This Is AuburnElectronic Theses and Dissertations

Particle Size Affects Physical and Chemical Properties of 100% Pine Bark Horticultural Substrate




Ware, Evan

Type of Degree

Master's Thesis




Pine bark is the most commonly used substrate component for container plant production in the southeastern United States, with some growers using 100% pine bark. Substrate physical and chemical properties directly affect the finished container-grown plant product. This study was developed to determine if there is a feasible way for growers to alter substrate physical and chemical properties to better suit the needs of the specific horticultural crop they are producing. Physical and chemical characteristics from locally sourced pine bark milled through two different screen sizes [0.50 inch (1.3 cm) and 0.75 inch (1.9 cm)] were compared the un-milled bark nuggets, as well as a standard substrate mix. Data showed that decreasing the particle size of a 100% pine bark substrate through milling does change physical and chemical properties. In this study, air space decreased as particle size decreased, water holding capacity increased as particle size decreased, total porosity increased as particle size decreased, and electrical conductivity and pH decreased as particle size decreased. This study suggests that producers can use milling to create a sustainable and cost-effective management of 100% pine bark substrates required for container-grown plant production. Index words: nursery, container-grown, pH