Larry G. Steward, Assistant Professor of Horticultural Industries Technologies, Agricultural Technical Institute, The Ohio State University, Wooster, Ohio; T.Davis Sydnor, Professor of Urban Forestry, School of Natural Resources, The Ohio State University, Columbus, Ohio; and Bert Bishop, Senior Statistician, Computing and Statistical Services, Ohio Agricultural and Research and Development Center, The Ohio State University, Wooster, Ohio.
Cigarette Trials
Averaging the two cigarette trials, cigarettes discarded on the mulch surface ignited composted yard wastes and ground recycled pallets more often than ground rubber, pine straw, shredded hardwood, 1/2-inch pine bark nuggets, cocoa shells, and brick chip mulches and bluegrass sod (Table 1).
Oat straw, shredded cypress bark, 1/2- to 1-inch pine bark nuggets, and shredded pine bark ignited infrequently enough that they were not statistically different than those that never ignited (Table 1). Interestingly, oat straw only ignited during the first trial, while shredded cypress bark, recycled yard wastes, and shredded pine bark only ignited after being in the landscape for six months (data not shown).
| Table 1. The Number of Times That Specific Mulch Types Ignited After Three Cigarettes Were Discarded on the Surface of the Mulch. Each Trial Was Conducted Twice on Each of the Four Replicates. | |
| Mulching Material | Times Ignition Occurredz |
| Ground recycled pallets | 4y |
| Composted yard waste | 4y |
| Shredded pine bark | 3 |
| Oat straw | 2 |
| Shredded cypress bark | 2 |
| Pine bark nuggets (1/2 to 1-inch) | 1 |
| Decorative ground rubber | 0 |
| Pine straw (needles) | 0 |
| Shredded hardwood bark | 0 |
| Pine bark nuggets (1 to 2-inch) | 0 |
| Cocoa shells | 0 |
| Bluegrass sod | 0 |
| Brick chips | 0 |
|
z Ignition of each mulch was attempted eight times (2
trials x 4 replicates) using lighted cigarettes. y Mulches that ignited four times (typically after aging or during the second test) out of eight attempts, were different, at the 0.05 level of significance, from mulches that never ignited using the Fisher's Exact Test. Logistic regression showed no differences between mulches that sometimes ignited. |
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Further, the type of cigarette affected the ignition. Three different types of cigarettes were used on each replication, and highly filtered cigarettes generally burned out before igniting the mulch. Unfiltered cigarettes were generally the cause of ignition when the mulch ignited.