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A field experiment was conducted at Sri
Krishnadevaraya University, Anantapuramu, India to study the
population of bacteria in groundnut soil. Most important annual oil
seed crop is the groundnut. The yield of crop depends on various
agronomic management practices. The groundnut bacterial composition
in the rhizosphere is important for the performance of plant as
bacterial species can
have beneficial, neutral, or harmful relationships with the roots.
Bacteria are important in process such as nitrification,
denitrification, and nitrogen fixation. Soil bacteria play an
important role in the global cycling of carbon and other elements.
Soils containing a high microbial diversity are characteristic of a
healthy soil-plant relationship. Soil samples (red sandy loam and
black clay soils) were collected from groundnut (Arachis hypogaea
L.) cultivated fields of Anantapuramu District of Andhra Pradesh,
were treated with selected insecticides – bifenthrin, buprofezin and
fungicides-dimethomorph, pyraclostrobin at different concentrations,
that is, 10, 25, 50, 75, and 100 ppm which are equivalent to field
application rates (1.0, 2.5, 5.0, 7.5, and 10.0 kg/ha) in the
laboratory. Results of the study showed that the bifenthrin,
buprofezin, dimethomorph, and pyraclostrobin significantly improved
the bacterial population in 10 days incubated both red and black
soil samples. Bifenthrin and buprofezin at concentrations ranging
from 1.0 to 5.0 kg/ha gradually increased the population of bacteria
and reached maximum at 5.0 kg/ha. Beyond 5.0 kg/ha the above
pesticides shown negative effect on bacterial population at 10.0
kg/ha, whereas the bacterial population had decreased at
concentration of 7.5–10.0 kg/ha. Whereas dimethomorph and
pyraclostrobin at the concentrations of 1.0 and 2.5 kg/ha showed
marked increase in bacterial populations, and beyond this
concentration the bacterial population reached minimum at 10.0 kg/ha
in both black and red soils.
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