World Journal of Agricultural Sciences 2 (1): 105-108, 2006
© IDOSI Publications, 2006
Corresponding Author: Dr. O.F. Owolade , The Institute of Agricultural Research and Training Moor Plantation, Ibadan, Nigeria
Phosphorus Level Affects Brown Blotch Disease, Development and Yield of Cowpea
O.F. Owolade, M.O. Akande, B.S. Alabi and J.A. Adediran
The Institute of Agricultural Research and Training Moor Plantation, Ibadan, Nigeria
Abstract: Application of Phosphorus in adequate concentrations could directly or indirectly reduce disease
incidence and severity of cowpea brown blotch and improve the forage and grain yield. A field experiment was
conducted to investigate the effects of level of phosphorus application on Brown Blotch disease of cowpea
(Vigna unguiculata [L.] Walp), caused by Colletotrichum capsici during 2003, 2004 and 2005 planting seasons.
Application of phosphorus was at 30, 60, 90 and 120 kg ha of P O . As P level increased numbers of petioles,
pods, nodules, seed/pod, leaf area and yield significantly increased. Disease incidence and severity of Brown
Blotch were significantly reduced at 90 and 120 kg ha of P O was not affected irrespective of the method of
application. Application method did not affect yield. Reduction in brown blotch disease at higher levels of P
Key words: Cowpea disease methods phosphorus rate
INTRODUCTION also influences the content of other nutrients in cowpea
Cowpea (Vigna unguiculata [L.] Walp) is an reported that P concentration in plant was highest
important grain legume in drier regions and marginal areas with the use of single super phosphate, as opposed to
of the tropics and subtropics. It is particularly important rock phosphate. The present study was undertaken to
in West Africa with over 9.3 million metric tons of annual determine effects of level and method of application
production . The grain is a good source of human of phosphorus on development, yield and severity of
protein, while the haulms are valuable source of brown blotch disease in cowpea.
livestock protein . Diseases of cowpea, induced by
species of pathogens, constitute one of the most MATERIALS AND METHODS
important constraints to profitable cowpea production
wherever it is cultivated. Among the fungal diseases, Field operation: Brown blotch infected seeds of Ife brown
brown blotch, caused by Colletotrichum capsici, is the variety of cowpea were collected from seed stored at the
most devastating with yield loss between 46 and 85% in Institute of Agricultural and Training, Ibadan. Nigeria.
Nigeria [3, 4]. Field experiments were conducted during 2003, 2004
Phosphorus fertilizer application has been observed and 2005 at the Institute of Agricultural and Training. The
to reduce rice blast disease . He stated that repeated site is located at Latitude 7°31'N and longitude 3°45'E and
application of phosphorus fertilizers delays the onset and 210 m above sea level in the forest-savanna transition
lessens the severity of take-all disease of barley just as agro-ecological zone of Nigeria. The field was laid out
potassium application reduces the disease incidence in in a Randomized Complete Block Design. The treatments
many cases probably by increasing phenolics synthesis consisted of four levels phosphorus (0, 30, 60, 90 and
in plants Calcium application also reduces bean root rot 120 kg ha of P O ) and two methods of application
caused by Rhizoctonia solani probably by altering (at planting or as a foliar spray).
pectin metabolism of the host . Therefore, application Three years before the experiment started, the plot
of mineral elements in adequate concentrations could had been cropped continuously to maize with no fertilizer.
directly or indirectly reduce disease incidence and The physicochemical properties of the field were analyzed
severity of crops. before cultivation in each of the three years, with P level
Phosphorus, although not required in large determined by the procedure of Leverty  (Table 1).
quantities is critical to cowpea yield because of its The land was plowed and harrowed twice. There were
multiple effects on nutrition and nitrogen fixation . It 27 plots (nine treatments replicated three times) of 25 m
leaves  and seed . Agboola and Obigbesan 
World J. Agric. Sci., 2 (1): 105-108, 2006
Table 1: Mean values of analyzed physicochemical properties of the soil of
the experimental site at Ibadan, Nigeria in years 2003, 2004 and
Soil characteristics 0-15 cm soil depth
Percent clay 5.2
Percent silt 9.8
Percent sand 85.0
Soil Texture Sand loam
pH (H O) 5.500
Organic carbon (%) 0.063
Total nitrogen (%) 0.070
Available phosphorus mg kg 0.870
CEC (meq/100 g soil) 3.390
Ex changeable bases (meq/100 g soil)
each, with 1 m paths across the rows and along the rows.
Four seed/hole were planted on 4 Sept. in each year were
planted at a spacing of 75 X 30 cm and thinned two-weeks
later to two plants/hole. At planting fertilizer was applied
to the side of the cowpea hill and foliar application was
done four weeks after planting. Weeds were controlled
with a mix of Gramozone® (paraquat dichloride: Jubaili
Agrotect Nigeria Limited) and Galex 500E® (metolachor +
metobromuron) (Novartis Nigeria Limited, Mushin,
Lagos, Nigeria) as a pre-emergent treatment at 2.5 L ha 1
with two hoe weeding at three and six weeks after planting
(WAP).The herbicides were applied at rate of 3 L ha 1
each using the Knapsack sprayer. The interior four of
seven rows per plot were used for data collection. The per plant (Table 3) was not significantly different among
insecticide Nuvacron® (Monocrotophos: Afcott Nigeria
Plc, Lagos, Nigeria) at the rate of 2 L ha using the
Numbers of petioles were counted and leaf area
measured at 50% pod formation, using a destructive
procedure from the plants in the rows next to the border
rows after the four interior rows, while numbers of pods,
nodules, seed/pod, 100-seed weight and yield were
assessed at maturity. Disease incidence was calculated
from the number of infected plants in the population.
The severity of brown blotch disease on pods on all
plants in the four interior rows was determined using
the visual assessment scale according to Alabi 
and modified: 0: no symptoms, 1: up to 20%; 2: 1-40%;
3: 41-60%; 4: 61-80% and 5: over 80% pods covered
with brown blotch.
Statistical analysis: The data were analyzed using the
general linear model (GLM) Statistical Analysis System
(SAS Inc., Cary, NC) at the 5% probability and means
separated using the Fishers Protected LSD test.
RESULTS AND DISCUSSION
The soil was very low in available P (0.87 mg kg ).
Table 2 shows the analysis of variance of the effect of the
different levels and method of application of P on yield
parameters and brown blotch disease of cowpea. The
results show that significant differences occurred among
the treatments irrespective of the parameters (p<0.05). The
influence of the environment was significant only on the
number of nodules per plant (Table 1). The number of
petioles per plant (Table 2) as well as the number of pod
the three growing seasons irrespective of the level and
method of application. However, the environment
significant influence the number of nodules when plants
Table 2: ANOVA table of the influence of levels and method of P application on yield components and brown blotch disease of Brown of cowpea
Per plant Disease
------------------------------------------------ Seed/ 1000 seed Leaf ---------------------------------
Sources Petioles Pods Nodules pod wt. area Incidence Severity Yield
method (A) 0.20 6.12* 4.56** 2.54 3.42 0.99 29.22* 1.98 17.23
P rate (P) 3.44** 13.22** 1.10 10.23** 6.56* 3.41* 52.35** 5.25** 65.33**
Year (Y) 0.43 0.89 0.82 2.58 3.33 1.20 16.25 1.88 17.52
A X P 2.33** 7.18* 13.77* 29.43** 3.86** 68.92** 18.16* 1.78** 47.98*
A X Y 0.01 0.05 0.55 2.75 1.45 1.47 3.89 0.36 6.20
P X Y 0.13 1.03 0.96 2.66 4.33 1.39 17.70 0.25 18.71
A X P X Y 0.19 0.71 0.88 0.86 1.93 0.05 6.90 2.05 13.25
Error 0.30 0.70 0.66 2.33 2.78 0.89 15.43 1.52 16.48
*, ** significant at p < 0.05 or p < 0.01, ANOVA
World J. Agric. Sci., 2 (1): 105-108, 2006
Table 3: Effect of levels and method of P application on yield components and brown blotch disease of Ife-Brown variety of cowpea
Application Phosphorus Petioles/ Pod/ Nodule/ Disease Disease Yield
method level (kg ha ) plant plant plant Seed/pod 100-seed wt. Leaf area incidence severity (kg ha )
30 29.22 50.23d 25.89d 12.82d 102.3b 20.56 66.33b 3.50b 993.85b
60 24.78 60.32c 36.00c 14.23bc 103.9b 24.11 26.11de 2.78b 1454.58a
90 26.67 69.67a 42.67b 16.78a 128.4a 26.33 24.89de 1.00c 1450.96a
120 27.44 75.12a 46.78a 16.88a 129.9a 27.67 21.67cd 1.00c 1482.11a
30 27.89 50.87d 26.33d 15.22b 105.4b 23.89 48.00c 2.00c 983.07b
60 24.44 58.22b 39.55c 15.34b 120.8a 26.88 30.33e 2.00c 1431.96a
90 26.56 69.00a 42.21b 17.12a 130.5a 26.77 29.11d 1.00b 1462.50a
120 32.66 73.78a 47.56a 17.22a 137.1a 26.78 25.44de 1.00b 1498.08a
control 0 12.44 25.22e 19.44e 12.56d 85.5c 18.88 80.11a 4.2a 647.74c
Values followed by the same letters are not significantly different Fishers Protected LSD test (p<0.05)
were sprayed with 30 kg ha and 120 kg ha with both of method of application. However, foliar application of
application methods. There were also no significant 120 kg ha of P gave the maximum 1000-grain weight
variations in the effect of the phosphorus fertilizer among (137.10 g), while the control gave the lowest 1000-grain
the three growing seasons on the number of seeds per weight of 85.5 g. The results indicated that all the
pod leaf area (cm ) 100-seed weight and yield kg ha . The fertilizer treatments gave significantly higher yield as
application method by phosphorus rate interaction (A x P) compared to control. Table 3 also showed that P
were significant for all the growth parameters (p<0.05) just application significantly increased the grain yield of
as it influenced significantly (p<0.05) the incidence and Ife-Brown cowpea variety compared with the
severity of brown blotch of cowpea. The application recommended 30 kg ha and the control. However,
method by year interaction (A x Y) just as phosphorus among the fertilizer treatments, foliar application of
rate by year interaction was not significant for all the 120 kg ha of P produced the highest grain yield
parameters as well as for disease incidence and severity (1493.07 kg ha ). The results in Table 3 also show that
(Table 2). The results in Table 2 also showed that the application of P at 90 and 120 kg ha irrespective of
application by phosphorus rate by year interactions method of application reduced the incidence and
(A x P x Y) was not significant The results in Table 3 show severity of brown blotch disease significantly. The
that significant differences did not occur among the levels highest disease incidence and severity were observed
P irrespective of the method of application on the number with control.
of petioles. However, the number of petioles in these The significant response of cowpea variety to P
treatments was significantly higher than in the control. application in terms of growth parameters, grain yield and
The maximum number of petioles 32.66 was recorded when reduction in the incidence and severity of brown blotch
the plant was sprayed with 120 kg ha of P. Application disease is an indication that P is an important nutrient
of higher doses of P significantly increased the number of element influencing the performance of cowpea plant on
pods/plants and nodules/plant irrespective of method of the field. Tenebe et al. , Ankomah et al. , just as
application. The highest number of pods (75.12) was Okeleye and Okelana , observed significant
obtained when the crop received 120 kg ha of P fertilizer increase in nodulation, grain yield, total dry matter,
applied basally while, the maximum number of nodules of numbers of flower, pods and seed per plant for
47.56 was recorded when the same quantity of P was cowpea varieties in response to P application. The
sprayed on cowpea. Application of higher doses P increase in nodulation observed in this study
increased the leaf area compared to the control but all the contradicts the findings of Kolawole et al. , which
treatment were statistically at par with each other. The reported a decrease in number of nodules due to
number of seeds per pod increase significantly with increase in P application, but agrees with the results
increase in the levels of P fertilizer. There were however, of Luse et al. , Agboola and Obisesan  and
no significant differences in the number of seed per pod Ankomah et al. . The observed increase in cowpea
between the control and basal application of 30 kg ha of grain yield due to increase in level of P in the present
P. Foliar spray of P at 120 ka ha gave the highest study is in consonance with the results reported by
number of seed per pod (17.22), while the control Tenebe et al. , Ankomah et al.  and Kolawole et al.
experiment gave the lowest seed/pod of 12.56. The data in , but disagrees with the results obtained by
Table 3 revealed a significant increase in 1000-grain Agboola and Obigbesan  and Osiname , who did
weight with increase in the concentration of P irrespective not observe significant effect of on the yield of cowpea
World J. Agric. Sci., 2 (1): 105-108, 2006
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