| Abstract |
This experiment was designed to elucidate the environmental factors in rhizospher of bamboo forest that affect the distribution and the population size of Azotobacter, and also to estimate the annual productivities of nitrogen fixed by Azotobacter species. The results of this experiment can be summarized as follows ; The rhizosphere of bamboo forest contained high free sugars as of 3-8 times more than non-rhizosphere (Bacon, 1968), and the contents of organic matter and amino acids of that are relatively higher than this. Because of high content of potassium, average of soil pH is near at 7.0. As above-mentioned environmental factors, the population sizes of Actinomycetes, general fungi, general bacteria and Azotobacters are larger than those of non-rhizosphere and the other rhizosphere. The dominant group in the rhizosphere is Actinomyvetes and the followings are general fungi and general bacteria by turns. Azotobacter is dependent upon the antagonistic Actinomycetes. The main carbon source for Azotobacter in nitrogn flxation at the rhizosphere was glucose and minors were fructose, maltose and sucrose by turns. Annual gains of nitrogen by Azotobacters in soil of bamboo forest within 10cm from surface are estimated as of 88.94 kg/ha at site A, 60.4kg/ha at site B and 67.38kg/ha at site C, respectively. |
