ARBUSCULAR MYCORRHIZA (AM) IN ASSOCIATION WITH RHIZOBIUM SP IMPROVES NODULATION, N-2 FIXATION, AND N UTILIZATION OF PIGEON PEA (CAJANUS-CAJAN), AS ASSESSED WITH A N-15 TECHNIQUE, IN POTS

Nodulation and grain yield of pigeon pea (Cajanus cajan) were signific antly increased due to Rhizobium sp. and Glomus fasciculatum (AM) inoc ulation when the plants were grown in pots of unsterilized soil, espec ially when fertilized with 50 kg P2O5 ha(-1). Soil inoculation with AM fungi alone increased the nodulation of pigeon pea. Using the N-15 di lution technique [((NH4)-N-15)(2) SO4] at the rate of 20 kg N ha(-1) i t was possible to determine the increase in total N yield of the crop, utilization of fertilizer N, and biologically fixed N-2 with AM inocu lation, which was about equivalent to Rhizobium sp. inoculation. More N-2 was fixed with a combination of Rhizobium sp, and VAM. The effects were more pronounced when P (50 kg P2O5 ha(-1)) was applied in combin ation with N (20 kg N ha(-1)) in the form of super phosphate and ammon ium sulphate, respectively. However, biologically fixed N-2 was estima ted to be higher in straw than in grain which indicates a difference i n translocation and utilization of fixed N-2.