Agriculture Reference
In-Depth Information
McConkey, putative enterobacteria and nutrient agar (NA) heated to 80
°
C
for 30 min, spore-forming bacteria. All plates were incubated at 28
°
C.
Bacterial genetic diversity
Genetic shifts within bacterial communities in both plots were examined
using ERIC-PCR (enterobacterial repetitive intergenic consensus-
polymerase chain reaction) fingerprinting of bacteria (de Bruijn
et al
.,
1992). ERIC-PCR fingerprints tend to be strain specific and indicate diver-
sity at a sub-species level. The population chosen for analysis, selected on
PSA medium, was an agriculturally important group implicated in healthy
plant growth, i.e. the fluorescent pseudomonads. All colonies isolated were
fingerprinted and analysed. The bacterial ERIC-PCR fingerprints were
run on the ABI DNA Sequencer system using Genescan™ software and
analysed via the Microsoft Access database program. This program
converts the ERIC-PCR fingerprint data into a suitable format so that
the bacterial isolates can be compared, and assigned into groups. The
PHYLIP Version 3.57 software package UPGMA (Unweighted Pair
Group Method using Average linkage; Felsenstein, 1996) was used to
display the relationship between the bacterial isolates.
Results and Discussion
Both Sewage and FYM sites have similar C and N contents (Table 5.3.1),
and the C : N ratios are 11.2 and 11.5, respectively. The levels of heavy
metals are greater in the Sewage-treated plot compared with the FYM plot
(Table 5.3.1) with respect to all the metals tested, although all values
(except cadmium) are below the UK limits.
Analysis showed these soils to be similar in all respects except for the
heavy metal content resulting from the past sewage sludge applications.
Table 5.3.1.
Percentage carbon, nitrogen and heavy metal content (p.p.m.) of soils. All errors are
±
standard deviation in parentheses after the mean.
Element
Sewage
FYM
Element
Sewage
FYM
UK limits
%N
0.185 (0.002)
0.163 (0.001)
Zinc
234.1 (0.79)
94.5 (1.1)
300
Copper
69.70 (0.52)
22.7 (0.25)
135
%C
2.141 (0.031)
1.821 (0.011)
Nickel
23.90 (0.36)
14.6 (0.32)
75
Cadmium
6.35 (0.03)
1.44 (0.15)
3
Chromium
99.10 (1.20)
43.5 (0.50)
400
Lead
75.90 (0.52)
34.5 (0.59)
300
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