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

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Resolution of the effects of trinexapac-ethyl and nitrogen (N) application rate on evapotranspiration of low-cut, prostrate turfgrass species such as creeping bentgrass (Agrostis stolonifera L.) and hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis 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/m2/week) or a low N (0.3 g N/m2/week) application and either 0 or 28 mg·m−2 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.