By Weston Floyd, CSFM, Megan Muesse, Hailey Tucker, Opeyemi Alabi, Jacob Winger, and Chase Straw, Ph.D., Department of Soil and Crop Sciences, Texas A&M University
The demand for precise input application and operational efficiency in turfgrass has driven the development of Global Navigation Satellite System (GNSS)-equipped sprayers, which offer several advantages over conventional systems. Features such as individual nozzle control and automated operation within preset boundaries reduce the need for manual boom control, while enhancements such as sub-centimeter precision correction and autosteer further minimize human error.
Despite these benefits, GNSS sprayers have seen limited adoption in the broader turfgrass industry, with increased interest primarily in the golf course sector. Early adopters report benefits such as reduced treated area, shorter application times, less reliance on operator expertise, and improved accuracy. However, testimonials remain scarce in sports field management, where skepticism about the technology’s value persists.
As the sports field management industry increasingly embraces sustainable practices and faces rising labor costs, the demand for technological solutions is expected to grow. Overcoming hesitancy toward new technologies will require extensive demonstrations to promote adoption. Currently, there is limited unbiased data on the benefits of GNSS-equipped sprayers for sports field managers.
This research aims to fill that gap by quantifying application errors on sports fields using different sprayer technologies and operator experience levels. The hypothesis is that as technology advances, discrepancies in misses, overlaps and overspray will decrease, reducing the total sprayed area and minimizing differences between experienced and inexperienced operators.
Study design, equipment and application process
Research was conducted from winter 2022 to summer 2023 in College Station, Texas, at Veterans Park and Athletic Complex and Southwood Athletic Park. Identical studies were performed on softball/baseball and soccer fields at both locations. Using a crossover design, six treatments – manual, GNSS, and GNSS + autosteer sprayer technologies, each operated by both experienced and inexperienced operators – were applied to three fields of each type at both locations. Each field received all six treatments to evaluate technology performance across operator skill levels.
At Veterans Park, a Toro Workman 200 Spray System (18-foot boom) with Ninja GPS Spray Control, a Smart7 GNSS receiver, and Polaris autosteer was used (Figure 1 above). At Southwood Athletic Park, a John Deere ProGator with an Above Par Tech sprayer (20-foot boom), a GPS 7500 GNSS receiver, and SteadySteer autosteer was employed (Figure 2). Both sprayers featured correctional services, individual nozzle control, automatic rate control, on-screen guidance and adjustable spray parameters.
One experienced operator with nearly 20 years of sports field spraying experience, including three years with GNSS and autosteer, was assigned to each location. Four inexperienced college students – new to both spraying and the technology – were assigned to specific locations and field types, ensuring their inexperience remained consistent. Each student received a 30-minute training session on sprayer controls before their first application.
Field boundaries were georeferenced once using the sprayers’ GNSS receivers to establish consistent target areas for all fields, aiding in GNSS and GNSS + autosteer treatments. The average target areas were 74,899 ft² for Veterans Park’s softball fields and 37,631 ft² for Southwood Athletic Park’s baseball fields, with soccer fields averaging 88,244 ft² and 33,644 ft² at Veterans and Southwood, respectively. Water was used for treatments at 65 gallons per acre, and designated level areas were marked for filling and draining the sprayers. Sprayers were filled to 150 gallons for Veterans and 80 gallons for Southwood, based on field size.
At Veterans Park, the dual-nozzle sprayer used FastCap 422FC11004 and 422FC11006 nozzles, while Southwood Athletic Park used a single-nozzle sprayer with COMBO-JET SR110-08 nozzles. The accuracy of the water volume in the tank was confirmed by measuring in five-gallon increments and validating the flow meters against the computer outputs before the initial treatments.
Treatment applications occurred from December 2022 to May 2023 at Veterans Park and from June to July 2023 at Southwood Athletic Park, depending on field availability and weather. To prevent tire tracks from being used as a guide, sufficient time was allowed between applications for the tracks to disappear. Sprayers operated at 2.5 mph, controlled by a speed regulator.
For manual treatments, monitors were covered, and foam markers guided operators, who manually controlled the booms. GNSS treatments used foam markers and on-screen maps, while GNSS + autosteer treatments added autosteer. Both GNSS treatments featured individual nozzle control, with a 100% overlap setting. After each treatment, remaining water was drained via valve and hand pump. Spray data were stored in the sprayers’ computers and later exported for analysis.
Data processing and analysis
The study measured target area misses, overlaps and overspray. Data downloaded from the sprayer computers included field boundaries, sprayer paths and coverage. The percentage of target area missed and overlapped was calculated by comparing the spray coverage to the field boundaries, excluding non-target areas. Missed areas were identified where no spray was applied, and overlaps where sections were sprayed more than once. These percentages were then calculated as a proportion of the total target area. Overspray was calculated by subtracting the amount of water left in the tank after spraying from the initial volume. The percentage of overspray was determined by dividing the actual volume applied by the intended volume for the target area, then multiplying by 100. Any values over 100% indicated overspray.
The percent total volume saved between treatments was determined by subtracting the lower percentage from the higher one, dividing the absolute value of this difference by the higher percentage, and then multiplying by 100 to convert it into a percentage. For example, if treatment A used 105% of the intended volume (i.e., 5% overspray) and treatment B used 110% of the intended volume (i.e., 10% overspray), then the total volume savings by using treatment A is 4.6%, calculated as ((|105-110|)/110)*100 = 4.6%.
Only the 422FC11004 nozzles were used at Veterans Park in manual mode because individual nozzle control could not be turned off when dual nozzles were active – resulting in a lower spray volume since the sprayer isn’t designed for single-nozzle operation. Therefore, the percent target area overspray was analyzed separately by location, as the manual total volume applied data from Veterans Park was unreliable. However, this issue did not affect the percent of the target area missed and overlapped, as spatial spray data were recorded for all treatments.
Misses, overlaps and overspray on softball/baseball fields
The results for percent target area missed were similar across locations, so data were combined for treatments and locations. Inexperienced operators using manual sprayers had the highest percentage of missed areas (3.7%), while experienced operators showed no major differences across sprayer technologies. There was also no difference in missed areas between GNSS and GNSS + autosteer, regardless of operator experience. Southwood Athletic Park had more missed areas (2.4%) compared to Veterans Park (1.4%).
For percent target area overlapped, results differed by location, so data are presented separately for each. At Veterans Park, the manual sprayer used by inexperienced operators caused the highest overlap (8.3%). In other cases, both experienced and inexperienced operators performed similarly across sprayer technologies. As technology advanced, overlap decreased, with GNSS + autosteer reducing overlap to less than 2% (Figure 3).
At Veterans Park, overspray was similar between operators within each technology level, but advanced technology reduced overspray. GNSS + autosteer led to 2.1% overspray compared to 6.3% with GNSS, saving 4% of the total water volume. For inexperienced operators, autosteer reduced overspray by 3.3%.
At Southwood Athletic Park, there were no significant differences in overspray between operators within each technology level, but experienced operators generally had higher overspray. While there wasn’t a clear advantage between manual and GNSS or GNSS and GNSS + autosteer, switching from manual to GNSS + autosteer significantly reduced overspray. For experienced operators, overspray dropped from 11.5% with manual to 6.5%; and for inexperienced operators, it dropped from 9.7% to 5.7%, resulting in a 3.7% reduction in total water used.
Misses, overlaps and overspray on soccer fields
The results for percent target area missed on soccer fields were consistent across locations, so data were combined for treatment analysis. The manual inexperienced operator had the highest percentage of missed target area (2.8%), which was higher than all other treatments. There were no differences in missed areas among experienced operators across any level of sprayer technology. Additionally, there was no difference in missed areas between GNSS and GNSS + autosteer, regardless of operator experience.
Similarly, the results for percent target area overlapped were consistent across locations, so data were pooled for analysis. The manual inexperienced operator had the highest overlap (6.4%), significantly more than the manual experienced operator (4.3%). The manual experienced operator’s overlap was similar to that of the GNSS inexperienced operator (3.6%), and both operator types showed similar results within the GNSS and GNSS + autosteer technologies. Overlap decreased as sprayer technology advanced, with both operator types achieving less than 1% overlap using GNSS + autosteer (Figure 4).
The results for percent target area oversprayed differed slightly between locations, so data are presented separately. At Veterans Park, operator experience did not affect overspray with the GNSS sprayer, with both experienced and inexperienced operators having similar overspray rates (6.2% and 6.5%, respectively). However, the addition of autosteer reduced overspray to 2.3% for experienced operators and 3.8% for inexperienced operators, resulting in total water savings of 3.7% and 2.5%, respectively.
At Southwood Athletic Park, overspray results were similar between operators within each sprayer technology level, though the inexperienced operator consistently had slightly higher overspray. For experienced operators, overspray decreased from 11.1% with manual to 8.3% with GNSS, but there was no further reduction with GNSS + autosteer (6.2%). For inexperienced operators, overspray dropped from 12.1% with manual to 10.2% with GNSS and further to 7.0% with GNSS + autosteer.
Overall, both operator types saw a reduction in overspray as sprayer technology advanced. Moving from manual to GNSS technology reduced overspray by 2.8% for experienced operators and 1.9% for inexperienced operators. Upgrading from GNSS to GNSS + autosteer reduced overspray by 2.1% for experienced operators and 3.2% for inexperienced operators. Switching from manual to GNSS + autosteer technology resulted in total water savings of 4.4% for experienced operators and 4.6% for inexperienced operators.
Recommendation for sports field managers
Inexperienced operators using manual spray mode had the highest rates of misses and overlaps, except for overlaps on Southwood Athletic Park’s baseball fields. GNSS and autosteer technologies significantly reduced these errors across all locations and field types (Figure 5). Standard deviations of misses and overlaps decreased with advanced technologies, especially when comparing inexperienced manual mode to GNSS + autosteer, indicating more consistent applications. Additionally, advanced technology reduced overspray and the total volume applied. Investing in GNSS-equipped sprayers with autosteer minimizes reliance on experienced operators, reduces errors and enhances consistency. This study used factory settings, so further improvements might be possible by adjusting overlap parameters.
Acknowledgements
The authors wish to extend their gratitude to the Texas Turfgrass, Research, Education and Extension Endowment for providing funding for this study. They also want to express their thanks to GLK Turf Solutions and Traqnology for providing the Above Par Tech sprayer and real-time kinematic correction service, respectively, for use in the study. Additionally, appreciation goes to Stephan Richardson, parks operations manager of the City of College Station; Curtis Richmond, Southwood Park supervisor; Keith Fails, Veterans Park supervisor; and Ken Rost and Cam Schafer from Frost, Inc. for their support of this project.
