Abstract

The aim of this study was to determine not only the activity of the nitrogenase enzyme, the fixed nitrogen in the day-round of Suwan 5 maize when inoculation with Azotobacter chroococcum and Azospirillum lipoferum but also the correlation between the nitrogenase activity and total fixed nitrogen. The statistical arrangement was 3 × 4 factorial in completely randomized design with 4 replications. The first factor was inoculation (Azotobacter chroococcum, Azospirillum lipoferum and non-inoculation (control)). The second factor was the observation time of nitrogenase activity (6:00, 12:00, 18:00, 24:00 hr.). The data were collected at 4 and 6 weeks. The results showed that the different time in a day-round did not affect the nitrogenase activity. Inoculation of azotobacter gave the highest total soil nitrogen at 4 and 6 week. (729.77 and 750.47 mg/10 kg-soil) while, the highest total plant nitrogen was found as inoculated with azospirillum (159.11 and 840.35 mg/plant of 4 and 6weeks). However, the total fixed nitrogen of azotobacter and azospirillum treatments were in the same level. Azotobacter treatment gave higher nitrogenase activity in soil than that of azospirillum treatment, while that in plant it was lower. The total nitrogenase activities of both inoculums were not different during the time of this study. The bulk (over all) correlation of total fixed nitrogen and total nitrogenase activity at week 4 and 6 were linear equations as y = 0.0224x + 18.045, R²= 0.8687 and y = 0.0117x + 14.57, R²= 0.7604 respectively.

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