1. ABUNDANCE AND DIVERSITY OF AZOTOBACTER AND PO4 -SOLUBILIZING
MICROORGANISMS IN DIFFERENT LAND USE TYPES IN WESTERN GHATS OF
KARNATAKA
M. C. Vinutha, A. N. Balakrishna, K. T. Prasanna, N. G. Kumar and Balakrishna Gowda
1. Department of Agricultural Microbiology/ 2. Department of Entomology/ 3. Department of Forestry and Environmental Sciences
University of Agricultural Sciences, GKVK Campus,
Bangalore-560065, India
INTRODUCTION Population of Azotobacter in different land use types during pre and post-monsoon seasons
Population (cfu X 103g-1 soil) CD at 0.05
The heterotrophic free-living nitrogen fixers like Land use types Pre-monsoon Post-monsoon
Azotobacter, Beijerinckia, Derxia etc. are important due season season
to their wide occurrence in soils and rhizosphere of Natural forests 53 (7.14) a 21 (4.23) a 0.87
different crops. In India, there has been some work on Grasslands 13 (3.05) c 3 (1.37) b 0.93
the occurrence of azotobacters in different soils and Acacia plantations 14 (3.27) b 10 (2.35) a 1.36
different crops rhizospheres (Raghuramulu, 2001). Cardamom plantations 35 (5.75) a 12 (2.81) a 0.77
Coffee plantations 29 (5.30) a 18 (2.07) a 0.72
The insoluble inorganic and organic forms of
Paddy fields 14 (3.26) b 0.0 (0.70) c 0.91
phosphorus which constitutes a large portion of P in soil F-test * * -
is non available to plants. Many fungi and bacteria are Note: The values in the brackets are the transformed values using the square root transformation √
potential solubilizers of bound phosphates in soil. There x + 0.5
Note: NF: Natural forests, GL: Grasslands, ACP: Acacia plantations, CAP: Cardamom plantations,
have been several reports on phosphorus solubilizing COP: Coffee plantations, PF: Paddy field, ND: Not detected.
microorganisms in different soils (Thomas and
Shantaram, 1986). Abundance (cfuX104) of Azotobacter in different land use types in pre and post-monsoon seasons
Pre-monsoon season Post-monsoon season
MATERIAL AND METHODS Organism Land use types
NF GL ACP CAP COP PF NF GL
Land use types
ACP CAP COP PF
Study site: Koothi village, Somvarpet Taluk, Kodagu A.vinelandii 394 91 86 329 272 103 105 11 62 131 125 ND
District, Karnataka, India [Nilgiri Biosphere Reserve A.chroococcum 82 12 ND 129 190 12 86 11 ND 26 65 ND
Note: NF: Natural forests, GL: Grasslands, ACP: Acacia plantations, CAP: Cardamom plantations,
(Western ghats)] COP: Coffee plantations, PF: Paddy field, ND: Not detected
Annual rainfall: 2500 to 3500mm
Seasons: Pre- and Post-monsoon seasons (February and Population of PO4- solubilizing fungi in different land use types during pre and post-monsoon
November) seasons
Ecosystems sampled and sampling points: Natural Land use types
Population (cfuX103 g-1 soil) CD at 0.05
Pre-monsoon season Post-monsoon season
forest (9), Grassland (8), Acacia plantation (6), Coffee
Natural forests 20.01 (4.18)a 13.20 (2.08)a 0.560
(16), Cardamom (13) and Paddy (8). Grasslands 2.10 (1.18)c 1.50 (1.20)a 0.596
Abundance of Azotobacter was determined by Dilution Acacia plantations 2.00 (1.45)c 0.30 (0.84)a 0.316
plating technique using N-free Wakman’s medium 77 and Cardamom plantations 1.50 (1.19)d 3.20 (0.70)a 0.366
identified based on morphological, physiological and Coffee plantations 2.70 (1.62)b 2.10 (1.43)a 0.273
Paddy fields 0.06 (1.07)c 0.10 (0.77)b 0.376
cultural techniques.
Abundance of P- solubilizers was determined by F-test * *
standard plating technique using Sperber’s hydroxy Note: The values in the brackets are the transformed values using the square root transformation √ x +
0.5
apatite medium and identified based on the zone of
solubilization around them. Generic differentiation by Population of PO4- solubilizing bacteria in different land use types during pre and post-monsoon
morphological, physiological and cultural techniques. seasons
Population (cfuX103 g-1 soil) CD at 0.05%
Land use types
Pre-monsoon season Post-monsoon season
Natural forests 9.30 (2.60) a 2.20 (1.37) 0.65
Grasslands 2.00 (1.17) a 2.30 (1.14) 0.58
Acacia plantations 1.30 (1.07) a 1.80 (1.56) 0.563
Cardamom plantations 0.70 (0.95) c 0.80 (0.70) 0.171
Paddy Coffee plantations 1.40 (1.21) a 0.90 (1.01) 0.23
Paddy fields 1.20 (1.15) b 0.06 (0.77) 0.252
Study site
F-test at 0.05% * NS
Note: The values in the brackets are the transformed values using the sq
transformation √ x + 0.5
Coffee
CONCLUSION
Natural forests harboured higher population of Azotobacter and P-
Cardamom
solubilizing microorganisms.
Natural forest
The population of Azotobacter and P-solubilizing microorganisms
were higher in the pre-monsoon as compared to post monsoon.
50 m 50 m
6m
REFERENCES
3m
Acacia plantation
Raghuramulu, Y., 2001. Role of biofertilizers in coffee production.
50 m
Soil sampling procedure for microbiological analysis
Indian coffee, 65: 17-18
ACKNOWLEDGEMENT Sengupta, R. and Sengupta, C., 1992. Isolation of Azotobacter from
The authors are grateful to TSBF-CIAT/GEF/UNEP root and rhizosphere soil samples of local grasses and
for the financial support to carryout the investigation. detection of their phages from the natural ecosystem. Environ.
Ecol., 9:974-978.