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  • Author or Editor: Dana Sullivan x
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Lawns must be managed increasingly under less frequent or deficit irrigation. Deficit irrigation can reduce gas exchange, carbon assimilation, and physiological function in both warm- (C4) and cool- (C3) season turfgrasses, yet limited research has compared the physiological response to increasing levels of soil water deficit. The objectives of this greenhouse study were to compare three commonly used transition-zone turfgrasses—bermudagrass [Cynodon dactylon (L.) Pers.] (C4), buffalograss [Buchloe dactyloides (Nutt.) Engelm.] (C4), and tall fescue (Festuca arundinacea Schreb.) (C3)—and their ability to maintain quality and physiological function under water deficit stress. Visual turf quality, normalized difference vegetation index (NDVI), reflective canopy temperature, and gross photosynthesis were evaluated initially near field capacity (FC), and subsequent soil water deficit [48% (moderate) and 33% (severe) of plant-available water] conditions. Bermudagrass and tall fescue had similar quality ratings near FC, although the photosynthetic rate was greater for bermudagrass. Compared with other turfgrasses, bermudagrass maintained greater turf quality, NDVI, and photosynthetic rates further into water deficit stress. Tall fescue quality and photosynthetic rates declined most rapidly in both experiments as a result of the combined heat and drought stress. Buffalograss used less water compared with other species, and maintained consistent turf quality, NDVI, and photosynthetic rates under moderate and severe water deficit. These results support the notion that buffalograss and bermudagrass are better adapted than tall fescue at maintaining functional and ecosystem services with shallow soil depths in landscape situations under imposed summertime water restrictions.

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Hybrid bermudagrasses (Cynodon dactylon × C. transvaalensis) typically have excellent wear tolerance when compared with other turfgrass species. This trait should be evaluated during variety development to reduce the risk of failure when new grasses are planted in areas with traffic stress. The objective of this research was to evaluate the wear tolerance of four hybrid bermudagrasses with differing morphological characteristics. Traffic was applied to the hybrid bermudagrass varieties ‘Tifway’, ‘TifSport’, and ‘TifTuf’, as well as an experimental hybrids (04-76) using a traffic simulator for 6 weeks. Leaf morphology (leaf width, length, and angle) and quantitative measure of density and color [normalized difference vegetation index ratio (NDVI), dark green color index (DGCI), and percent green turf color] were characterized before traffic, and then percent green turf color after 6 weeks of traffic was measured to estimate wear tolerance. ‘TifTuf’ hybrid bermudagrass provided the greatest wear tolerance, as well as the narrowest and shortest leaf lengths, greatest NDVI values and percent green color, and lowest DGCI before traffic. Conversely, 04-76 produced the poorest wear tolerance, as well as the widest and longest leaves, lowest NDVI values and percent green color, and highest DGCI values before traffic. Regression analysis determined that DGCI, leaf length, and leaf width were inversely, or negatively, correlated to wear tolerance, whereas percent green turf color before traffic was directly correlated to wear tolerance. For these hybrids, DGCI had the strongest correlation to increased wear tolerance.

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Quantitative spectral reflectance data have the potential to improve the evaluation of turfgrasses in variety trials when management practices are factors in the testing of turf aesthetics and functionality. However, the practical application of this methodology has not been well developed. The objectives of this research were 1) to establish a relationship between spectral reflectance and turfgrass quality (TQ) and percent green cover (PGC) using selected reference plots; 2) to compare aesthetic performance (TQ, PGC, and vegetation indices) and functional performance (surface firmness); and 3) to evaluate lignin content as an alternate means to predict surface firmness in turfgrass variety trials of hybrid bermudagrass [Cynodon dactylon × C. transvaalensis]. A field study was conducted on mature stands of three varieties (‘TifTuf’, ‘TifSport’, and ‘Tifway’) and two experimental lines (04-47 and 04-76) at two mowing heights (0.5 and 1.5 inch) and trinexapac-ethyl application (0.15 kg·ha−1 and nontreated control) treatments. Aesthetic performance was estimated by vegetation indices, spectral reflectance, visual TQ, and PGC. The functional performance of each variety/line was measured through surface firmness and fiber analysis. Regression analyses were similar when using only reference plots or all the plots to determine the relationship between individual aesthetic characteristics. Experimental line 04-47 had lower density in Apr. 2010, whereas varieties ‘TifTuf’, ‘TifSport’, and ‘Tifway’ were in the top statistical group for aesthetic performance when differences were found. ‘TifSport’ and ‘Tifway’ produced the firmest surfaces, followed by ‘TifTuf’, and finally 04-76 and 04-47, which provided the least firm surface. Results of leaf fiber analysis were not correlated with turf surface firmness. This study indicates that incorporating quantitative measures of spectral reflectance could reduce time and improve precision of data collection as long as reference plots with adequate range of green cover are present in the trials.

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