| Use of the plant growth regulator--trinexapac-ethyl--on high maintenance turf areas may function to reduce energy inputs, while enhancing turfgrass performance. Trinexapac-ethyl (TE) offers the potential benefits of reduced mowing frequency, increased rooting, increased tiller density, increased traffic tolerance, reduced fertilizer inputs and reduced water requirements, all without reductions in turfgrass quality. In an attempt to quantify these potential benefits, two field experiments and three greenhouse experiments were conducted from 1995 to 1997 at Colorado State University in Fort Collins, Colorado. The objectives of the first field experiment were to determine the effects of TE, traffic, and nitrogen on Kentucky bluegrass clipping production, root mass, tiller density, quality, and color. The main objective of the second field experiment was to determine the effects of TE on evapotranspiration (ET) rate. The objectives of the three greenhouse experiments were to determine the effects of TE on mesophyll cell density, chlorophyll concentration, structural carbohydrate concentration, and rhizome growth. A label-recommended rate of 0.27 kg TE ha{dollar}sp{lcub}-1{rcub}{dollar} was used in all experiments. Irrigation was applied at 100% of Penman-Monteith reference grass ET every three days in the field. Clipping production was reduced by an average of 57% over four weeks by summer applications of TE, while late spring applications reduced clipping production by only 15%. Root mass was not affected by TE. Tiller density was increased by TE, whether the turf was subjected to traffic or not. The quality and color of turfgrass not subjected to traffic was not affected by TE, while a decrease in quality was observed at the end of 1997 for turfs treated with TE and traffic. All turfs required only 0.49 kg N ha{dollar}sp{lcub}-1{rcub}{dollar} yr{dollar}sp{lcub}-1{rcub}{dollar} to maintain acceptable quality. Three years of lysimeter data failed to detect any difference in Kentucky bluegrass ET-rate due to TE. Mesophyll cell density and chlorophyll concentration were increased, while structural carbohydrates and rhizome growth were unaffected by TE-treatment. Our results indicate that TE may be used to reduce clipping production and increase tiller density while maintaining a high quality Kentucky bluegrass turf under moderate traffic pressure. |
