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 in the physical properties of longleaf pine bark over the course of twelve months of aging and how sand and white wood contaminants influence those properties. In this study the amount of white wood decreased from 6.3% at month 0 to 3.8% (by volume) at month 12 as a result of decomposition. Bark supplies/suppliers may have higher percent white wood present but that does not suggest the bark quality is bad. White wood is not detrimental to crop growth like once believed so this should have no negative effect on the quality of the bark substrate. The amount of sand that accumulated in the bark as a result of being piled on the ground and turned every month with a front-end loader was also calculated. At the beginning of the study (month 0) the sand content was 0.43% by volume and 2.8% by weight of the pine bark. At month 6 the sand content was 0.02% by volume and 14.05% by weight. At month 12 the sand content was 3.19% by volume and 20.15% by weight. The high sand content found in this study was a result of the sandy soil of the testing location. All bark supplies/suppliers may not have the same sand accumulations. This sand percent (and weight) can be significant in shipping weights and should be monitored/considered.