Effect of maize and peanut crops on Ivory Coast northern soil biological activities and their response to arbuscular mycorrhizal fungi inoculation

The overuse of chemical fertilizers in agriculture remains an environmental concern, especially in sub-Saharan areas of Africa where soil degradation lead to low crop yield. Crop inoculation with beneficial microorganisms appears a good alternative to reduce chemical substances and improve yield. In this regard, studies on soil biological activities and inoculation experiments on maize (Zea mays L.) and peanut (Arachis hypogaea L.) crops were conducted. The aim of this work was to evaluate the effect of these crops on soil microbial activities and to assess their response to inoculation with two fungi (Glomus aggregatum and Glomus etunicatum) alone or in combination. Rhizospheric and non rhizospheric soils were collected in peanut and maize fields at Takali in northern Côte d’Ivoire. Soil enzymes activities, total microbial biomass, AMF spore and rhizobia densities were determined in these soils. Then, mycorrhizal inoculation experiment of these plant species was conducted in a greenhouse located at Nangui Abrogoua University, Abidjan, Côte d’Ivoire. After three months, plant growth and yield, mycorrhizal and nodulation parameters were measured. Results showed that maize has significantly improved enzymes activities, spore density and total microbial biomass of soil. Effect of peanut was only significant on chitinase. Moreover, soil rhizobia density was reduced under this crop effect. Maize significantly improved these parameters more than peanut. Inoculation results showed a significant enhancement of the height and shoot dry weight of maize with single inoculation with G. aggregatum or G. etunicatum even if a low mycorrhization rate was observed. However, in peanut, the mixed inoculants (G. aggregatum + G. etunicatum) significantly increased the pod weight and nodulation parameters. Results showed the importance of plant cover in the improvement of soil biological quality including enzymes activities and microbial community and suggested that the effect of mycorrhizal inoculation is influenced by many factors as plant species, AMF and soil environment characteristics. Key words: A. hypogaea, Z. mays, soil enzyme activities, microbial biomass, soil microorganisms’ density, mycorrhizal inoculation.