The 2012 ASHS Annual Conference

Much work has been done to determine the moisture characteristics of various components of horticultural substrates. However, wood based components have not been fully explored. Moisture retention curves of two wood materials were compared to some traditional substrate components peat, coir, and perlite. Freshly harvested loblolly pine (Pinus taeda L.) logs were hammer-milled through a 6 mm (1/4 in.) screen after being initially processed with either a wood chipper or a wood shredder. The chipped process produced a “blockular” aggregate type product (WC), while the shredding process produced a more fibrous material (SH). The WC and SH had total porosities of 78% and 84%, respectively, which was lower than that of the peat and coir and higher than the perlite. Air filled porosity between 0 and free drainage (3.8 cm) was two to three times greater in WC and SH compared to peat, coir, and perlite. WC and SH tended to have very similar curves as a whole, yet SH tended to hold slightly more water at all points than WC. The WC and SH tended to release a larger majority of their water at very low pressures than that of the peat, coir, and perlite. Under the highest pressure settings, 100, 200, and 300 cm, the WC and SH tended to hold water similarly to peat and perlite, with coir releasing more than the others. This research has identified the water retention properties of SH and WC which will be helpful in finding the best scenarios for their use as components for greenhouse substrates.