Recently, the limited availability of Sphagnum peat moss due to poor weather conditions impacting harvests, and additional scrutiny from media and public outlooks has brought up serious questions about the long-term security of peat use in the horticulture industry. The search for alternative amendments began decades ago, with several products being evaluated over the years. Many have been found suitable for niche production settings, with few seeming to fit the industry somewhat ubiquitously. Of these, wood fiber is seemingly the most promising as it is a renewable resource that is available globally. Wood fiber amendments have been trialed extensively with industry emerging and scaling internationally. Wood can be processed to support many different applications in horticulture, giving it more robust qualities than other top components. There are some disadvantages to wood usage, namely, nitrogen immobilization. Wood contains large amounts of easily degradable carbon. Therefore, microorganisms will consume this carbon for energy by utilizing plant available nitrogen causing plant nutrient deficiencies. Microbial community activity is heavily influenced by moisture. Considering this, a study was developed to observe how the microbial activity of different hammermilled wood tree species may be influenced by moisture content in a greenhouse crop production cycle. Five tree species (Abies concolor, Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Pseudotsuga menziesii) were harvested in California and hammermilled. The wood particles were blended with a commercial peat-based substrate at 30% (by vol.). Supertunia ‘Honey’ plugs were planted in each of the substrate blends and grown on a greenhouse bench for 75 days. The crops were held at 25% and 35% volumetric water content using cantilever-style lysimeters and fertigated with water-soluble fertilizer, weekly. Crop growth and performance was assessed throughout production. Substrate CO2 was assessed pre- and post- production to assess microbial activity. The results will help assess the potential of utilizing differing tree species for wood fiber, and understand any adjustments that will be necessary to production practices.
