Effects of timing and frequency of leaf harvesting on leaf and seed yields of selected lines of cowpea (vigna unguiculata) in Morogoro, Tanzania
No Thumbnail Available
Date
2009
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
Cowpea [F7gna unguiculata (L.) Walp.J is consumed both as grain and as a vegetable. 1
practice, in East and West Africa the vegetable leaves are harvested from the same cro[.
planted for seed production. The timing of leaf removal and subsequent frequency of the
harvesting have great effects on the cowpea plant’s ability to recover from defoliation.
An experiment was conducted at the horticulture unit of Sokoine University of
Agriculture in Morogoro, Tanzania, to establish threshold levels at which timing and
frequencies of leaf harvesting can be combined for optimal leaf and seed yields. Four
cowpea lines (Vuli, UG-CP-9,1T97K10687 and Ngoji) were used as main plots in a split
split plot design experiment where time to start leaf harvesting (20, 30 and 40 days after
planting) was sub-plot treatment and harvesting frequencies of as per appearance, once a
week, once in two weeks and no harvesting were sub-sub plots. The experiment was
planted during the short rains season between September 2007 and January 2008. Data
were collected on leaf yield, vegetative growth and seed yield. Harvesting as per
appearance gave highest leaf yields but lowest seed yields. Delaying time to start leaf
harvesting increased seed yields at the expense of leaf yield. Line Ngoji produced more
leaves and had higher leaf yields than the other lines, but its seed production was low. In
this study, the threshold level at which combined leaf and seed yields, with high enough
proportion of seed yield of about 45% or more, was when time to start leaf harvesting
was 30 days from planting with harvesting frequency once a week. When the threshold
-2^jwel criterion was to achieve the highest combined leaf and seed yields, the best
—nbination was harvesting at 30 DAP with frequency as per appearance except for line Vuli. With a threshold of monetary equivalent the best combination was when time to
start leaf harvesting was 30 days from sowing (T30) with harvesting frequency as per
appearance. It has been established also, however, that suitable timing to begin leaf
harvesting and frequency of leaf harvesting for optimized leaf and seed yields is
cultivar-specific.
Description
Dissertation
Keywords
Leaf harvesting, Seed production, Africa vegetable, Cowpea (vigna unguiculata), Morogoro, Tanzania