EFFECT OF ROW SPACING AND WEED CONTROL ON THE PERFORMANCE OF SOYABEAN (Glycine max (L.) Merrill) IN THE NORTHERN GUINEA SAVANNA OF NIGERIA
EFFECT OF ROW SPACING AND WEED CONTROL ON THE PERFORMANCE OF SOYABEAN (Glycine max (L.) Merrill) IN THE NORTHERN GUINEA SAVANNA OF NIGERIA
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Date
1998-07
Authors
SHEBAYAN, Joseph Akimbo Yusufu
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Abstract
Field trials were conducted in 1984 - 1988 wet seasons at
Samaru in the northern Guinea savanna zone of Nigeria to study
the response of soyabean (Glycine max (L.) Merrill) sown at
inter-row spacings of 45, 60, 75 and 90cm to various periods
of weed interference and to determine how best to control
weeds in soyabean using a recommended herbicide.
Inter-row spacing of 45cm resulted in significantly lower
weed cover score and cumulative weed weights than 75 and 90cm
in all years, and had higher ground cover and taller plants
than 75 and 90 cm inter-row spacing, however, the grain yields
were not influenced by row spacing.
In the weed interference study, initial weed infestation
of soyabean for only 3 WAS did not have a significant effect
on any of the crop growth parameters and soyabean grain yield
provided the weeds were subsequently removed. However weed
infestation beyond 6 WAS significantly depressed crop vigour
score, plant height, number of branches per plant as well as
number of pods per plant, number of grains per pod, 1000-grain
weight and grain yield compared with the crop kept weed - free
throughout its life cycle.
To obtain soyabean grain yield comparable to that
obtained in the plot kept weed - free till harvest it was
necessary to keep the crop weed-free for the initial period of
6 WAS and later.
In the weed control trials the use of herbicides and hoeweeding
always resulted in significantly lower weed cover
score and weed dry matter production compared with the weedy
check. In addition supplementary hoe-weeding significantly
reduced weed cover score, weed dry weight at harvest and
cumulative weed dry weight than the weedy check but comparable
to the hoe-weeded control in all years except in 1984. Each
herbicide rate supplemented with one hoe-weeding resulted in
lower weed score and weed dry weight than its corresponding
rate not supplemented with a hoe-weeding but comparable to the
hoe-weeded control. Except in 1984, when Galex at 1.5kg
a.i/ha gave higher weed dry weight at harvest than Galex at
3.0kg a.i/ha, there were no significant differences in weed
dry weight at harvest between both rates of the herbicide.
Soyabean in the herbicide treated plots gave higher
vigour scores, percent ground cover, number of branches per
plant, number of pods per plant, number of seeds per pod and
1000 grain weight than the unweeded check. The hoe-weeded
control was comparable to the best herbicide treatment in
these parameters. Galex at 3.0kg a.i/ha followed by SHW gave
the highest grain yield but was comparable to the hoe-weeded
control and Galex at 1.5kg a.i/ha followed by SHW.
In this study, uncontrolled weed growth throughout the
crop life cycle resulted in 55.0 to 73.0% reduction of
soyabean grain yield compared with the maximum obtained in the
trial soyabean grain yield was positively correlated with
soyabean stand count, plant height, ground cover, number of
branches per plant, pods per plant, grains per pod and 1000-
grain weight and negatively correlated with weed dry weight.
In the path analysis and the percentage contribution study
number of pods per plant made the highest individual
contribution to grain yield followed by 1000-grain weight
Description
A Dissertation submitted to the Postgraduate School
Ahmadu Bello University, Zaria, In fulfillment of the requirements
for the degree of Doctor of Philosophy in Agronomy
DEPARTMENT OF AGRONOMY
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY, ZARIA
JULY, 1998
Keywords
EFFECT,, SPACING,, WEED,, CONTROL,, PERFORMANCE,, SOYABEAN,, (Glycine max (L.) Merrill), NORTHERN,, GUINEA,, SAVANNA,, NIGERIA.