Effect of ecosystem changes on the population of nitrogen fixing bacteria group Azospirillum sp.
2001
Prasan Lonut(Maejo University, Chiang Mai (Thailand). Faculty of Agricultural Production. Department of Agronomy) | Settha Siriphin(Maejo University, Chiang Mai (Thailand). Faculty of Agricultural Production. Department of Agronomy)
Results indicated that the highest population of plant-associated nitrogen fixing bacteria group Azospirillum sp. in the range of 1.73-2.48 cell per gram dried soil (log number of cell/g dry soil) was found in soils with organic matter content between 1.5 to 10.9 percent and soil pH in the ranges of 4.4 to 6.6. Soils from agricultural fields especially in the continuous paddy rice tended to have more bacterial population than soils from undisturbed natural ecosystems. This was because the mountainous ecosystems have conditions of lower pH, higher soil organic matter and moisture contents that were not favorable for growth and development of the bacteria. The major morphological characteristics of the bacteria. The major morphological characteristics of the bacterial colony consisted of circular shape, medium size, white pigments, flat surface, less stickiness, and short rod cell with negative gram stains. The nitrogen fixation efficiency of the bacteria isolates was in the in the ranges of 1.20 to 1,291 nmolC2H4/mg protein/day. This indicated that there were diversities in bacteria group Azospirillum sp. under different natural conditions. Further selection of nitrogen fixing bacteria should lead to generation of know ledges that can be applied commercially and be useful in future natural resources management.
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