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We examined the long‐term success of prairie planting on a former strip mine in northeastern Illinois. The site was reclaimed and planted with prairie species in the 1970s. Total biomass increased over time, largely as a result of an increase in biomass of non‐prairie species. Biomass of prairie species remained unchanged because of an increase in Panicum virgatum (switchgrass) offsetting decreases in Sorghastrum nutans (Indian grass). Total biomass was less than values published for other restored prairies (78 ± 4 g/m2to 298 ± 72 g/m2 for our site, as opposed to 302‐489 g/m2 for the Trelease Prairie). Mycorrhizal inoculum potential (MIP) was variable across the site. There were also relatively few species of mycorrhizal fungi present as spores. Gigaspora sp., Scutellospora sp., Glomus sp., Glomus geosporum, and Glomus cf. fasciculatum were identified from spores. On a transect dominated by warm‐season (C4) prairie grasses, MIP of rhizosphere soil collected under these species was lower than the MIP of rhizosphere soil collected under exotic cool‐season (C3) grasses on a transect dominated by C3 species. On a transect with mixed warm‐and cool‐season vegetation, however, MIP did not differ under the two vegetation types. These results suggest that within‐site patchiness rather than cover type is influencing MIP. Values of MIP were lower than those reported for native Illinois prairie.

The growth response of prairie switchgrass (Panicum virgatum L.) was compared in strip mine spoil amended with various levels of anaerobically digested waste‐activated sewage sludge (0, 56, 111, 222, or 333 dry Mg ha−1) and commercial fertilizer, pure sludge, and glasshouse soil. Plants were grown in a growth chamber and substrates were maintained at field capacity during the study. Soluble salt concentrations of the substrates increased linearly as a function of sludge amendment and were within the range known to inhibit the growth of many plant species at the high levels of sludge application. There was, however, a linear response of biomass production to increasing levels of sludge amendment. Maintaining substrates at field capacity apparently prevented the high concentration of soluble salts from inhibiting plant growth. The increased biomass yield associated with sludge application was likely due to the increased availability of inorganic nutrients associated with sludge amendment.

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