ATA Turf Times – Beth Guertal, Professor, Auburn University and Dave Han, Extension Specialist and Associate Professor, Alabama Extension and Auburn University

New bermudagrasses (both hybrid and improved vegetative selections of common bermudagrass) are being introduced into the turfgrass market, intended for use in athletic fields, home lawns, golf course fairways, and commercial landscaping. The grasses vary in their shade tolerance, resistance to various diseases, color, texture, and ability to tolerate traffic. For bermudgrasses used on athletic fields, traffic tolerance is one of the most important traits. So, in 2017, researchers at Auburn University installed a study to look at long-term traffic tolerance that evaluated six bermudagrass cultivars available commercially at the time under three levels of artificial traffic. This study evaluated the cultivars’ traffic tolerance when used as a typical high school athletic field.

In April of 2017 sod was laid from six different bermudagrass cultivars commonly used for southeastern US athletic fields. Cultivars were: Tifway, TifGrand, TifTuf, Latitude 36, NorthBridge (hybrid) and Celebration (vegetative common). The grasses were all obtained as sod cut from various commercial sod farms, and all sod was laid on the same day. Sod was laid in plots measuring 10 x 20 feet in size, with each main block of ‘cultivar’ replicated four times in a randomized complete block design.

Traffic was applied as strip plots across each cultivar (each traffic strip was 3 feet wide and 10 feet long), imposed using an artificial traffic simulator. Three levels of traffic were applied to the bermudagrasses: none, low (3 American style football games per week) or high (5 American style football games per week) foot traffic. The artificial traffic simulator is an aerification unit with the tines removed and replaced with strips of tire in which bolts are embedded. The traffic simulator is run up and down each plot, with the tires/bolts simulating foot wear and traffic. Traffic was applied during the typical US high school football season, from late August — November of each year (2017, 2018 and 2019). Figure 1 Plots were not overseeded in the winter, and in all other aspects (irrigation, fertilization, pest control) were managed as a higher-quality high school football field. Mowing height was 2 inches, done 3 times a week using a rotary mower, with clippings returned. Plots were not topdressed nor aerified from year to year.

Collected data included monthly color and quality using a relative 1 – 9 scale, with a score of ‘1’ for completely brown or dead turf, and a score of ‘9’ for lush, dark green turf. Additional data included shoot density, dry weight of roots, rhizomes and stolon, clipping yields, and spring density of Poa annua.

The results (to date) have shown that the cultivars do respond differently to different levels of traffic, but this mainly occurred in the fall, when the grasses were being actively trafficked. In the spring, the grasses had no traffic, and all of them tended to recover from the fall traffic, and differences in shoot density were only due to the cultivar itself. Table 1 shows shoot density of the various cultivars in the spring in various years, and only the highest level of traffic ever decreased shoot density. There were differences in cultivar, with TifGrand often having highest shoot density, and Celebration the lowest. In the fall, when traffic was being applied, Tifway and TifGrand were most affected by increasing levels of traffic, with shoot density decreasing from 5.6 to 3.4 shoots per square centimeter as traffic increased. In comparison, trafficked plots of NorthBridge and Celebration tended to not be as affected by traffic. Although their overall shoot density was often less, it did not reduce further when traffic was applied.

Table 1. Shoot density (shoots per square centimeter) of bermudagrass managed as an athle...