Use of Processed Biofuel Crops for Nursery Substrates

Abstract

Loblolly pine (Pinus taeda) bark availability has decreased, causing shortages in inventory and increased prices for pine bark substrates. One potential alternative to pine bark is the use of biofuel or biomass crops that can be grown locally, harvested, and processed into a suitable substrate. The objective of this research was to assess the suitability of several biofuel crops as alternatives to pine bark in nursery substrates using annual vinca (Catharanthus roseus) as a model crop. Across two experiments, switchgrass (Panicum virgatum), willow (Salix spp.), corn (Zea mays) stover, and giant miscanthus (Miscanthus ×giganteus) were processed through a hammermill equipped with a 0.95 cm (0.375 in) screen. Pine bark was used as a control. Substrate materials were used either alone, amended with 20% (v/v) sphagnum peat moss, or amended with 20% (v/v) sphagnum peat moss and 10% (v/v) municipal solid waste compost. Biofuel-based substrates tended to have greater air space and less container capacity than pine bark substrate. Amending with peat moss, or peat moss and municipal solid waste compost reduced air space and increased container capacity of all substrates. Substrate pH of biofuel-based substrates was higher than pine bark substrates, and was neutral to slightly alkaline. Amending with peat moss reduced pH of biofuel substrates to levels considered more ideal for annual vinca growth. Foliar calcium, magnesium, and iron levels were low across all treatments, although visual foliar deficiency symptoms were not apparent. Shoot growth was greatest in switchgrass and pine bark substrates. Plant growth differed among biofuel and pine bark substrates; however, all plants were considered marketable at the conclusion of the experiment. Modification of chemical and physical properties for each substrate type will be necessary.