2018 ASHS Annual Conference

Aged pine bark is the one of the most common organic substrate components in the U.S., with bark from loblolly or longleaf pines being the most prominent in the southeastern U.S. Aging is a process in which the bark is piled on the ground in windrows and allowed to age for a period of time, usually six months to one year. Aging time can vary between suppliers, or even for the same supplier, based on factors such as space shortages, product demand, or preference. A long-term study was implemented to quantify the changes that occur in temperature profiles in longleaf pine bark windrows over the course of twelve months of aging. Temperature profiles during the aging process are characterized by (1) a rapid initial increase in temperature, (2) a sustained high-temperature period, and (3) a decline to near-ambient temperatures. Pile temperatures were measured on the research site at each month for twelve months. Measurements were taken at three different heights at depths of 1, 2, 3, and 4 ft. using three 4 ft. compost monitoring temperature probes. Temperature data were analyzed as separate readings at each height and depth, as well as averaged across all pile heights and depths to give an average pile temperature per sample date. There was an initial increase in pile temperature from ambient temperatures at project installation, followed by a 4 month long thermophilic phase of the decomposition process. During months 2 through 4, piles maintained average temperatures between 127–135 °F, then decreased during months 5 and 6 as microbial activity and ambient temperatures decreased, followed by a gradual increase throughout the remainder of the study, presumably in response to warmer ambient temperatures throughout the spring and summer months. Thermal imaging with a FLIR C2 handheld camera was also investigated as a potential technique to measure pile temperature.