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A STUDY ON MICROBIAL POPULATION DYNAMICS IN SOILS GROWN WITH Bt COTTON

KrishiKosh

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Title A STUDY ON MICROBIAL POPULATION DYNAMICS IN SOILS GROWN WITH Bt COTTON
 
Creator TEJASHREE, M
 
Contributor SUBHASH REDDY, R
 
Subject cotton, enzymes, bacteria, land resources, crops, herbicides, sampling, inorganic compounds, soil sampling, maize
 
Description Cotton cultivation in India covers an area of approximately 9 million hectares
representing about one quarter of the global area of 35 million hectares under cotton.
Cotton is planted by 4 million small farmers and involves many more farmers in
processing, textile manufacturing and trade. In India the average production is about
16 % of the world production and this decrease is due to the susceptibility of cotton
to the 162 species of insects. Cotton bollworms are the most serious pests. Further,
the most destructive pest, Helicoverpa armigera is known to develop resistance
against the most of the recommended insecticides which force the farmers to apply as
many as 10-16 sprays. In India, efforts were made to harness genetic engineering
technology for bollworm resistance in cotton which led to the development of the Bt
cotton by transferring the cry gene from the soil bacterium Bacillus thuringiensis sub
species kurstaki (Bt) which produces a protein toxic to bollworm thus providing
resistance to plants and significantly reducing the need for applications of chemical
insecticides.
Concerns have been raised about the environmental risks associated with the
release of transgenic Bt cotton produced a potential impact on non-target organisms,
such as beneficial insects, soil bacteria, and fungi, which play a fundamental role in
crop residue degradation and in biogeochemical cycles. In fact, many studies showed
that soil microbes represent important key non-target organisms able to highlight
unforeseen collateral effects of transgenic plants on natural and agricultural
ecosystems.
Hence this current field study was conducted under two experiments to study
the impact of the Bt cotton, one was conducted in the farmers’ field where the non Bt
cotton and Bt cotton were cultivated for particular number of years viz., 2 yr, 4 yr and
10 yr. The soil collected from such fields were analyzed for biological parameters
like microbial counts, soil enzymes like dehydrogenase, phosphatase and urease were
estimated and soil microbial biomass. Non Bt cotton has showed significantly higher
microbial activities than the Bt cotton cultivated field. A significant decrease was
seen from the field cultivated with Bt cotton for 2 yr, 4 yr and 10 yr. Lowest activity
was noticed in the Bt cotton field cultivated for 10 yr.
In another experiment, the soil samples were collected from college farm,
Rajendranagar (ANGRAU) from fields cultivated with Bt cotton, non Bt cotton, red
gram and maize crops. Bt cotton was found to have significantly lower microbial
activity than non Bt cotton. Higher microbial activities were recorded in maize and
red gram crops. In the same experiment Bt cotton was also compared with the
treatments which were treated with different herbicides viz., pyrithiobac sodium,
pendimethalin and pyrithiobac sodium + quizalofop. The results of Bt cotton and Bt
cotton + pendimethalin were comparable. Microbial activities significantly effected
in the treatment with Bt cotton + pyrithiobac sodium + quizalofop.
The biological parameters like microbial counts, soil enzymes like
dehydrogenase, phosphatase and urease were estimated and soil microbial biomass.
Soil enzymes were included as they play a key biochemical functions in overall
process of organic matter decomposition in the soil system. Their levels also vary
with different types of soil and their organic content, activity of the microbes and
intensity of the biological processes. Microbial biomass is also considered as
measure of the response of the soil micro biota. Therefore these parameters were
used in the following investigation done on Bt cotton to find effect on soil health
 
Date 2016-06-13T12:12:03Z
2016-06-13T12:12:03Z
2013
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/67259
 
Language en
 
Relation D9311;
 
Format application/pdf
 
Publisher ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY