AUTUMN NITROGEN (N) AND TRINEXAPAC-ETHYL (TE) APPLICATIONS INFLUENCE SPRING VIGOR AND DENSITY OF C3 PUTTING GREENS

Open Access
Author:
Rogan, Chase Michael Paul
Graduate Program:
Agronomy
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 21, 2011
Committee Members:
  • Maxim J Schlossberg, Thesis Advisor
Keywords:
  • density
  • vigor
  • Trinexapac-ethyl
  • Nitrogen
  • tissue N
Abstract:
ABSTRACT Putting greens across the northern United States and Canada are perennially affected by winter damage, which requires costly spring renovation. This damage ensues from any number of winter stresses, or a complex of combined stresses. Little is known about late autumn conditioning of putting green systems by application of soluble N and trinexapac-ethyl (TE) to achieve maximum plant hardiness, and prevent damage. A field experiment was initiated in Sept. 2009 and 2010 to determine optimal timing of late season N and TE applications, as well as the interactive and/or main effects on tissue N concentrations, spring vigor, and density of an intensively-managed PG within the Pennsylvania State University Valentine Turfgrass Research Center (University Park, PA). The experimental design comprised treatments of N (30 or 60 kg ha–1), trinexapac-ethyl (0, 0.088, or 0.044 + 0.044 kg ha–1), and four autumn application timings; in a completely-randomized, 24-plot arrangement replicated six (2009-2010) or four (2010-2011) times. Resulting turfgrass clipping yield (CY; kg ha–1), tissue N (g kg–1), and canopy density (green normalized differential vegetative index; GNDVI) were measured in March and early-April of 2010 and 2011. Regardless of N rate, N concentrations of post-application (late autumn) clippings were significantly higher on plots treated before the first hard frost, compared to plots treated after the first hard frost. Although plots treated later in the year contained less tissue N prior to winter, these differences were indistinguishable in spring, when tissue N concentrations were similar across all application dates. As one might expect, plots treated with the high N rate showed significantly greater tissue N in both autumn and spring, compared to plots treated with the low N rate. With regard to autumn tissue N, TE was not a significant influence. However, a difference was discerned in spring analysis, as plots previously treated by TE showed significantly greater N concentration in spring tissue. Spring CY decreased linearly over early to late-Fall application dates. Significant treatment interactions were observed for low vs. high N rate, as well as TE treatment. When N and TE were applied in autumn (particularly after the first hard frost), early spring growth was suppressed by residual activity of TE, even when tissue N concentrations were high. Conversely, when applications were discontinued earlier in autumn (before the first hard frost), spring growth was stimulated more so than by application of N alone. This result is likely a manifestation of post-regulation surge, commonly associated with the eventual metabolism of GA-inhibitors in TE. Spring GNDVI readings were directly related to autumn N rate, but a positive effect of either TE application regimen was observed at α = 0.1. Regardless of application date, the high N rate resulted in significantly higher GNDVI readings than the low N rate. As mentioned, application of autumn TE also improved density in spring. Furthermore, the greatest improvement of density is realized when N and TE applications are made prior to the first hard frost, but applications made after the first hard frost also prove worthwhile. In summary, spring PG tissue N, vigor, and density appear positively influenced by Fall inputs of N & TE, particularly when applied up to 15-d prior to the first hard frost. While N applied after the first hard frost still proved beneficial, the 30 kg ha–1 rate was as effective as the 60 kg ha–1 rate. Late fall N fertilizer applications to internally-drained, sand-based putting greens should not exceed 30 kg ha–1. A similar study was initiated in Oct. 2010 at the Pennsylvania State University Joseph Valentine Turfgrass Research Center in University Park, PA. A randomized split-plot design of 90 plots was established on a mature, annual bluegrass putting green. The experimental design comprised paired main plots of Phosphorus treatment or none, each containing treatments of N (0, 30 or 60 kg ha¬¬¬–1), trinexapac-ethyl (TE; 0 or 0.088 kg ha–1), and three autumn application timings, in a completely-randomized, 15-split-plot arrangement. Resulting turfgrass canopy density (green normalized differential vegetative index; GNDVI), tissue N (g kg–1), and clipping yield (CY; kg ha–1) were measured in March and early-April of 2011. The main plot effect of Phosphorus was not a significant source of variation for spring N offtake, tissue N, canopy density, or vigor. Autumn N offtake and tissue N were significantly affected by timing, treatment, and their interaction. Regarding the timing source, cumulative N offtake was greatest from plots treated earliest. The same general trend was observed of mean tissue N in autumn clippings, and was likely due to decreasing temperatures and associated decline in turfgrass assimilation rate. Spring GNDVI and vigor were significantly influenced by N rate, but not TE. While the effect of TE appears to have influenced spring vigor, the TE vs. No TE contrast was not significant at an alpha level of 0.05.