INFLUENCE OF MICROBIAL CULTURES AND ORGANIC MANURE ON LEAFY VEGETABLES GROWN IN POLLUTED SOILS AND POLLUTED WATER
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Date
2018
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PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
The experiment was conducted during 2016 -17 at Department of Agricultural
Microbiology and Bioenergy, College of Agriculture, Rajendranagar, PJTSAU, Hyderabad.
Heavy metal pollution is currently a major environmental problem because metal
ions persist in the environment due to their non-degradable nature. The toxicity and
bioaccumulation tendency of heavy metals in the environment is a serious threat to the
health of living organisms. Bioremediation is a state-of-the-art technique used for heavy
metal removal or recovery from polluted environments. The technique utilizes inherent
biological mechanisms to eradicate hazardous contaminants using microorganisms and
plants, or their products. Microorganisms are omnipresent that dominate in heavy metalcontaminated soil and can easily convert heavy metals into non-toxic forms.
A total of 28 isolates were collected from different polluted sites of Hyderabad
where green leafy vegetables were grown. The isolates were screened for their PGPR
properties, the isolates were also tested for their heavy metal tolerance. The best five
potential heavy metal tolerant PGP bacteria were studied for their molecular identification
and were identified by 16S rRNA gene sequencing. BLAST search through NCBI revealed
97 % similarity of SfS-5 with Bacillus megaterium, 98 % similarity of AfS-8 with
Pseudomonas aeruginosa, 98 % similarity of SfS-18 with Rhizobium meliloti, 99 %
similarity of SfS-24 with Azotobacter chroococcum, 97 % similarity of SfW-28 with
Azotobacter chroococcum.
An experiment entitled “Influence of microbial cultures and organic manure on
leafy vegetables grown in polluted soil and polluted water” was conducted in pot culture
with 14 treatments and three replications during Rabi, 2016 and Rabi, 2017. The crops
grown were spinach and coriander and seed treated with nitrogen fixer (SfS -24) and
phosphate solubilizer (AfS - 8). The treatments imposed were T1: (Control- without
fertilizers), T2: (Soil + Water + Biofertilisers), T3: (Soil + water + OM), T4: (Soil + water
+ RDF), T5: (Soil + water + Biofertilisers + OM), T6: (Polluted Soil+ water +
Biofertilisers), T7: (Polluted Soil+ water + OM), T8: (Polluted Soil+ water + RDF), T9:
(Polluted Soil+ water + Biofertilisers + OM), T10: (Soil + Polluted water + Biofertilisers),
T11: (Soil + Polluted water + OM), T12: (Soil + Polluted water + RDF), T13: (Soil +
Polluted water + Biofertilisers+ OM), T14: (Sterilized soil - control). The influence of
various inorganic fertilizers, organic fertilizers and biofertilizers on plant height, root
length, fresh weight and dry weight, available NPK, soil enzyme, soil microbial population
was recorded at 20, 40, 60 DAS of the crop. The number of leaves and yield were
determined. The concentrations of macro and micronutrients in plant at harvest were
estimated.
At the time of Harvest, highest plant growth parameters, dry matter accumulation,
number of branches per plant, number leaves per plant yield were recorded in the treatment
which received 100 % RDF (T8: Polluted Soil+ water + RDF). Plant height at 60 DAS was
found highest in T8 with 30.4 cm in spinach and 45.4 cm in coriander; fresh weight at 60
DAS was registered significantly highest in T8 with 30.4 g in spinach and 11.0 g in
coriander. Soil biological quality was high in treatments supplied with biofertilizer along
with organic manure application. Bacterial population count was enumerated and found to
be significantly highest in T9: Polluted soil + water + Biofertilisers + OM with 101.1 ×
107 CFU g
-1
of soil with spinach and 92.1 × 107 CFU g
-1
of soil with coriander at 60 DAS ,
Similarly, soil enzyme activity (dehydrogenase, urease and phosphatase) was significantly
higher in treatment T9 for both the crops at the time of harvest.
Higher heavy metal concentration in the soil was recorded in pots irrigated with
polluted water (T10, T11, T12 and T13) with increasing concentration of available NPK.
The heavy metal concentration was recorded significantly higher in T12: Soil + Polluted
water + RDF (Ni-4.084, Cd-1.573, Co-1.789 and Pb-13.850 mg kg-1
) in spinach grown soil,
whereas, in coriander grown soil was (Ni-3.72, Cd-2.143, Co-0.830 and Pb-9.65 mg kg-1
).
With increase in soil heavy metal content, the accumulation in plant also increased but with
decrease in soil microbial population and enzyme activity. Significantly lower levels of
heavy metal concentration in both plant shoot and soil was observed in the treatments
receiving biofertlisers and organic manures, among all T9 is the treatment showed highest
removal even though its initial heavy metal concentration was high.
Based on the results obtained in the present study, it is observed that the consortia
of heavy metal tolerant PGPR bacteria with soil application of FYM can serve as cost
effective, ecofriendly bioremediating source in heavy metal polluted urban areas.
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D10,349