| dc.description.abstract | Two experiments were conducted at the field station of. the
Faculty of Agriculture, University of Nairobi, between July 1988 and
April 1989 to show the effects of N application on plant growth,
yields, quality and shelf-life of pods of French beans (Phaseolus
vulgaris L.).
The bean plants of Monel variety were topdressed with N at 0,
26, 52 and 78kg/ha and data on dry matter accumulation in leaves,
stems and nodules, days to 50% flowering, total and marketable
yield, quality and shelf-life of the pods were collected. Freshly
harvested pods were analysed for crude protein, total ash, crude
fibre, nitrates, ascorbic acid and chlorophyll.
For storage study, freshly harvested pods were separated into
fine and extra fine grades and stored in 1kg lots in fibre board. cartons
at 40C and at room temperatures (23 ± 10C and 25 ± 10C in the first
and second experiments respectively). During storage the pods were
analysed for weight loss, withering, percent retention of ascorbic
acid, and chlorophyll contents and chilling injury for those stored at
40C.
Nitrogen application significantly increased the dry matter of the
leaves sampled at the bloom and pod stages in the first experiment
(first season). Application of 26kgN/ha effected the greatest increase
on the dry matter content of the leaves sampled at bloom stage
while at pod stage, 52kg/ha effected the greatest increase. The latter
rate also had the greatest increase on the accumulation of dry matter
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in the stems. The dry matter yield in the nodules was significantly
lowered by N top-dressing.
Days to 50% flowering were not significantly affected by N
application.
Nitrogen application had no significant effect on the total and
marketable pod yields but, in the second season, the topdressed
plants yielded significantly more reject grade pods than those that
were not.
The effects of N on crude protein, total ash, crude fibre and
nitrate contents were not significant although N tended to increase
the crude protein and nitrates and to decrease the total ash and fibre
contents.
Weight loss, withering and retentions of ascorbic acid and
chlorophyll during storage were not significantly affected by
nitrogen application. Judged from the extent of withering the extrafine
and fine grade pods had a shelf life of two and three days
respectively at room temperatures, while judged by the extent of
chilling injury the shelf-life of the two grades was also limited to
two and three days respectively at 40C. Storage conditions had a
significant effect on losses of ascorbic acid and chlorophyll. The
losses were generally higher from pods stored at room temperatures
than from pods stored at 40C. | en |
