the study. A decline in weed population was observed in 2015 for all but the neglected field (a conventional herbicide was accidentally applied to the organic field in 2015). Weed populations rose in 2016, a season that saw no fertilizer or herbicide applications on any of the fields. In 2017, weed populations declined in the standard and UW Integrated fields, while rising sharply in the organic field. In July 2017, weed populations were <10% in the herbicide treated fields and 40-55% in the Organic and Mowing Only Programs.
In conclusion, we found that all three fields treated with fertilizer produced acceptable turfgrass quality for the majority of the study period. Weed populations were kept below 20% for the two treatments using herbicides. Weeds were highest in the mowing only program, followed by the organic management program, which saw substantial weed encroachment in 2017. This finding highlighted that weed encroachment cannot be managed by maintaining adequate fertility alone at this site.
Environmental hazard analysis
The Environmental Impact Quotient (EIQ) and Hazard Quotient are two formulas using toxological data to provide quasi-quantitative estimates of the environmental and health impacts of applied pesticides. These indices don’t provide a full risk assessment because they don’t estimate potential exposure, but they can be useful in comparing the relative environmental and health risks of various turfgrass management programs.
Note that the risk of all products used in this study was deemed acceptable by the USEPA but a lower relative hazard may provide a way of differentiating among product choices. Just as a turfgrass manager may select a product because of low cost and high efficacy against weeds, these pesticide hazard models could also be factored in when making a product selection. In this case, the UW Integrated Turfgrass Management program picked an herbicide known to be effective, comparably priced with other effective products, but had one of the lowest impact quotients and had approximately 5x lower environmental hazard than the City’s management program as determined by the two methods used.
Economic analysis is difficult to conduct precisely because of fluctuating product pricing and, in the case of the City of Stoughton, the outside contractors that are hired to make the applications. For this study, we used a partial budget analysis approach where only the costs of the materials applied were considered. We did not factor in the cost of making the applications (which is substantial), under the assumption that the application costs would be constant. This assumption is compromised by the fact that the City of Stoughton Program made two applications in 2017, where all other applications were once per year. Another factor is that the large volume of the organic fertilizer required to reach the nitrogen target would likely substantially increase the application costs.
The cost per acre was the highest for the Organic Program, as a result of the relatively high cost of the organic fertilizers used. The City’s Program was less than half of the cost of the Organic Program, and used fertilizers with 100% quick release nitrogen in 2015 and 66% quick release nitrogen in 2017. The UW’s Integrated Turf Program used fewer pesticides than the City’s Program, a higher percentage of slow release nitrogen, but the products cost approximately 50% more than what the City Program used. The UW Program was $60 per acre cheaper than the Organic Program.
This demonstration tracked the agronomic, environmental, and economic performance of four turfgrass management programs at Racetrack Park over a 3-year period. While this was far from a scientific study, the three programs that received inputs of fertilizer were able to maintain acceptable turfgrass quality over the study period. The Organic Program (which mistakenly received an extra fertilizer and herbicide treatment at the initiation of the study) was above reasonable threshold levels for weeds by the middle of 2017. The Organic Program had the greatest cost per acre, followed by the UW Integrated Turfgrass Management Program. The City Program was the lowest cost program of the three with fertilizer inputs, and was less than half of the cost of the Organic Program system. For the two programs where weed control products were used, the UW Integrated Turfgrass Management Program had a 3-5x lower environmental hazard score compared to the City’s Program.
Overall, this demonstration was useful for highlighting that maintaining functional turfgrass can be achieved in different ways. The Organic Program was able to maintain acceptable quality for 3 years, given an initially weed free starting point. After 3 years, weeds are above or approaching most reasonable thresholds. The City of Stoughton Program met turfgrass quality goals and minimized costs; however this program had the highest pesticide hazard scores. The UW Integrated Program used a combination of lower toxicity herbicides and a fertilizer with a high percentage of slow release nitrogen. This system had an intermediate cost relative to the Organic and City programs. We hope that this demonstration will be useful for future conversations about turfgrass management in Stoughton, WI and elsewhere.
WeedMan donated their equipment and labor to make the fertilizer and herbicide applications to field 2 in 2015; Chick Magic donated the fertilizer used on field 1 in 2015; Dow AgroSciences donated the Confront herbicide for field 2 in 2015 and 2017; Bruce Company donated their equipment and labor to make the fertilizer and herbicide applications to field 2 in 2017; and Milorganite donated the fertilizer used on field 1 in 2017.
Doug Soldat is Professor/UW-Extension Specialist, Dept. of Soil Science, UW-Madison; Paul Koch is Assistant Professor/UW-Extension Specialist, Dept. of Plant Pathology, UW-Madison; Chris Williamson is Professor/UW-Extension Specialist, Dept. of Entomology, UW-Madison; Kurt Hockemeyer is Turfgrass Diagnostic Lab Manager, Dept. of Plant Pathology, UW-Madison; and Nick Bero is Research Specialist, Dept. of Soil Science, UW-Madison.