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Longevity of Azotobacter in Soils Treated with Lime and Superphosphate 1
Author(s) -
Vandecaveye S. C.,
Anderson S.
Publication year - 1934
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1934.00021962002600050002x
Subject(s) - azotobacter , citation , lime , soil water , longevity , mathematics , library science , computer science , biology , environmental science , soil science , gerontology , medicine , paleontology , genetics , bacteria
The Azotobacter group, though widely distributed over vast areas of the earth’s surface, has been found absent in many soils. In a memoir in which previous work on the non-symbiotic nitrogen-fixing bacteria is reviewed, Winogradsky (z~) ’~ estimated that approximately 50% of the soils examined are devoid of Azotobacter. The absence of the~e organisms in the soil has been attributed variously to insufficient amounts of lime, to lack of basicity, to a deficiency of phosphorus, or to a combination of these factors. A careful study of the available literature on the occurrence of Azotobacter in soil made by Gainey (4) showed a close correlation between the absolute reaction of the soil solution and the presence or absence of these bacteria. He came to the conclusion, largely from the results of liquid culture media, that very few acid soils with a pH value below 6.0 contain Azotobacter, whereas soils with reactions of a higher pH value contain these bacteria in most instances. Liquid culture media, however, do not supply favorable conditions for the growth of aerobic bacteria so that results thus obtained are probably not representative of the natural conditions existing in the soil. Winogradsky (~ z) pointed out that Azotobacter colonies, naturally fixed and growing on soil particles, are forced to start growth under submerged condition in a more or less thick layer of liquid when introduced into liquid culture media, whereas they are in direct contact with the air, which is natural for them, when introduced into the soil. The characteristic film on liquid media is produced most likely by motile forms rising to the surface where they face strong competition with other organisms. Furthermore, these media become charged with carbonic acid and are almost invariably subjected to butyric acid fermentation so that it is conceivable that the brown film, the sure sign of Azotobacter growth in liquid cultures, can be formed only when the soil carried down in the liquid contains a