Mowing effects on highway right-of-way. A vegetation height of greater than 30 centimeters on a highway right-of-way is generally considered a safety hazard to drivers. How often and at what height should the right-of-way be mowed in order to maintain a safe environment?
This was the question of interest in an article published in the Landscape Ecology Journal (Jan.
2013). The researchers designed an experiment to estimate the effects of mowing frequency and mowing height on the mean height of vegetation in the highway right-of-way. Mowing frequency was set at three levels: LO4 once, twice, or three times per year. Mowing height of the equipment was also set at three levels: 5, 10, or 20 centimeters. A sample of 36 plots of land along a highway right-of-way were selected, and each was randomly assigned to receive one of the 3 * 3 = 9 mowing frequency/
mowing height treatments. The design was balanced so that each treatment was applied to 4 plots of land. At the end of the year, the vegetation height (in centimeters) was measured for each plot. Simulated data are shown in the table. Conduct a complete analysis of variance of the data. What inferences can you make about the effects of mowing frequency and mowing height on vegetation height?
Mow Height Mow Frequency Vegetation Height (cm)
5 1 19.3, 17.3, 15.0, 16.7 10 1 16.0, 15.6, 16.9, 15.0 20 1 16.7, 17.9, 15.9, 13.7 5 2 22.4, 20.8, 24.5, 21.7 10 2 23.9, 23.6, 21.7, 23.8 20 2 24.7, 26.3, 27.2, 26.4 5 3 18.6, 17.9, 16.1, 19.4 10 3 22.2, 25.6, 21.8, 23.6 20 3 27.0, 25.3, 23.8, 28.0