ARS | Publication request: Alternate Substrates for Bedding Plants

Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: August 1, 2006
Publication Date: December 1, 2006
Citation: Boyer, C.R., Fain, G.B., Gilliam, C.H., Gallagher, T.V., Torbert III, H.A., Sibley, J.L. 2006. Alternate Substrates for Bedding Plants. Southern Nursery Association Research Conference. 51:22-25.

Interpretive Summary: A new trend in harvesting pine trees is mobile in-field harvesting equipment, which processes trees into “clean chips” for pulp mills leaving behind a product composed of about 50% wood, 40% bark and 10% needles. This product, “clean chip residual” (CCR) is either sold for boiler fuel or, more commonly, left in the field and spread across the harvested area. This study evaluated this product as a potential new substrate component for the nursery industry. Results indicate that uniform crops of annual plants can be grown in clean chip residual with the addition of 0, 10 or 20% peat moss. Use of this product could provide an alternative to traditional pinebark and pinebark:peat moss based substrates.

Technical Abstract: The objective of this work was to evaluate fresh Clean Chip Residual (CCR) as a substrate component for production of container-grown annuals. Loblolly pine trees (Pinus taeda) (12 year old planted pine plantation) were thinned and processed for clean chips using a total tree harvester. The residual product (CCR) was further processed through a horizontal grinder with 4 inch screens. The sample used in this study was processed again to pass a ¾ or ½ inch hammer mill screen. CCR was blended with either 0, 10, or 20% peat and compared to pine bark. This study was conducted at the Paterson Greenhouse, Auburn University in Auburn, AL (April 12, 2006). Each substrate blend was pre-plant incorporated with a standard nutrient package. Two species, Ageratum houstonianum ‘Blue Hawaii’ and Salvia x superba ‘Vista Purple’, were greenhouse grown in trade gallon containers and irrigated by hand as needed. No differences among treatments were observed for media shrinkage at either 7 or 41 DAP. Substrate pH measurements were within acceptable ranges (5.5 to 6.5) for the duration of the study. Substrate EC measurements were generally high (3000-2560 'S/cm) among all treatments one DAP. At 15 DAP all substrate EC levels were higher than the recommended range (400-1000 'S/cm), but had decreased since one DAP. Substrate EC levels at 30 DAP indicated only one treatment in the recommended range (100% Pine Bark); all other treatments were above published acceptable levels. Chlorophyll content of Ageratum was greater than or equal to 100% Pine Bark. No differences in leaf chlorophyll content of Salvia were observed. Ageratum shoot dry weight indicated no differences among treatments. Salvia shoot dry was the greatest with all Pine bark treatments and all 4:1 Peat treatments, however all treatments were similar to 100% Pine Bark. Similarities among treatments in this study indicate that CCR is a potentially viable, sustainable, and economical substrate option for containerized nursery crop production. Species included in this test showed little or no differences compared to control treatments, indicating that growth in CCR can produce crops that are as marketable as those grown in pine bark alone. More studies need to be conducted in order to determine appropriate irrigation and fertilizer regimes as well as document the responses of many species to growth in CCR.