Golf Course Management

JUN 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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06.19 GOLF COURSE MANAGEMENT 69 cover never dropped below 70% for any of the treatments (including the control). e differences in green cover among treatments were relatively small, ranging from 4% to 15%. Although these differences are statisti- cally significant, they may be less important to the turf manager than turf quality differences among treatments. Dark green color index With the exception of plots irrigated at 50% ETos in 2015, bermuda- grass receiving trinexapac-ethyl, either in combination with Revolution or alone, exhibited darker green color when compared with untreated controls at all irrigation levels throughout the research period (Figure 2). Plots treated with Revolution alone did not differ in color from control plots on seven of nine sampling dates (Figure 2). Even though chemical treatments were made until October, dark green color index declined from September to October and November for all treatments. Such a loss in green color can be attributed to the be - ginning of winter dormancy. Turfgrass quality Plots receiving trinexapac-ethyl (alone or in combination with Revo- lution) exhibited better visual turf quality than the untreated controls at 50% ETos in 2014 and 2016, and at 65% and 85% ETos in 2014, 2015 and 2016 (Figure 3). e application of Revolution alone increased turf- grass quality at 50% ETos in 2014, at 50% and 80% ETos in 2015, and at all three irrigation levels in 2016. During the three years of the study, untreated control plots only showed an acceptable visual quality rating of 6 when irrigated at 80% ETos (Figure 4). With the exception of plots treated with trinexapac-ethyl and trinexapac-ethyl + Revolution and ir- rigated at 50% ETos in 2015, all plots receiving chemical applications were given acceptable ratings of 6 or higher during the three years for all irrigation treatments (Figure 3). At 50% ETos, plots treated with any of the three chemical treatments had greater quality than control plots from July to September, with qual- ity ratings of 6 or greater from June to August (Figure 4). e combina- tion of Revolution and trinexapac-ethyl resulted in mean quality ratings of 7.2 in July, 6.7 in August and 6.2 in September. Average ratings of plots treated with trinexapac-ethyl alone and irrigated at 50% ETos were 7.4 in July and 6.0 in August (Figure 4). 9 8 7 6 5 4 3 2 1 9 8 7 6 5 4 3 2 1 9 8 7 6 5 4 3 2 1 Control TE Surfactant Surfactant + TE Quality Quality Quality June July Aug Sept Oct Nov 50% ETos 65% ETos 80% ETos LSD=0.9 LSD=0.8 LSD=0.7 Figure 4. Turfgrass visual quality of Princess 77 bermudagrass treated either with trinexapac-ethyl (TE), Revolution (Surfactant) or a combination of both products and irrigated at either 50%, 65% or 85% ETos from June to November. Values represent an average of 15 data points and are pooled across three years (2014, 2015 and 2016) and five replicates. Overview of the block area irrigated at 50% ETos during summer, showing some of the treatments that exhibit signs of drought but are otherwise relatively healthy. Visual quality over ET levels

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