Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2009
Publication Date: 12/1/2009
Citation: Altland, J.E., Krause, C.R. 2009. Use of Switchgrass as a Nursery Container Substrate. HortScience. 44(7)1861-1865.
Interpretive Summary: Pine bark is the primary component used in outdoor nursery production. A decrease in forest products output, coupled with increased use of bark as a fuel at paper and lumber mills, has caused a decline in pine bark inventories available for horticultural use. Increasing demand for wood-based ethanol over the next 20 years will cause even greater competition for pine bark and other woody biomasses. Due to decreasing availability and increasing costs, the objective of this research was to determine if a biomass crop, switchgrass (Panicum virgatum), could be harvested and used as a nursery substrate. Switchgrass substrates ground to a sufficiently small particle size, and/or amended with peat moss, had suitable physical properties for container crops. Substrate pH in switchgrass substrates were relatively high, but easily adjusted with peat moss amendment. Foliar Ca and Fe levels were marginally low in switchgrass substrates, but not so low that they adversely affected plant growth. These nutrient deficiencies would be relatively easy to remedy with typical nursery fertilizers. Roses grew well in switchgrass substrates with adequate root and shoot growth.
Technical Abstract: Pine (Pinus taeda L.) bark is the primary component of Nursery container crops in the eastern U.S. Shortages in pine bark prompted investigation of alternative substrates. The objective of this research was to determine if ground switchgrass (Panicum virgatum L.) could be used for short production-cycle woody crops. Two experiments were conducted using ‘Paprika’ roses (Rosa L. ‘ChewMayTime’) potted in 15 cm tall and wide containers. In Expt. 1, substrates were composed of coarse switchgrass (processed in a hammermill with 1.25 and 2.5 cm screens) amended with 0%, 30%, or 50% peat moss and fertilized with 100, 250, or 400 mg.L-1 N from ammonium nitrate. In Expt. 2, substrates were composed of coarse (similar to above) or fine switchgrass (processed through a single 0.48 cm screen), amended with 0% or 30% peat moss, and fertilized with the same N rates in Expt. 1. Summarizing across both experiments, coarse switchgrass alone had high air space and low container capacity. Fine switchgrass had physical properties more consistent with what is considered normal for nursery container substrates. Switchgrass pH was generally high and poorly buffered against change. Fine switchgrass had higher pH than coarse switchgrass. Rose tissue analysis revealed low to moderate levels of calcium and iron, but all other nutrients were within normal ranges. Despite varying physical properties and pH levels, all roses at the conclusion of the experiment were of high quality. Switchgrass processed to an appropriate particle size, and amended with typical nursery materials should provide a suitable substrate for short production-cycle woody crops.