AbstractA field experiment was carried out to compare the effectiveness of inoculation with three arbuscular mycorrhizal (AM) fungi, namelyGlomus intraradicesSchenck & Smith,Glomus deserticola(Trappe, Bloss. & Menge) andGlomus mosseae(Nicol & Gerd.) Gerd. & Trappe, and the addition ofAspergillus niger‐treated dry olive cake (DOC) in the presence of rock phosphate, in increasing root nitrate reductase (NR) and acid phosphatase activities, mycorrhizal colonization, plant growth and nutrient uptake inDorycnium pentaphyllumL. seedlings afforested in a semiarid degraded soil. Three months after planting, both the addition of fermented DOC and the mycorrhizal inoculation treatments had increased root NR activity significantly, particularly the inoculation withG. deserticola(by 75 per cent with respect to non‐inoculated plants), but they had no effect on root acid phosphatase. Mycorrhizal inoculation treatments withG. deserticolaorG. mosseaeon their own were even more effective than the addition of fermented DOC alone in improving the growth and (NPK) foliar nutrients ofD. pentaphyllumplants. The combined treatment involving the application of microbially‐treated agrowastes and mycorrhizal inoculation with AM fungi, particularly withG. mosseae, can be proposed as a successful revegetation strategy forD. pentaphyllumin P‐deficient soils under semiarid Mediterranean conditions. Copyright © 2004 John Wiley & Sons, Ltd.