Response of Cowpea to Symbiotic Microorganisms Inoculation (Arbuscular Mycorrhizal Fungi and Rhizobium) in Cultivated Soils in Senegal

Abstract

The response of cowpea [Vigna unguiculata (Walp. (L.)] to inoculation with symbiotic microorganisms (arbuscular mycorrhizal fungus and rhizobium) was investigated on cultivated vertisoils (known locally as Dek) and arenosoils (known locally as Dior) in three geographic sites in Senegal. On the basis of soil physico-chemical characteristics, of most probable number (MPN) of indigenous rhizobia and of yields, a hierarchical analysis showed that the sites were grouped in three clusters. Some soils initially considered as Dek were grouped with Dior, so that all of Dior soils were grouped in the same cluster. No significant increasing in shoot biomass or yield was observed when cowpea was inoculated with fungi alone, whatever soil type. However, a significant or noticeable improvement in cowpea seeds production was obtained by rhizobium inoculation. It appeared that cowpea response to inoculation depended on geographical site and were often observed in sandy arenosoils (Dior type) or in loamy sand vertisoils (Dek type) with at least 15mgkg^-1 of available phosphorus level.