Medium-term effects of mycorrhizal inoculation and composted municipal waste addition on the establishment of two Mediterranean shrub species under semiarid field conditions

The development of appropriate revegetation techniques is essential to reduce and to remediate the processes of erosion and desertification in semiarid Mediterranean areas. A factorial field experiment was carried out in a degraded semiarid Mediterranean area to assess the effectiveness of composted municipal waste addition to soil, mycorrhizal inoculation with Glomus intraradices and the combination of both treatments on the viability, growth and nutrition of Olea europaea L. subsp. sylvestris and Rhamnus lycioides L., over a 2-year growth period. Six months after planting, only mycorrhizal inoculation of O. europaea subsp. sylvestris and R. lycioides seedlings grown in the soil, with or without addition of composted municipal waste, statistically and significantly increased the shoot biomass and contents of foliar nutrients (N, P and K). During the last 6 months of the growth period, both shrub species displayed sharp increases in the shoot biomass. Two years after planting, the highest increases in the shoot biomass of O. europaea plants were recorded in the combined treatment of composted municipal waste addition and mycorrhizal inoculation (about 12-fold greater than control plants). The shoot biomass of R. lycioides was increased by composted municipal waste addition (about 226%) to a greater extent than by mycorrhizal inoculation (about 87%), at the end of the 2-year growth period. For both shrub species, there was a positive statistically significant correlation between shoot biomass, foliar contents of N, P and K and soil aggregate stability. Composted municipal waste addition, mycorrhizal inoculation and, in some cases, the combination of both treatments can be employed as effective tools in programmes using shrub species for revegetation of semiarid areas.