SEWAGE-SLUDGE AND MYCORRHIZAL EFFECTS ON SECAR BLUEBUNCH WHEATGRASS IN MINE SPOIL

Establishing vegetation on mine spoil often requires amendments to sup ply 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, S tevens County, Washington. Most original topsoil was buried and existi ng spoil is low in nutrients and organic matter and not capable of sup porting desired vegetation. Secar bluebunch wheatgrass [Pseudoroegneri a spicata (Pursh) A. Love x Elymus lanceolatus ssp. lanceolatus (Scrib n. & 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 treatment s were spores of Glomus mosseae [(Nicol. & Gerd.) Gerdemann & Trappe] collected from native bluebunch wheatgrass plants, non-native spores o f Glomus intraradices (Schenck & Smith) and Entrophaspora sp. (Ames & Schneider), or no added spores. In addition, Secar was grown in nonste rile, stock-piled topsoil with both AMF treatments to compare to AMF p resent in the topsoil. Each CSS rate increase produced increased above ground and belowground plant growth. Secar growth was enhanced by nati ve AMF in CSS-amended spoil. Composted sewage sludge appeared to reduc e AMF colonization; however, hyphae levels in plants with native AMF w ere unaffected. Plant growth was not affected by AMF treatments in sto ckpiled topsoil but AMF colonization was greater in plants with the to psoil alone. Benefits from CSS and selection of an effective AMF cultu re are evident.