Seed inoculation with Azotobacter chroococcum in sand cultures and its effect on nitrogen balance.

The effect of bacterization of barley grains with a selected strain of Azotobacter chroococcum was studied. In nitrogen-deficient sand, seed inoculation increased plant length, dry weight, nitrogen content in addition to a significant increase in soil nitrogen. The density of the organism on grains had a slight positive effect. Irrigation with KNO3-containing nutrient solution suppressed nitrogen fixation, but inoculation still had a pronounced stimulating effect on plants. In presence of mixed soil microflora the beneficial effect of bacterization was less than in monobacterial cultures. Azotobacters naturally present in soil also colonized in heavy densities on the rhizoplane, but their effect on plant growth and soil nitrogen were less if compared with that resulting from bacterization.