Agriculture Reference
In-Depth Information
randomized complete block design, each of the four beds in a block was
randomly allocated to one of four treatments (three representative poultry
manure samples, PM
1
,PM
2
and PM
3
, with average FC populations of
4
:
3
10
7
,2
:
4
10
5
and 3
:
3
10
3
100 g
1
, respectively, and one inorganic
fertilizer NPK (F)), which were applied to the beds two weeks after
transplanting following farmers' usual practices. Each of the two plots (A and
B) at a site was irrigated with either clean piped water or wastewater from a
drain. The crops on a bed were irrigated once daily with approximately 30 l of
water every morning excluding rainy days. All work was done by the farmers
as part of their standard routine.
Soil samples from the top 10 cm were collected from six randomly selected
points on each bed, just before transplanting from the nursery, and combined
into one composite sample per bed for the initial count of FC and helminth egg
populations in duplicates. Samples were also taken from nearby plots with no
previous history of vegetable production to serve as controls. Six lettuce heads
were aseptically collected from each bed four weeks after transplanting, after
which they were randomly combined into three composite samples containing
two lettuce heads. The samples were kept in a refrigerator at 48C and analysed
within 24 hours for FC and helminth eggs using standard methods.
Data analysis
The data were analysed using SPSS for Windows 10. Using MPN, FC
populations were normalized by log transformation for the analysis of
variance (ANOVA). t-tests, used to compare data sets, were also employed
where necessary. Inferences for significant differences were set at P
<
0
:
05.
R
ESULTS AND
D
ISCUSSION
Microbiological quality of market vegetables from
urban markets
Bacterial contamination of market vegetables
Most of the vegetable samples showed high FC contamination levels (see
Table 6.1). The highest level of FC contamination was recorded in lettuce
(geometric mean count of 1
:
1
10
7
per g wet weight), probably due to the
Table 6.1 Ranges of total and fecal coliform population on selected vegetables
MPN g
1
wet weight
Vegetable
Total coliform
Fecal coliform
9:3 10
5
to 1:5 10
11
4:0 10
3
to 9:3 10
8
Lettuce
2:6 10
5
to 1:5 10
11
1:4 10
4
to 2:8 10
7
Cabbage
9:3 10
5
to 1:9 10
10
1:5 10
4
to 4:6 10
8
Spring onion
Note: MPN, most probable number.
