This spring I have been on sabbatical working on a few different writing projects. I’ll tell you more about them in the future as they are all still a work in progress. I have also been busy working on several papers that will be presented in 2025 at the International Turfgrass Research Society in Japan. I thought I would take a minute to briefly tell you about these papers and highlight a few key findings of each.

Project 1: Allelopathic Potential of Cool-Season Turfgrass Species

(see picture and write-up on next page)

This project focused on allelopathy, which is the ability of one plant to effect another through the production of chemical compounds that escape from their leaves or roots. Essentially, it is the natural ability of grasses to out-compete weeds or inhibit their germination and establishment. The objective of this collaborative, multi-state experiment was to assess the allelopathic potential of common cool-season turfgrass species (Chewings fescue, hard fescue, Kentucky bluegrass, perennial ryegrass, slender creeping red fescue, strong creeping red fescue, and tall fescue) on common turf weeds (annual bluegrass, dandelion, goosegrass, and large crabgrass). Greenhouse and laboratory experiments were conducted to evaluate the effect of turfgrass competition, leaf extracts, and soil leachates on the germination and growth of weed species. In short, we learned that a few things including that most turfgrass species have limited allelopathic affects. Rather than picking a turfgrass species for potential allelopathic effects, these results point to the more effective weed management strategy of maintaining a dense and robust turf sward capable of outcompeting weeds for light, nutrients, and water.

Project 2: Optimizing Proxy (ethephon) Application Timing for Zoysiagrass Seedhead Suppression

Prolific zoysiagrass seedhead production in the spring can increase golf course maintenance costs and reduce the visual appearance of fairways. From previous research, we know we can suppress zoysiagrass seedheads with Proxy but we were uncertain of the optimum application timing. This multi-state experiment aimed to determine the optimum window for an effective Proxy application for ‘Meyer’ zoysiagrass seedhead suppression. Field research was conducted in Indiana, Kansas, Arkansas, and Tennessee. Seedheads were suppressed from 0 to 99% depending on application timing. In Indiana, applications between 30 August and 2 October provided >82% seedhead suppression. In Kansas, the timing was similar and the optimum application timing was about two to three weeks later in AR and TN. Using growing degree days, we were able to create a model to predict the optimum ethephon application timing. This research helped defined an optimum autumn application timing window for spring zoysiagrass seedhead suppression across a broad geographic range.

Project 3: Turfgrass Canopy Shade Effects on Crabgrass Germination

Smooth crabgrass is a summer annual grass and one of the most troublesome weeds in Indiana. Field experiments at the Daniel Turf Center demonstrated a strong relationship between spring photosynthetic active radiation (light) reaching the soil surface and the resulting cover of smooth crabgrass in Kentucky bluegrass in August. Both smooth crabgrass and canopy penetrating light were reduced by higher mowing heights and nitrogen fertilization rates. Based on these field experiments, follow-up experiments in controlled environments to improve our understanding of how light quality and quantity influence smooth crabgrass germination and growth. Overall, experiments indicate that light quality and quantity has no effect on smooth crabgrass germination and that smooth crabgrass can even germinate in the dark. We proved that while smooth crabgrass is able to germinate regardless of turfgrass canopy density, new crabgrass seedlings do not properly grow and develop in dense turfgrass due to shade stress on the crabgrass from the turfgrass plants. As such, the age-old adage, that a good turf is the best defense against weeds, holds true.

Project 4: Turfgrass Species and Turf Age Influence Soil Carbon Accumulation

You have probably heard about carbon sequestration to reduce atmospheric carbon dioxide concentrations, but you may not be aware that turfgrasses are great accumulators of soil carbon. However, little is known about how turfgrass species selection affects carbon sequestration potential or how this varies over time. To learn more about this, we studied carbon accumulation in three turfgrass species over time and soil depths. A total of 25 locations throughout Indiana were sampled from established swards of Kentucky bluegrass, tall fescue, and zoysiagrass. Turfgrass species affected soil carbon concentrations but had no effect on soil total nitrogen. As turfgrass areas age, total soil carbon, total soil nitrogen, and organic matter increased near the soil surface (0-to-3-inch depth) but little a 3-inch depth. Learning more about how turfgrass species accumulate soil carbon and nitrogen will aid in our understanding of how to modify their management overtime as these areas age.