Growth and Evapotranspiration Response of Two Turfgrass Species to Nitrogen and Trinexapac-ethyl

Abstract

<jats:p>Resolution of the effects of trinexapac-ethyl and nitrogen (N) application rate on evapotranspiration of low-cut, prostrate turfgrass species such as creeping bentgrass (<jats:italic>Agrostis stolonifera</jats:italic> L.) and hybrid bermudagrass [<jats:italic>Cynodon dactylon</jats:italic> (L.) Pers. × <jats:italic>Cynodon transvaalensis</jats:italic> Burtt-Davy] has not been explored. This study sought to examine the integrated growth and evapotranspiration responses of these two turfgrass species to two N rates and application of trinexapac-ethyl, a commonly used growth-regulating compound for suppressing turfgrass shoot growth. ‘Penncross’ creeping bentgrass and ‘Tifdwarf’ bermudagrass were studied. We hypothesized that application of trinexapac-ethyl and/or lower N application rates might result in lower rates of turfgrass evapotranspiration. Two greenhouse studies were conducted over 6-week periods in 2008. A completely randomized design was used to support a two species × two N rate × two trinexapac-ethyl rate factorial. Shoot and root growth and evapotranspiration were determined from the two grass species when maintained in well-watered conditions and grown in pots. The treatments were either a high N (1.2 g N/m<jats:sup>2</jats:sup>/week) or a low N (0.3 g N/m<jats:sup>2</jats:sup>/week) application and either 0 or 28 mg·m<jats:sup>−2</jats:sup> a.i. trinexapac-ethyl. Application of trinexapac-ethyl and use of the low N rate each significantly reduced shoot growth in both species; however, neither factor caused a reduction in turfgrass water use. The high N rate promoted increased root growth in both species during the spring, but there was no effect of either factor on rooting during the summer study. These results indicate that although decreasing N application rates and applying trinexapac-ethyl effectively suppress shoot growth, neither is likely to have any impact on overall water requirements for these species when maintained in well-watered conditions.</jats:p>

Irrigation Water Quality and Trinexapac-ethyl Effects on Bermudagrass Response to Deficit Irrigation

“…The greater relative growth suppression observed during the spring compared with the summer suggests that more rapid metabolism of TE may have occurred with the longer days and higher incident radiation of summer. Decreased summer efficacy of TE has been previously reported in multiple species and is considered a result of more rapid metabolism in the plant (Beasley and Branham, 2007;Kreuser and Soldat, 2011;Lickfeldt et al, 2001;Wherley and Sinclair, 2009). Furthermore, our data showed no significant TE • irrigation level interaction in either study, suggesting that relative levels of growth suppression provided by TE were similar between full-and deficit-irrigated treatments.…”

Turfgrass Benefits and Issues

“…McCann and Huang (2007) showed the currently popular growth retardant trinexapac-ethyl [4-(cyclopropylhydroxymethylene)-3,5-dioxo-, ethyl ester] reduced the ET of creeping bentgrass approximately 0.4 mmol m⁻ 2 s⁻ 1 10 d after application during drought and heat stress, yet increased ET by 2 mm at 21 d after application. In nonstress conditions, trinexapac-ethyl did not aff ect the ET of Kentucky bluegrass, creeping bentgrass, or hybrid bermudagrass (Ervin and Koski, 2001;Wherley and Sinclair, 2009).…”

“…Fertility and mowing aff ect water use rates, although the data do not always agree on their eff ects. In a greenhouse study (Wherley and Sinclair, 2009), low rates of nitrogen (0.3 g m⁻ 2 wk⁻ 1 ) did not reduce the water use of creeping bentgrass (Agrostis stolonifera L.) or hybrid bermudagrass compared with a high nitrogen rate (1.2 g m⁻ 2 wk⁻ 1 nitrogen). The ET rates of Kentucky bluegrass and kikuyugrass (Pennisetum clandestinum Hochst.…”

Effects of Trinexapac‐Ethyl and Daconil Action (Acibenzolar‐S‐Methyl and Chlorothalonil) on Heat and Drought Tolerance of Creeping Bentgrass

“…Another compound that has been widely studied is a plant growth regulator, trinexapac‐ethyl (TE), that acts by inhibiting the phytohormone gibberellic acid by preventing the conversion of the precursor GA 1 to active forms of gibberellins (Rademacher, 2000). This ultimately results in plants having reduced height, increased density, and improved canopy characteristics (McCullough et al, 2007; Wherley and Sinclair, 2009). Furthermore, TE has also been implicated in improving the abiotic stress tolerance of turfgrasses (Heckman et al, 2001; Zhang et al, 2003).…”