Turfgrass in an ever-changing world

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2023-05
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Gould, Thomas Michael
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Thoms, Adam W
McDaniel, Marshall D
Christians, Nick E
Thompson, Grant
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Horticulture
Abstract
Turfgrasses are estimated to cover 2% of the United States land area, it is important to ensure lawns are sustainable while still maintaining ecosystem services (Robbins and Birkenholtz, 2003). Previous research has evaluated the sustainability of mixing species and cultivars. Cultivar performance was not accounted for in prior studies. Because of previous work done with biodiversity and ecosystem function theory, it was hypothesized that more genetic diversity would result in less inorganic nitrate and ammonium leaching (Thompson et al., 2016). Sixteen cultivars were selected from the National Turfgrass Evaluation Program (NTEP) trials based on turfgrass quality, and commercial availability [4 Kentucky bluegrass (Poa pratensis L.; KBG) cultivars, 4 tall fescue (Schedonorus arundinaceus (Schreb.); TF) cultivars, 4 fine fescue (Festuca spp.; FF) cultivars, and 4 perennial ryegrass (Lolium perenne L.; PR) cultivars]. Cultivars were grouped into various assemblage types (monocultures, 3-species mixes, 3-cultivar blends, and 3-species by 3-cultivar mixes). Turfgrass assemblages were all similar in drought tolerance, soil organic carbon and soil microbial biomass. Three cultivar assemblages exhibited higher percent green cover from 42-days after seeding until the end of establishment. Three species and three cultivar assemblages leached similar or lower nitrate than 3-species by 3-cultivar assemblages and monocultures. Additionally, athletic field managers often face periods of unplanned suspension from maintenance activities. These suspensions can be due to a variety of reasons including natural disasters, budgetary concerns, or pandemics as recently seen with COVID-19. When turfgrass managers return, turf height-of-cut (HOC) can be much greater than desired. Research was conducted on mature ‘Moonlight’ Kentucky bluegrass grown on a native soil. Turfgrass was left unmaintained from the beginning of the growing season through the end of May. Treatments were subjected to various maintenance regimes including combinations of three different mowing treatments (⅓ rule, cut in half and then ⅓ rule, and scalp to final HOC of 5.1cm), two fertility programs (36.6 kg N ha-1 and 73.2 kg N ha-1) and were either subjected to Trinexapac-ethyl (TE) applications or not. Twenty-five simulated traffic events (STEs) were applied with a modified Baldree Traffic Simulator. Simulated traffic occurred in the fall of 2020 and 2021. Digital images for percent green cover, surface hardness, and rotational resistance were tested after every five STEs. While there are differences in the slope, for the loss of percent green cover, treatment differences were lacking. Orthogonal contrasts determined no differences between regime variables in percent green cover. After 25 STEs, small treatment differences were observed for rotational resistance and surface hardness. Although these differences were very minor between treatments. No hardness measurements were greater than 100 GMAX. Soil bulk density at a 10.2 cm depth was not different between any treatments after 25 STEs. The minimum of a 2-month delay after achieving desired HOC before applying STEs may have allowed the turfgrass to acclimate and thus not result in STE stress to the degree that might be expected if simulated traffic occurred sooner after the desired HOC was reached. There is a need in the turfgrass industry to challenge and update long-standing rules about management practices and decisions. In the case of these two studies, differing societal circumstances and improved varieties of modern day don’t require vastly different changes in management practices.
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