The field inoculation of Acacia saligna with efficient rhizobia strains for sand quarry restoration in Algeria

Abstract

Sand quarries constituting very specific environments where native plants and surface soil are destroyed. The resulting substrates are practically sterile from an organic and biological point of view due to the absence of humus, microfauna and flora. planting legumes like Acacia saligna inoculated with his microbial partner rhizobia is strategic key to enhance the substrate fertility and lead to an ecological restoration of sandpits. Here we have selected the most efficient couple A. saligna-rhizobia with the goal to rehabilitate Sidi Lakhdar sandpit in the end of exploitation and to follow the filed persistence of introduced rhizobia into A. saligna nodules. The in vitro efficiency test permitted the selection of three inocula which performed differently once transferred onto natural soil and in the field. The ASB13 (Ensifer sp.) were found to be better inoculum for sandpit rehabilitation and A. saligna-rhizobia couple introduction for above and underground degraded sites. The introduced rhizobia didn’t persist in nodules of A. saligna in different treated blocks which were revealed by the PCR-RFLP profiles after the digestion by restriction enzyme HaeIII. These results support the literature data on failure/success of inoculants pertain to the persistence of rhizobia (inoculants) in soil, inoculant success is affected not only by environmental conditions such as temperature, pH, salinity but also by competitivity of indigenous rhizobia. We conclude that the rhizobia-based inocula selection for field application necessitates testing selected strains under the environmental conditions prevailing in the site intended to be rehabilitated.