RESPONSE OF WHEAT TO DUAL INOCULATION WITH VA-MYCORRHIZA AND AZOSPIRILLUM, FERTILIZED WITH NPK AND IRRIGATED WITH SEWAGE EFFLUENT

A study was performed to investigate the dual effect of inoculation with Azospirillum and VA-mycorrhiza on wheat growth and nutrition. The effects of irrigation with sewage water and NPK fertilization were determined. Potted wheat plants in a greenhouse were used. The highest increase in dry matter production and N and P content was recorded for NPK and VA-mycorrhiza + Azospirillum treatment. Inoculation with either VA-mycorrhiza or Azospirillum had similar effects on wheat growth, while inoculation with both organisms result in higher growth increase than either of them alone. The percentage increase of shoot dry matter over the control group was 56.7, 16.2, 21.6, and 37.8% for NPK, VA-mycorrhiza, Azospirillum, and VA-mycorrhiza + Azospirillum treatment, respectively. A similar increase was found with roots and spikes. Also, the inoculation of VA-mycorrhiza with Azospirillum caused an increase in acetylene reduction activity; hence, it reached an average of 60 and 90 times that of the inoculated control in the cases of inoculation with Azospirillum and VA-mycorrhiza + Azospirillum, respectively. Irrigation increased dry matter production and N and P content of plants. The increases were higher when undiluted sewage water was used for irrigating plants, as compared to 1:1 tap and sewage water dilution or tap water alone. Dry matter production and N content of plants were correlated with nitrogenase activity in both rhizosphere and root-free soil. N and P content and dry matter production were significantly correlated with VA-mycorrhizal infection. VA-mycorrhiza was found to stimulate Azospirillum, indicating that both contributed to the growth and nutrition of wheat.