Sewage sludge and mycorrhizal effects on secar bluebunch wheatgrass in mine spoil

Establishing vegetation on mine spoil often requires amendments to supply nutrients and microorganisms to re-establish attributes associated with developed soil. Arbuscular-mycorrhizal fungi (AMF) and composted sewage sludge (CSS) were evaluated as possible mine-spoil amendments to create a topsoil substitute for revegetation of the Midnite Mine, Stevens County, Washington. Most original topsoil was buried and existing spoil is low in nutrients and organic matter and not capable of supporting desired vegetation. Secar bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) A. Love x Elymus lanceolatus ssp. lanceolatus (Scribn. & J.G. Sm.) Gould] was grown in nonsterile spoil amended with 0.0, 6.2, 12.4, 24.5, and 49.0 g dry CSS per liter of spoil-sand mix for 16 wk in a glasshouse experiment. Arbuscular-mycorrhizal fungi treatments were spores of Glomus mosseae [(Nicol. & Gerd.) Gerdemann & Trappe] collected from native bluebunch wheatgrass plants, non-native spores of Glomus intraradices (Schenck & Smith) and Entrophaspora sp. (Ames & Schneider), or no added spores. In addition, Secar was grown in nonsterile, stock-piled topsoil with both AMF treatments to compare to AMF present in the topsoil. Each CSS rate increase produced increased aboveground and belowground plant growth. Secar growth was enhanced by native AMF in CSS-amended spoil. Composted sewage sludge appeared to reduce AMF colonization; however, hyphae levels in plants with native AMF were unaffected. Plant growth was not affected by AMF treatments in stockpiled topsoil but AMF colonization was greater in plants with the topsoil alone. Benefits from CSS and selection of an effective AMF culture are evident.