Agriculture Reference
In-Depth Information
each source for 52 weeks from May 2003 to April 2004. In all, six were
involved - stream, shallow well and piped irrigation water sources in Kumasi
and drain, stream and piped water in Accra. Sampling at all sites was carried
out between eight and ten in the morning in keeping with farmer's irrigation
practices (APHA/AWWA/WEF, 2001). At each site, 200-ml glass bottles were
used to take water from three different points in the wells or in 20-m intervals
along the drain or stream. Piped water was collected directly from the water
hose used by the farmers for irrigation. Samples from a particular site were
later joined into one composite sample per source and transported to the
laboratory on ice. A total of 312 composite water samples were analysed for
total and fecal coliform populations. Sampling for helminth egg quantification
in irrigation water was done twice every month for five months from
November 2003 to March 2004 at all the selected sites. Two-litre samples
were taken after deliberately disturbing the bed of the irrigation water source
to stimulate agitation that might occur when farmers are filling their watering
cans. This was intended to bring out the eggs, as they usually settle under
their own weight (Cornish et al, 1999).
Lettuce sampling in farms, wholesale and retail markets
Over a period of 12 months, from May 2003 to April 2004, a total of 1296
lettuce samples were collected at different entry points
2
from farm to the final
retail outlet. The original sets of lettuce were either irrigated with stream,
drain, well or piped water (microbiological quality of these water sources
were monitored as described above). Twice a month, a minimum of three
composite samples (each containing two whole lettuces) from each of the
selected farm sites were randomly collected using sterile disposable gloves just
before harvesting for sale at the market. These were put into separate sterile
polythene bags and labelled as farm samples. The seller was followed to the
wholesale market where another sample from the same original stock was
collected, before being finally sold to a retailer. At the final retail point, three
composite samples were again sampled after vegetables were displayed on the
shelves for at least two to three hours, which is a typical turn-over period at
the retail point. Producers and sellers were paid for their produce. Sampled
vegetables were transported on ice to the laboratory where they were analysed
for TC, FC and helminth counts. To eliminate potential biases during
analysis, staff working in the laboratories were blind to the source of the
samples.
Phase III: Field trials
In order to further understand the importance of the different possible sources
of contamination of irrigated lettuce (e.g. wastewater, poultry manure, soil), a
field trial was set up at two farm sites in Accra. Lettuces were grown on raised
beds of the common size of approximately 3m
2
. For each trial two adjacent
plots, A and B, were used, with each plot subdivided into four blocks. Each
block contained four beds, making a total of 16 beds per plot. Using a
