Reclamation strategies of semiarid mediterranean soil: improvement of the efficiency of arbuscular mycorrhizal fungi by inoculation of plant growth promoting microorganisms and organic amendments

Plant growth is limited in arid sites due to the adverse conditions coming from water stress. Moreover, soils from these areas are generally characterized by poor soil structure, low water-holding capacity, lack of organic matter and nutrient deficiency. In order to carry out a successful refforestation, it is necessary to improve soil quality and the ability of plants species to resist this harsh environment. Inoculation of plants with beneficial microorganisms such as Arbuscular Mycorrhizal Fungi (AMF) and others plant-growth promoting microorganisms (PGPM) may increase drought tolerance of plants growing in arid or semiarid areas. On the other hand, addition of organic amendments to the soil can reverse degradation of soil properties. Agro-waste residues such as dry olive cake (DOC) and sugar beet waste (SB) supplemented with rack phosphate (RP) can be used as organic amendments after fermentation by Aspergillus niger. it has been reported that the application of A. niger- treated DOC and/or SB to semi-arid soils increases aggregate stability, soil enzymatic activities, water soluble C and water soluble carbohydrates as well as nutrient availability, especially phosphorus (P). AMF inoculation, using autochthonous endophytes, has been shown to be more efficient with respect to increasing plant nutrition and growth as well as plant tolerance to drought than less adapted fungi. The combined treatments involving AMF and/or PGPM inoculation and addition of the amendments into the soil can be proposed as a successful revegetation strategy and a low-input biotechnology for plant performance in P-deficient soils under semiarid Mediterranean conditions. The analysis of co-operative microbial activities is addressed to improve the understanding of the significance of rhizosphere microbial populations.Peer reviewe