Garrett Owen

Former Graduate Student

Degree: M.S., 2013

Thesis: Pine Wood Chips as an Alternative to Perlite in Greenhouse Substrates: Cultural Parameters to Consider

Since the transition to soilless growing media (substrates) in the 1960’s for container-grown horticultural plants, the basic components have been peat, coir, vermiculite, and perlite. Perlite is a lightweight, non-renewable, inorganic, silicaceous aggregate that allows aeration and gas exchange in substrates. The cost of perlite has increased significantly in recent years and is now the most expensive (by volume) component in horticultural substrates. The potential of using pine wood chips (PWC), produced from loblolly pine trees (Pinus taeda L.) as an aggregate has gained attention since 2010 and their use is significant (economically speaking) because of loblolly pines’ fast growth rate, regional availability, and abundance throughout the Southeastern US. The objectives of Garrett’s work were; 1) determine physical properties of peat-based greenhouse substrates containing various ratios of PWC compared to perlite, 2) determine the liming requirements (pH adjustment) for plant growth in peat substrates amended with PWC compared to perlite at various ratios, and 3) evaluate plant growth regulator (PGR) efficacy in substrates amended with PWC compared to perlite at various ratios. Garrett’s research demonstrated that PWC aggregates can replace perlite and be utilized in greenhouse substrates without greatly altering any of the cultural parameters of plant production that were tested. There were no differences between AS, CC, and TP of perlite or PWC substrates which suggests no change in irrigation practices is expected. Maximum plant growth (multiple species and multiple experimental replications) in PWC substrates was achieved at a lower lime rate of 3.56 kg·m-3 (6 lbs.yd-3) compared to perlite substrates. Pinewood chips do not appear to affect the efficacy of paclobutrazol drench activity on plant growth (multiple species and multiple experimental replications) which has been a concern of many growers. In addition to these objectives, Garrett also studied the effect of aging (harvest season and storage time) of PWC on plant growth performance and phytotoxicity and lastly he evaluated the disease susceptibility/suppressiveness potential of PWC aggregates compared to perlite in peat substrates.

W. Garrett Owen