THE EFFECT OF AZOSPIRILLUM-BRASILENSE SP7 AND AZOTOBACTER-CHROOCOCCUM ON NITROGEN-BALANCE IN SOIL UNDER CROPPING WITH OATS (AVENA-SATIVA L)

Pot experiments with oats were carried out to study the effect of Azospirillum brasilense Sp 7 and Azotobacter chroococcum 94K on the yield of plants, the N content of soil and the N-14 balance. The plants were grown on gray forest soil under irrigation with deionized water and application of N-15-labelled fertilizer at a rate of 4 mg N 100 g-1 soil. Inoculation of plants with Azospirillum spp. and Azotobacter spp. failed to increase the plant yield. However, the increase in total N in the soil at the end of the experiment and the positive N-14 balance in the soil-plant system due to increase nitrogenase activity in the rhizosphere were statistically significant. The amount of N accumulated in the soil was comparable with the rate of N applied as fertilizer.