EFFECTS OF FERTILIZERS AND HERBICIDES ON THE REACTION OF COWPEA VARIETIES (Vigna unguiculata (L.) Walp.) TO Alectra vogelii (Benth.)
EFFECTS OF FERTILIZERS AND HERBICIDES ON THE REACTION OF COWPEA VARIETIES (Vigna unguiculata (L.) Walp.) TO Alectra vogelii (Benth.)
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Date
1994-07
Authors
MAGANI, ENOCH ISTIFANUS
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Abstract
Field and green house trials were conducted to study the
effects of fertilizers and herbicides on the reaction of cowpea
varieties to Alectra voqelii (Benth.) at Samaru in the northern
Guinea savanna ecological zone of Nigeria in 1991 and 1992 wet
seasons and the reaction of cowpea varieties to Alectra seed
concentration in the green house in 1992 and 1993 dry seasons.
Cowpea variety B 301 and the derivatives of its crosses
with IT84 S-2246-4 (IT 90 K-59 and IT 90 K-76) did not support
Alectra emergence. The varieties also produced cowpea grain
yields that were comparable to the maximum in the 1991 trial and
significantly higher than the least in the two years. The
nodulation of these varieties were however reduced in the pot by
21.57%, 43.9 and 76.9%. for B 301, IT 90K-59 and IT90K-76,
respectively. However, IT 89 KD-245 and IT 89KD-245-1, both of
which are derivatives of B 301 and local variety Kananado
supported low emergence of Alectra. Inspite of high reduction of
nodulation in the pot by Alec tra and support for low Alectra
infection in all the trials, IT86D-534 did not suffer any
reduction in cowpea grain yield in two field trials. Inspite of
high infestation by Alectra and very low pod number Kano 1696
still produced acceptable grain yield. Cowpea varieties IT82D-849
and SUVITA-2 known to be resistant to Striqa qesnerioides,
exhibited susceptibility to Alectra. Both TVx 3236 and SAMPEA 7,
supported high Alectra infection with consequent high
susceptibi1ty to the parasite in the field. In the green house
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TVX 3236 initiated early emergence of Alectra and had more number
of emerged Alectra compared with all the other varieties. Under
artificial inoculation, all the varieties tested, including B
301, produced lower grain yield than VITA-3, the only variety in
which Alectra infection did not cause cowpea grain yield
reduction in 1992.
In the evaluation of nitrogen and phosphorus combinations on
the reaction of cowpea varieties to Alectra voqeli i , cowpea
varieties TN93-S0 and IT89KD-245-1 significantly delayed Alectra
emergence compared with VITA-3 and SAMPEA-7 in 1991 and 1992,
respectively. Inspite of higher number of plants infected and
Alectra shoot count, VITA-3 still produced cowpea grain yield
comparable to the maximum tined by IT 89 KD-245-1 in 1992.
Phosphorus application at 20 kg P/ha significantly increased
cowpea grain yield without any significant effect on Alectra
incidence. Nitrogen application at 60 kg M/ha consistently
reduced the number of plants infected and Alectra shoot count,
but resulted in cowpea grain yield depression compared with 0 and
30 kg N/ha. It was apparent from the 2-order interaction, that
varieties which exhibited moderate (TN 93-80 in 1991) to high
(IT89KD-245-1 in 1992) resistance responded to high doses of N
(60 kg/ha) and P(40 Kg P/ha) by delaying the emergence of
Alectra.
In the two years, pre-emergence herbicide applications
the mixtures containing Pree (metazachlor + antidote) followed by
imazaquin at 0.18 kg a.i./ha resulted in significantly lower
number of plants infected. Similarly, in 1991, Pendimetha1 in
plus imazaquin at 0.87 + 0.15 and 1.09 + 0.19 kg a.i/ha and
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pendimethalin plus imazethapyr at 1.58 + 0.12 kg a.i/ha, all
followed by imazaquin at 0.18 kg a.i/ha, resulted in lower number
of cowpea plants infected by Alectra compared with the weedy
check. In 1992, post-emergence application of Pree plus
imazethapyr at 1.0 + 0.075 kg a.i/ha resulted in lower number of
infected plants compared with the maximum obtained with
pendimenthalin plus imazaquin at 1.09 + 0.19 and pendimethalin
plus imazethapyr at 1.58 + 0.12, both followed by SHW which also
resulted in significantly higher cowpea grain yield than the
weedy check.
In the green house, the reaction of cowpea varieties to preconditioning
and concentration of seed inoculant of Alectra
voqelii indicated that Alectra emergence increased wih Alectra
seed concentrations in the first trial, while lOc.c/pot Alectra
seed gave the highest number of emerged Alectra with compared to
other Alectra seed concentrations in the second trial. Preconditioning
period had no significant effect on number of days
to Alectra emergence but Alectra emergence increased with preconditioning
period of 7 and 14 days.
Description
A thesis subnitted to the Postgraduate School, Ahnadu Bello
University, Zaria in partial fulfilment of the requirement for
the Degree of Doctor of Philosophy in Agronomy.
DEPARTMENT OF AGRONOMY
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
EFFECTS,, FERTILIZERS,, HERBICIDES,, REACTION,, COWPEA VARIETIES,, (Vigna unguiculata (L.) Walp.),, Alectra vogelii ,, (Benth.),