Dual inoculation of Pisum sativum with Rhizobium leguminosarum and Penicillium bilaji

Summary To investigate the effect of single versus dual inoculation of peas (Pisum sativum L.) with Rhizobium leguminosarum biovar viceae and Penicillium bilaji (a soil fungi capable of solubilizing soil P) on N₂ fixation an experiment was carried out under controlled conditions. A sandy loam soil was selected which contained low levels of available N and P. P fertilizer [Ca(H₂PO₄)₂] and P. bilaji significantly increased dry matter production. Peas inoculated with R. leguminosarum showed only a small increase in dry matter, but the additional application of P significantly increased the yield. The total N accumulation was highly dependent on the presence of R. leguminosarum. Using the ¹⁵N method for estimating N₂ fixation, the highest level of N₂-fixing activity was observed in peas inoculated with R. leguminosarum and fertilized with inorganic P. Dual inoculation of peas with P. bilaji and R. leguminosarum significantly decreased the amount of N₂ fixed. Total P uptake was solely dependent on the P fertilizer.