โ Scribed by Dr. S. H. Elwan; M. R. El-Naggar
No coin nor oath required. For personal study only.
An investigation was made on the role of microorganisms in affecting the growth behaviour of Azotobacter in the soil. Azotobacter chroococcum, Bacillus licheniformis, B. megaterium, Pseudomonus striata. Aspergillus niger, A . terreus, A . flavus, A . aydowi, A . nidulans, Fusarium sp., and Helminthosporium sp. were isolated from a sandy neutral soil. This soil was sterilized, one lot was kept as such, and another was supplemented with glucose and potassium phosphates. Azotobacter chroococcum was inoculated alone or in association with any of the above microorganisms. Counts of Azotobacter were made weekly during 14 weeks on nitrogen-free agar plates.
The results indicated the importance of the microbiological factor in affecting the growth behaviour of Azotobacter in t,he soil. A general pattern was observed showing a great decline for one week followed by a progressive increase more in non-supplemented than in supplemented soils. I n case of A. niger, however, a tendency of a decline was observed in the last 2 weeks.
The discussion showed that the variation of the microflora of different soils or the nonstationary microbial balance of a soil may contribute to the controversy of the results of the investigations of Azotobacter behaviour in the soil.
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