Agriculture Reference
In-Depth Information
nematodes present) and replicated four times. The six soil treatments were
prepared with potting mixture and the following fresh-weight percentages of
compost: 0, 6.25, 12.5, 25, 50 and 100 per cent. For each vegetable, two
three-week-old seedlings were transplanted into a half-litre pot containing a
different soil treatment. Into half of the pots, a 1-ml aliquot of nematode egg
suspension, prepared using established methods, was injected into the soil
1 cm from the seedlings. Pots were kept in a screenhouse for six weeks, with
temperatures ranging between 25 and 308C, and watered every two days to
maintain sucient moisture. At harvest, plants were uprooted and shoot,
root lengths and fresh weights determined. The incidence and severity of
nematode root-galling was rated using a five-point scale.
Field fertilizer experiment
Two field experiments were conducted with the farmers of the Gyenyasi
Farmers Cooperative. This cooperative has about 16 farmers, who produce
lettuce, cabbage and spring onions in a 2-ha plot. Fourteen raised lettuce beds
belonging to three farmers were divided into 30 plots, with sizes ranging
from 7.5 to 12m
2
. The fertilizer treatments included the compost and poultry
manure applied at rates of 1, 2 and 4 kgm
2
on each crop for three crops,
compost applied at 2.5, 5 and 10 kgm
2
on the first crop, and a control with
no compost applied.
The first experiment compared the compost and poultry manure
applications on three crops. Since farmers evaluate the impact fertilizers
based on how much they have to carry into the field, the two fertilizers were
compared on a weight basis and not a nutrient basis. The second experiment
compared lettuce yields over three harvests from a single application of
compost to the first crop. Lettuce plants were watered daily with
approximately 6 l m
2
of irrigation water containing about 28mg N l
1
. The
equivalent fertilization was about 50 kgNha
1
per month. Hand weeding
was done on the same day each week and no pesticides were applied on the
first crop. An outbreak of septoria leaf spot (Septoria lactucae Pass.) in the
second and third crops required the use of Dithane fungicide. Composite soil
samples were taken for chemical analyses and bulk density determined from
each plot at the beginning of the experiment and after each cropping season.
The fresh yield of all lettuce plants within a 1-m
2
grid was determined four
weeks after transplanting.
Statistical analysis
Descriptive and inferential statistical tools were used to analyse interview
data using SPSS software. The data from the CVM survey were analysed
with a probit model. Correlations and means comparisons were conducted
for the different explanatory variables to avoid multi-colinearity in the probit
model. Due to di
culties in obtaining su
cient materials and labour, the
germination experiment was not replicated and only one experimental unit
per
treatment was available. The unreplicated data were analysed by
