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  • Author or Editor: Filippo Rimi x
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In transitional environments, turf managers and sod producers of warm-season grasses face the issue of winter annual weeds that can dominate dormant turf stands through the winter until late spring. The use of glyphosate to control weeds in dormant bermudagrass (Cynodon dactylon) has been well documented, but information is lacking about its effect on spring green-up of other warm-season grasses. A field study was conducted on two commercial sod farms in northern Italy (Expt. 1) to evaluate the effects of glyphosate applied on two different winter dates on weed control and spring green-up of ‘Zeon’ manilagrass (Zoysia matrella). A second study was carried out at the experimental agricultural farm of Padova University (Expt. 2) to assess the effects of a winter application of glyphosate on weed control and spring green-up of ‘Yukon’ bermudagrass and ‘Companion’ zoysiagrass (Zoysia japonica). Each experiment was conducted from Jan. to June 2011, and glyphosate was applied at 1.1 kg·ha−1 on 8 and 21 Feb. in Expt. 1 and on 8 Feb. in Expt. 2. Spring recovery was evaluated by periodical visual ratings of green turf cover and by collecting normalized difference vegetation indices (NDVIs). Weed injury was visually evaluated on all plots 7 weeks after the 8 Feb. glyphosate application. The visual ratings of green cover were strongly and positively correlated with NDVI measurements. Glyphosate applied in February as a single treatment effectively controlled winter weeds in ‘Zeon’ manilagrass (Expt. 1) and ‘Yukon’ bermudagrass (Expt. 2) without negatively affecting spring green-up. In contrast, spring green-up of ‘Companion’ zoysiagrass (Expt. 2) was delayed by the application of glyphosate.

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Bermudagrass is the most widely used warm-season turf species in the transition zones of Europe. The Venetian valley (northeastern Italy) is a typical transitional zone, characterized by cold winters and hot summers, where the performance of bermudagrass mostly depends on cold tolerance and duration of winter dormancy. A 2-year field study was conducted from May 2009 to July 2011 at the agricultural experimental farm of Padova University. The objective of this study was to assess the relationships occurring between spring green-up of seeded bermudagrasses and their nonstructural carbohydrates and crude protein (CP) content in stolons during late winter. The cultivars used were ‘Caribe’, ‘Mohawk’, ‘Princess-77’, ‘Sultan’, ‘SWI 1012’, and ‘Jackpot’. The plots were seeded in May 2009 and turf samples were collected in Mar. 2010 and 2011 for determination of stolons dry weight, diameter, and content of carbohydrates and CP. ‘Princess-77’ had lower content of starch in stolons compared with the other cultivars and was characterized by late spring green-up. The cultivars tested showed wide differences in stolons morphology (dry weight and diameter), whereas there were poor diversity for CP and water-soluble carbohydrates (WSC) in both years of research. Correlation analyses indicated a negative relationship between the days of the year necessary for spring green-up and stolons starch content and also between CP and starch. Moreover, there was a positive correlation between stolons starch and diameter, suggesting that spring green-up may be enhanced by selection of high starch-accumulating cultivars having coarse stolons.

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Winter dormancy is the main impediment to a wide acceptance of warm-season turfgrasses in the Mediterranean countries of Europe due to a loss of color during the winter months. Scalping during late winter or early spring has been recommended anecdotally to enhance spring green-up of bermudagrass (Cynodon dactylon); however, information is lacking on the effectiveness of this practice. A study was conducted to investigate the effects of spring scalping on spring green-up of eight bermudagrass cultivars (Barbados, Contessa, La Paloma, Mohawk, NuMex Sahara, Princess-77, SR 9554, and Yukon) grown in a transition zone environment. The trial was carried out in Spring of 2009 and 2010 on plots established in July 2005 at the experimental farm of the University of Padova (northeastern Italy). Half of the plots for each cultivar were subjected to spring scalping, which was applied in both years on 13 Mar. with a rotary mower set at a height of 28 mm. Soil temperatures were recorded hourly during the research period at a depth of 2.5 cm. The percentage of green cover was estimated weekly from 0 to 98 days after spring scalping (DASS). Soil temperatures in scalped plots were greater than in unscalped plots. Among the cultivars tested, ‘Yukon’ showed earliest spring green-up, with no difference between the scalping treatments, reaching 80% green cover by the end of April. For all other cultivars, scalped plots reached 80% green cover 10 to 18 days earlier than unscalped plots. Results showed that scalping enhanced spring green-up, primarily for cultivars that recover slowly from winter dormancy.

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