Symbiotic Efficiency of Acacia cyanophylla Lindl and Acacia pycnantha Benth in Four Soil Types

The present study aims to evaluate the interaction between soil rhizobia and legume plant, by comparing two Acacia species (Acacia cyanophylla Lindl and Acacia pycnantha Benth) grown in four different Moroccan soils, by measuring plant dry matter yield, and nodule numbers and weights. Plants were harvested 9 month after seeding. We observed that Acacia cyanophylla Lindl nodulated in all the four soils. Plant nodule numbers and yield were significantly enhanced by native soil rhizobia. Acacia pycnantha Benth nodulated only in one type of soil. After nodulation and isolation of nodules, A. cyanophylla was nodulated by rhizobia strains. In this experiment, the statistical results revealed a significant correlation between the number of nodules per plant and plant height (r = .87, P <.05), these results show that adequate nodulation improves the establishment and the plant growth. We recommend using rhizobial biodiversity in arid and desert areas if the plants do not have the ability to establish a symbiosis with native rhizobia. Inoculation of Acacia seeds during the establishment in nurseries improves growth and N2 fixation. The symbiotic nitrogen-fixing bacteria have been selected and conserved in Moroccan collection. These rhizobia may be used to inoculate wild, as well as, crop legumes, cultivated in reclaimed desert lands.