Dual inoculation of Pisum sativum with Rhizobium leguminosarum and Penicillium bilaji

Non-Peer ReviewedTo investigate the effect of single versus dual inoculation of Trapper-pea with Rhizobium leguminosarum and Penicillium bilaji, a P-solubilizing fungi, an experiment under controlled conditions was carried out using a sandy soil containing low levels of available N and P. The following treatments were installed: control, P application at a rate of 100 kg P/ha, pea inoculated with P. bilaji (PB50) applied at recommended rate as PB50™ supplied by Philom Bios, pea inoculated with R. leguminosarum (R) and all possible combinations of the four treatments. To determine N2 fixation by 15N-natural abundance, flax was included as the reference crop. Treatments were replicated four times and placed in a randomized complete block design. Throughout the experiment, soil was kept at 75 % of field capacity and additional light was provided. After 8 weeks of growth, two plants/pot were harvested and total shoot weight, total N, total P, percent N derived from N2 and the amount of N2 fixed was determined. P fertilization increased yield significantly from 3.0 to 4.2 g/pot. PB50 alone increased shoot yield to 3.6 g/pot. Whereas pea inoculated with R showed only a small yield increase, the additional application of P increased yield to 4.1 g/pot. Application of P and both the inoculants reduced yield to 3.7 g/pot. Total N accumulation was highly dependent on the presence of R. Whereas the control, which was sparsely nodulated, showed a total N yield of 62.3 mg N/pot, inoculation with R and P fertilization increased total N to 100 mg N/pot. Double inoculation with Rand PB50 along with P fertilization reduced the total N yield to 95 mg N/pot. Pea inoculated with PB50 and R showed a total N yield of 78.5 mg N/pot. The highest N2-fixing activity (39 % Ndfa or 39.6 mg of N) was observed in pea inoculated with R and which had received inorganic P. Total P uptake was solely dependent on P fertilization. Results indicate that PB50 had no beneficial influence on P uptake and N2-fixing activity