S06 - Session P16 - Impact of Wood Addition to Sphagnum Peat on Substrate Water Capture through Surface and Subsurface Irrigation

Authors: Brian Schulker *, Brian Jackson

The effectiveness of a horticultural substrate to imbibe water through irrigation can be a determining factor in sustainable crop production. A reduction in substrate wettability can lead to lower water capture, excessive leachate, and poor plant growth. With the increased utilization of engineered wood components in growing media, much is unknown about how they change hydrological properties of peat-based substrates. To better understand the impact of wood components on water imbibition, hammermilled pine tree substrate (PTS) was combined in ratios of 20, 40, and 60% in Canadian sphagnum peatmoss and then tested under both surface and subsurface irrigation simulations to assess the impact of wood content on substrate water capture. Using both an ebb and flood subsurface irrigation unit and the NCSU wettability method, we evaluated the capillary capture intensity and gravitational capture intensity by using volumetric water content curves to identify the plateau where water uptake was maximized under 50% moisture content conditions. With surface irrigation, increasing wood content increased the amount of water imbibed by the substrate over 10 irrigation events, while also increasing the speed at which water was captured. Through subsurface irrigation, there was much less of an impact on imbibition. Water content within the substrate increased at the first irrigation event as wood ratio increased, showing that the wood content is aiding in reducing the hydrophobicity of peat. By the 10 th irrigation event, the differences were insignificant, with all substrate formulations capturing similar amounts of water. This shows that under greenhouse irrigation conditions, the increase in wood fiber amendment to Sphagnum peatmoss does not decrease the amount of water captured, but does increase the flow of water through the substrate, allowing more water to be captured over multiple events.