The Fertilizer and Mowing Recipe for Community-Level Sports Fields
By Brynn Johnson & Tyler Carr, Ph.D.
Sports field managers face the problem of having little to no control over the amount of traffic applied to their fields. Because of this, we need to better define primary cultural practices to maximize their limited resources. Of the primary cultural practices, mowing and fertilization are easier to manage since facilities might have limited access to irrigation, which can be directly related to these other areas. Mowing height can be adjusted based on how often a sports field manager/crew is able to mow. Fertilization rate can be based on what other resources (money, time, staff, etc.) are available. These areas need to be optimized to increase the longevity of a sports field by prolonging turfgrass coverage under traffic.
Separate research projects are being conducted on Kentucky bluegrass (the most commonly used turfgrass for sports fields in Ohio) and tall fescue (a lower-input option). Within each species, plots are mowed three times per week (1.5 inches), two times per week (2.5 inches), or once per week (3.5 inches) with a rotary push mower. Within each mowing height trial, there are six nitrogen rates applied ranging from 0-5 lb N/1000 ft2 (Figure 1). Ten applications of fertilizer occurred every two weeks with ammonium sulfate (21-0-0).
Halfway through the fertilization applications, in August, the traffic program was initiated. This simulated traffic is applied with a Baldree Traffic Simulator (modified Toro Procore 648). Instead of aeration tines there are metal feet which replicate cleats. One game of traffic is equivalent to one game of traffic on a professional or intercollegiate football field at the 40-yard line between the hash marks. Thirty-three games of traffic are applied over eleven weeks. Three games were applied per week sequentially to simulate a football practice field.
Green turfgrass coverage was collected using digital image analysis, which collects a photo of the turfgrass under controlled lighting conditions (Figure 2). This metric is assessed by the number of green pixels relative to the total number of pixels in the photo. Rotational resistance, surface hardness, visual quality, and soil moisture/temperature were also collected. The first-year data collection from 2024 resulted in no significant difference in coverage between 3 and 5 lb N/1000 ft2 on tall fescue. On Kentucky bluegrass and tall fescue, the 3.5 inch mowing height had lower green turfgrass coverage than 1.5 inches, demonstrating that lower mowing heights improved traffic tolerance. This experiment will be repeated in 2025, with mowing and fertilization programs beginning in June.
