Utilization of Re-processed Anaerobically Digested Fiber from Dairy Manure as a Container Media Substrate

Authors: MACCONNELL, C - Washington State University; Collins, Harold

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2009
Publication Date: 6/24/2009
Citation: Macconnell, C.B., Collins, H.P. 2009. Utilization of Re-processed Anaerobically Digested Fiber from Dairy Manure as a Container Media Substrate. Acta Horticulturae. 819: 279-286.

Interpretive Summary: The solid fraction (fiber) from the effluent of the anaerobic digestion of dairy manure by plug flow technology yields material that has consistent physical properties (total porosity, air filled porosity at saturation, and water holding capacity) to perform satisfactorily as a plant growth media substrate. Since September 2002, 28 greenhouse trials have been conducted using anaerobic digester fiber as a 1:1 replacement for peat moss in container media. Plants grown in unamended fiber have robust root systems, but chlorotic shoots which initial trials indicated is due to unavailability of Fe & Mn. Various methods were used to increase availability of Fe & Mn by acidification and/or supplementation. A simple post digestion acidification treatment process has been developed to produce plants with shoot fresh and dry weight, size, and “greenness” equal to or better than peat moss based media, but which have a stunted root system. In subsequent trials, root digital images were analyzed using software to find differences in root development between treatments. The addition of a second post digestion amendment has produced plants that have large root systems and large, green shoots equal to or better than peat moss based media for a number of common greenhouse crops.

Technical Abstract: The solid fraction (fiber) from the effluent of the anaerobic digestion of dairy manure by plug flow technology yields material that has consistent physical properties (total porosity, air filled porosity at saturation, and water holding capacity) to perform satisfactorily as a plant growth media substrate. Since September 2002, 28 greenhouse trials have been conducted using anaerobic digester fiber as a 1:1 replacement for peat moss in container media. Plants grown in unamended fiber have robust root systems, but chlorotic shoots which initial trials indicated is due to unavailability of Fe & Mn. Various methods were used to increase availability of Fe & Mn by acidification and/or supplementation. A simple post digestion acidification treatment process has been developed to produce plants with shoot fresh and dry weight, size, and “greenness” equal to or better than peat moss based media, but which have a stunted root system. In subsequent trials, root digital images were analyzed using software to find differences in root development between treatments. The addition of a second post digestion amendment has produced plants that have large root systems and large, green shoots equal to or better than peat moss based media for a number of common greenhouse crops.