Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/1998
Publication Date: N/A
Interpretive Summary: Mine spoil is often characterized as having low fertility, organic matter, water holding capacity, and soil biological activity, yet it is used as a substitute for topsoil in surface-mine revegetation when topsoil is lacking. Spoil created from open-pit surface mining is a mix of soil and rock produced from excavation of ore veins and is generally devoid of physical and biological attributes associated with developed topsoil. Since revegetation objectives may not be met if a suitable soil environment is not provided, amendments such as composted sewage sludge (CSS) and arbuscular-mycorrhizal fungi (AMF) are added to mine spoil to help create a functional soil. The addition of CSS to mine spoil greatly enhanced the growth of Secar bluebunch wheatgrass during the 16-week glasshouse experiment. Establishment of Secar in low-nutrient mine spoil likely would not occur without amendments to improve the nutrient and organic matter status of the spoil. The addition of CSS may bridge the gap between an immature soil environment and late-seral vegetation. Native- AMF inoculum provided superior quantity and quality of Secar growth in CSS-amended mine spoil. The improved vigor of Secar should translate into greater cover of the disturbed ground and improved competitive ability. These results also suggest that selection of AMF, as well as other soil biota, should be considered when selecting plant species and amendments for revegetation of highly disturbed land.
Technical Abstract: 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 Co., WA. 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 non-sterile 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 weeks in a glasshouse experiment. AMF 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 non-sterile, stockpiled 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. CSS 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.