Improvement of rhizosphere aggregate stability of afforested semiarid plant species subjected to mycorrhizal inoculation and compost addition

Soil aggregate stability is one of the most important properties controlling plant growth in semiarid Mediterranean environments. A field study was carried out to evaluate the effect of the rhizosphere of Olea europaea subsp. sylvestris and Rhamnus lycioides, the addition of a composted residue and mycorrhizal inoculation with Glomus intraradices on rhizosphere aggregate stability and on the viability of both plant species in a semiarid structureless soil. For both plant species, water-soluble carbon (WSC) content and enzyme activities (urease, acid phosphatase and β-glucosidase) measured in the rhizosphere aggregate were higher than in the non-rhizosphere soil. Rhizosphere aggregate stability of both plant species was on average 1.8-fold higher than that of non-rhizosphere aggregate. The addition of composted residue was the most effective treatment for increasing rhizosphere aggregate stability. The water-soluble carbon content was correlated positively with aggregate stability of the O. europaea rhizosphere. The mycorrhizal component was increasingly important for improving the growth of both seedlings following the addition of composted residue to soil under the severe climatological conditions of the area.