Growth and yield parameters of three cowpea

AUTHORS:
Nonkululeko Mfeka1
(Vigna unguiculata L. Walp) lines as affected by
Reckson A. Mulidzi2
planting date and zinc application rate
Francis B. Lewu1

AFFILIATIONS: Cowpea is one of the most important food legumes in most African countries. Cowpea is a valuable source of
1
Department of Agriculture, Cape dietary protein for both humans and their livestock. There is limited information available on cowpea production
Peninsula University of Technology,
Cape Town, South Africa and suitable agronomic practices, such as planting date, to best suit different environmental conditions in South
2
Soil and Water Science, Agricultural
Africa. Therefore, the objective of this study was to evaluate the effect of two locations on cowpea production
Research Council, Stellenbosch, and the effect of planting date as affected by zinc application rate. Field experiments were conducted at two
South Africa locations (Bien Donne’ and Nietvoorbij) in the Western Cape Province of South Africa, using two planting dates
(2 October and 2 November), three cowpea lines (Veg1, M217 and Qukawa) and three zinc (Zn) fertiliser
CORRESPONDENCE TO: application levels (0 kg/ha, 15 kg/ha and 30 kg/ha) during the 2015 growing season. The experimental design
Nonkululeko Mfeka was a randomised complete block with five replicates. The results showed that Veg1 and Qukawa lines
performed significantly better in both vegetative and reproductive parameters when compared to M217 at both
EMAIL: locations. Application of zinc fertiliser significantly (p<0.05) affected seed iron content in Veg1 and M217 at
mfekan@cput.ac.za Bien Donne’ and seed iron content in M217 and zinc content in Veg1 at Nietvoorbij.

DATES: Significance:
Received: 16 Feb. 2018
• Cowpea lines Veg1 and Qukawa were the best performing lines in all parameters measured, making
Revised: 08 June 2018
these two lines suitable for dual purpose cultivation.
Accepted: 23 Aug. 2018
Published: 30 Jan. 2019 • Planting cowpea in November, rather than October, increased the crop production efficiency.
• Cowpea showed a better overall total yield in the sandy soil of Bien Donne’ than in the sandy loam clay
HOW TO CITE:
Mfeka N, Mulidzi RA, Lewu FB.
soil of Nietvoorbij.
Growth and yield parameters of
three cowpea (Vigna unguiculata L.
Walp) lines as affected by planting
Introduction
date and zinc application rate. S Afr Cowpea (Vigna unguiculata L. Walp) is a significant grain and fodder pulse grown around the world.1,2 It serves
J Sci. 2019;115(1/2), Art. #4474, as a dual purpose grain legume crop, providing food for human consumption and fodder for livestock.3 This crop
8 pages. https://doi.org/10.17159/ is successful in most regions because of its ability to survive in low fertile soils4, and withstand alkaline soils5.
sajs.2019/4474 Cowpea is a staple crop in most African countries.6 According to Gomez7, Africa is the leading continent in cowpea
production at 68%, followed by Brazil at 17%, Asia at 3%, the USA at 2%, with the remaining 10% produced by the
ARTICLE INCLUDES: rest of the world. Africa alone accounts for 10 million hectares under cowpea production8 and the crop is indigenous
☒ Peer review to Africa3,9. Cowpea seed as well as the vegetative parts make a major nutritional contribution to the human diet.10
☐ Supplementary material The seed contains 25% protein and 64% carbohydrates11,12, with 27–34% protein in the leaves13,14. In South Africa,
cowpea is mainly cultivated in the Limpopo, Mpumalanga, North-West and KwaZulu-Natal Provinces.15 Cultivation
DATA AVAILABILITY: of cowpea is mainly to maintain the nitrogen status of soil, thereby reducing the costs of commercial nitrogen
☒ Open data set
fertilisers.16 According to Bloem et al.17, biological nitrogen fixation of leguminous crops is an affordable and
☐ All data included
sustainable biological method to enhance soil fertility that is used by South African farmers to increase crop yield.
☐ On request from authors
☐ Not available Cowpea has been identified as a neglected and underutilised crop species, with further research required in some
☐ Not applicable parts of Africa where there is limited information on its cultivation agronomic practices and seed handling as it is
of relatively less commercial interest.18-20 In South Africa, there is very limited information on the cultivation and
EDITOR: agronomy of cowpea because of a lack of interest and funding.21 Recent results have shown that cowpea is still
Teresa Coutinho an underutilised crop.22 According to Quass23, no coordinating body exists for cowpea production in South Africa
and consequently there are no available data on production. This limitation results in poor supply of good quality
KEYWORDS: seed.24 To the best of our knowledge, there is no reported information on the cultivation practices of cowpea in the
vegetative parameters; crop production; Mediterranean climate of the Western Cape Province of South Africa. In this study, we therefore present the first
zinc fertiliser; Western Cape
report on the cultivation of cowpea under two planting dates and at different levels of zinc application in the Cape
Winelands region of the Western Cape Province.
FUNDING:
Cape Peninsula University of The Winelands region contributes to the highest cultivation of grapes which needs high soil fertility. Farmers in
Technology; Agricultural Research the Western Cape Province mostly practice mixed farming which predominantly includes livestock. Integration
Council (South Africa); National of cowpea in the vine-based cropping system of the Western Cape can improve nitrogen and carbon supply to
Research Foundation (South Africa) the soil with a resultant reduction in the use of chemical fertiliser. The dual purpose cowpea tested in the trial will
significantly increase plant-based protein for humans and livestock; and also improve soil fertility for ultimately
improved grape production under limited application of mineral fertiliser.

Material and methods

Cowpea lines and study area
Three cowpea lines were used in the study: Veg1, M217 and Qukawa. These lines were obtained from the
Genebank of the Vegetable and Ornamental Plant Institute of the Agricultural Research Council, Pretoria, South
Africa. Morphological traits of the three lines were recorded according to the International Board for Plant Genetic
© 2019. The Author(s). Published Resources25 as presented in Table 1. The field experiment was conducted at the Agricultural Research Council in
under a Creative Commons Stellenbosch, Western Cape. The experiment was done on two Agricultural Research Council research farms –
Attribution Licence. Bien Donne’ (33°55’S, 18° 52’E, altitude 139 m) and Nietvoorbij (33°65’S, 18°36’E, altitude 149 m) – during the

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 Growth and yield parameters of three cowpea lines
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Table 1: Qualitative and quantitative traits of the three cowpea lines

Trait
Line
GP GH LC FC NMB PPP PA PL PS NPPP PC SPP SC ST SS SW

Veg1 2 3 7 4 4.3 3 3 15.8 3 40.7 1 15.1 3 1 5 11.7

M217 1 2 5 2 4.5 3 5 10.1 5 26.2 2 8.4 1 3 1 14.3

Qukawa 2 5 5 4 4.4 2 3 17.25 3 18.7 3 10.8 2 1 1 14.1

GP, growth pattern: 1, determinate, 2, indeterminate; GH, growth habit: 1, acute erect (branches form acute angle with main stem), 2, erect (branching angle less acute than
above), 3, semi-erect (branches perpendicular to main stem, but do not touch ground), 4, intermediate (most lower branches touch the ground), 5, semi-prostrate (main stem reaches
20 cm or more), 6, prostrate (plants flat on ground),7, climbing; LC, leaf colour: 3, pale green, 5, intermediate green, 7, dark green; FC, flower colour: 1, white, 2, yellow, 3, red, 4, purple;
NMB, number of main branches: average of 10 randomly selected plants; PPP, pods per peduncle, average of mature pods from 10 randomly selected plants: 1=1–2, 2=2–3, 3=3–4;
PA, pod attachment: 3, pendant, 5, 30–90o down from erect, 7, erect; PL, pod length (cm): average of 10 mature pods from 10 randomly selected plants; PS, pod shape: 0, straight,
3, slightly curved, 5, curved, 7, coiled; NPPP, number of pods per plant: average number of pods from 10 selected plants; PC, pod colour: 1, pale tan or straw, 2, dark tan, 3, dark brown;
SPP, seed per pod: average of 10 pods; SC, seed colour: 1, cream, 2, brown, 3, grey; 4, black or dark purple; 5, other; ST, seed texture: 1, smooth, 3, smooth to rough, 5, rough, 7, rough
to wrinkled, 9, wrinkled; SS, seed shape: 1, kidney, 2, ovoid, 3, crowder, 4, globose, 5, rhomboid; SW, seed weight (g): weight of 100 seeds per treatment

2015 summer growing season. The soil at Bien Donne’ has a sandy Table 2: Treatment details and codes
loam texture with a relatively high percentage of sand (77%) and low
clay percentage (14.2%). The soil at Nietvoorbij is a sandy clay loam Cowpea line Name Zinc level Application rate
with 69.7% sand and 20.6% clay. The Western Cape Province has
a Mediterranean climate and the study area has an annual rainfall of
1 Veg1 1 0% Control
278 mm, of which approximately 178 mm falls from March to August.26

Experimental design and treatment 1 Veg1 2 50% Zn

The trial layout was a randomised complete block design replicated five
times with an experimental plot size of 2 m x 1 m. Cowpea seeds were 1 Veg1 3 100% Zn
sown at an inter-row spacing of 0.4 m and intra-row spacing of 0.2 m.
The experiment had four factors: the two planting dates (2 October and 2 M217 1 0% Control
2 November 2015), two soil types (sandy clay loam and sandy loam
soil), three cowpea lines ( Veg1, M217 and Qukawa) and three levels of 2 M217 2 50% Zn
zinc (1= 0% or control, 2 = 50% and 3 = 100%). Soil application of
zinc sulfate (ZnSO4) was done at flowering. The trial consisted of nine 2 M217 3 100% Zn
treatments per location per planting date (Table 2).
3 Qukawa 1 0% Control
Cultivation practices and management
The experimental sites were ploughed, disc-harrowed and levelled into 3 Qukawa 2 50% Zn
experimental plots. Two seeds were sown per stand using the dibbling
method. Plants were later thinned to one plant per stand when the second
3 Qukawa 3 100% Zn
trifoliate leaves had unfolded. Hand weeding of experimental units was
done at 4 weeks after germination and subsequently at 3-week intervals
as needed. Cutworm was controlled by applying Cutworm Bait 4 weeks
after planting, while aphids were controlled with Kemprin 200 EC sprayed Data on vegetative and reproductive parameters as well as the mineral
at a rate of 1.0 mL/L water using a backpack sprayer. content of the seed were subjected to an analysis of variance (ANOVA)
using SAS.28 Treatments were tested at a 5% level of significance and
Data collection and analysis
differences between treatments were separated using least significant
Vegetative data were taken from the inner two rows at 2-week intervals. difference and Duncan’s Multiple Range Test of the SAS 2012 package.
The number of germinated plants was recorded at 7 days after planting
and germination (GP) was calculated as a percentage of germinated Results
plants per experimental unit using the formula of Pahla et al.27:
Vegetative parameters
GP= no. of g/T x 100,
Cowpea lines had a significant difference (p<0.05) in germination
where g is the number of germinated plants and T is the total number of percentage. Line 1 showed significantly more (p<0.05) germination
seeds planted. than Line 2 during the October planting date. Germination percentage
The number of leaves borne on each plant at full leaf maturity was counted was generally higher during the second planting date for both locations
and the number of branches per plant was obtained by counting the main (Table 3). Figure 1 shows germination of the three cowpea lines as
stem of the sample plants. Plant height (m) was measured from the main affected by location.
stem, from ground level to the tip of the plant using a meter ruler. The number of leaves per plant was not significantly different between
Reproductive parameters were collected after harvesting the two middle cowpea lines and Zn levels at the two locations. Line 1 at Zn level 2
rows from each experimental unit. Matured pods from sample plants produced the most branches per plant at Bien Donne’ (Table 4). Lines 1
were counted per plant, weighed (g) and measured in metres. Hundred- and 3 produced taller plants than Line 2 at both locations. The second
seed weight (g) was determined by randomly counting 100 seeds from planting date had a significant effect on all the vegetative parameters
threshed pods per experimental unit using a digital weighing scale. measured at Nietvoorbij.

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 Growth and yield parameters of three cowpea lines
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Table 3: Effect of planting date on the germination rate of three cowpea lines at two locations

Bien Donne’ Nietvoorbij

Cowpea line
October November October November

1 89 a
94 a
81 a
97a
2 75b 93a 53b 93a
3 85ab 93a 79a 95a
LSD0.05 12.25 15.85 15 15.9

LSD0.05, least significant difference; L1, Veg1; L2, M217; L3, Qukawa; T1, 0% Zn; T2, Zn at 50%; T3, Zn at 100%.

Means with different superscript letters within the same column are significantly different (p<0.05).

a b c

d e f

Figure 1: Photograph showing vegetative growth of the three cowpea lines (a,d) Veg1, (b,e) M217 and (c,f) Qukawa at (a–c) Bien Donne’ and (d–f)
Nietvoorbj at 8 weeks after planting for the first planting date.
Figure 1: Photograph showing vegetative growth of the three cowpea lines (a,d) Veg1, (b,e) M217 and (c,f) Qukawa at (a–c) Bien Donne’ and
(d–f) Nietvoorbj at 8 weeks after planting for the first planting date.
Table 4: Effect of cowpea line and zinc application rate on vegetative parameters at two locations
Figure 1: Photograph showing vegetative growth of the three cowpea lines (a,d) Veg1, (b,e) M217 and (c,f) Qukawa at (a–c) Bien Donne’ and
Bien
(d–f) Nietvoorbj at 8 weeks after planting for the first planting Donne’
date. Nietvoorbij
Cowpea line Zinc level Number of 23 Plant height Number of Plant height
Number of leaves Number of leaves
branches (cm) branches (cm)

1 1 65.26a 7.06a 15.52a 59.75a 5.17a 15.60a

23
1 2 67.37a 7.21a 14.05a 63.26a 4.93a 14.60a

1 3 50.06a 6.36ab 12.63a 48.49a 5.06a 14.24a

2 1 47.19a 5.66ab 5.10b 45.39a 3.08a 5.26b

2 2 54.59a 6.20ab 5.14b 58.38a 5.36a 5.49b

2 3 46.91a 4.93b 5.47b 60.50a 4.53a 6.25b

3 1 56.77a 6.90ab 15.17a 56.09a 5.03a 15.75a

3 2 52.18a 6.48ab 12.74a 56.40a 5.30a 14.37a

3 3 52.36a 5.61ab 14.17a 48.32a 3.87a 15.16a

LSD0.05 25.16 2.09 4 25.39 1.64 5.3

Planting date

October 55.13 a
8.17 a
10.09b 27.12b 3.58b 6.82b

November 54.36a 4.52b 12.23a 81.71a 5.94a 17a

LSD0.05 7.27 0.87 1.68 13.37 1.27 2.28

LSD0.05, least significant difference; L1, Veg1; L2, M217; L3, Qukawa; T1, 0% Zn; T2, Zn at 50%; T3, Zn at 100%.

Means with different superscript letters within the same column are significantly different (p<0.05).

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 Growth and yield parameters of three cowpea lines
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Reproductive parameters highest number of seeds per pod; a similar trend was observed in pod
length with Line 2 obtaining significantly fewer seeds per pod and lower
Bien Donne’ pod weight. The second planting produced significantly more seeds per
The effect of cowpea lines on the measured reproductive parameters is pod, and greater pod length and 100-seed weight at this location.
presented in Table 5. A non-significant effect within each cowpea line The three cowpea lines differed significantly in their measured seed
in response to the different Zn levels was observed in most measured mineral contents, except for nitrogen (Table 8). Variation of seed mineral
reproductive parameters. Line 1 at Zn level 1 produced the most pods but content was observed between the different cowpea lines but the non-
these results were not significantly different to the other lines at the same significant response to Zn application was observed for most of the
Zn level. Generally, more pods were produced after the first planting date, minerals measured. However, application of Zn at Level 3 significantly
thereby increasing the pod weight for all treatments at Bien Donne’. increased iron in Line 2 compared to application of Zn at Level 2, with
iron concentrations of 97.75 mg/kg and 83.50 mg/kg, respectively. A
The results of the analysed seed chemical composition of the three
significantly lower Zn content was observed when Zn fertiliser (Level 2)
cowpea lines are presented in Table 6. No differences were found in
was applied to Line 1. The first planting produced significantly higher
the accumulation of potassium among cowpea lines. The three Zn phosphorus and sodium contents.
application levels did not have a significant effect on the seed mineral
content within each line. However, a significant decrease in iron content Seed yield
from 88.75 mg/kg to 77.50 mg/kg was observed with the application of
The average seed yield of the three cowpea lines was 60.7 kg/ha and
Zn in Line 1, representing 12.7% Zn content accumulation. Contradicting
1184.2 kg/ha at Nietvoorbij and Bien Donne’, respectively. The average
results were observed for Line 2 (Table 6). The first planting produced
seed yield per hectare (ha) across the locations is presented in Table 9.
significantly higher seed mineral contents of phosphorus, iron, zinc and
At both locations, Lines 1 and 3 performed significantly better than Line
calcium. 2. At Bien Donne’, Line 3 showed a significant 46.6% yield increase
compared with Line 2. Remarkably, average seed yield at Bien Donne’
Nietvoorbij was about 58% more than that at Nietvoorbij. The results of the current
At Nietvoorbij, Line 1 produced the most harvested pods per plant, and study generally indicate a very poor performance of Line 2 at Nietvoorbij
thereby the highest pod weight (Table 7). Lines 1 and 3 obtained the with up to 87% in seed yield compared with that of Line 1.

Table 5: Influence of zinc application and cowpea line on reproductive parameters at Bien Donne’

Number of pods/ Total harvested Pod weight Number of seeds/ Pod length 100-seed weight
Cowpea line Zinc level
plant pods (g) pod (cm) (g)

1 1 30.02a 1046.1a 2086.3a 16.53ab 16.35b 11.4b

1 2 34.62a 1027.0ab 2221.5a 16.71a 16.42b 11.5b

1 3 31.61a 995.5ab 2019.3a 15.75abc 16.18b 12.2b

2 1 25.99a 831.9abc 1021.9b 9.26d 11.97c 14a

2 2 30.02a 780.9bc 1104.7b 9.65d 11.78c 13.8a

2 3 32.72a 598.0c 973.8b 9.37d 11.52c 13.4a

3 1 19.64a 854.3ab 2157.5a 15.49bc 17.81a 13.7a

3 2 21.61a 869.6ab 2229.7a 14.92c 17.56a 14a

3 3 20.17a 926.6ab 2368.4a 15.54bc 17.57a 13.4a

LSD0.05 15.26 246.59 545.43 51.08 0.57 1.08

Planting date

October 28.86a 936.32a 1926.8a 13.89a 15.28a 12.6b

November 25.82a 835.10b 1673.4b 13.50a 15.27a 13.49a

LSD0.05 4.63 73.82 209.74 0.6 0.33 0.52

LSD0.05, least significant difference; L1, Veg1; L2, M217; L3, Qukawa; T1, 0% Zn; T2, Zn at 50%; T3, Zn at 100%.

Means with different superscript letters within the same column are significantly different (p<0.05).

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Table 6: Cowpea seed mineral content after zinc application at Bien Donne’

% mg/kg
Cowpea line Zinc level
N P K Na Fe Zn Ca Mg

1 1 3.96ab 0.5cd 1.57a 119.25ab 88.75a 35.00b 0.12bc 0.21a

1 2 4.08a 0.49d 1.53a 126.00a 84.25ab 39.00ab 0.11cd –

1 3 3.96 ab
– 1.46 a
128.50 a
77.50 bc
37.25 b
0.10 cd
0.20b

2 1 3.86ab 0.52bcd 1.47a 107.25ab 67.00c 38.25ab 0.15a 0.18c

2 2 3.78b 0.53abc 1.48a 106.25ab 86.50ab 36.25b 0.14ab 0.20b

2 3 3.88ab 0.53ab 1.49a 77.75b 82.25ab 28.75ab 0.15a 0.19bc

3 1 3.94ab 0.54ab 1.52a 111.25ab 79.25ab 39.00ab 0.10d 0.20b

3 2 4.08a 0.56a 1.57a 107.25ab 85.00ab 42.00a 0.11cd 0.20b

3 3 3.98ab 0.53abc 1.53a 80.75b 80.50ab 38.25ab 0.11cd 0.20b

LSD0.05 0.26 0.03 0.13 37.56 10.85 4.12 0.02 0.01

Planting date

October 3.92a 0.53a 1.52a 118.11a 88.06a 39.56a 0.13a 0.19a

November 3.98a 0.51b 1.50a 96.17a 74.39b 36.83b 0.12b 0.19a

LSD0.05 0.15 0.02 0.04 28.19 7.35 2.28 0.01 0.01

LSD0.05, least significant difference; L1, Veg1; L2, M217; L3, Qukawa; T1, 0% Zn; T2, Zn at 50%; T3, Zn at 100%.

Means with different superscript letters within the same column are significantly different (p<0.05).

Table 7: Influence of zinc application and cowpea line on reproductive parameters at Nietvoorbij

Number of pods/ Total harvested Pod weight Number of seeds/ Pod length 100-seed weight
Cowpea line Zinc level
plant pods (g) pod (cm) (g)

1 1 38.31a 542.20ab 1074.2ab 13.78a 16.14a 12.22abcd

1 2 25.47abc 640.57a 1372.5a 13.27a 15.78a 12.11abcd

1 3 33.15ab 647a 1296.7a 13.95a 16.02a 12.5abc

2 1 12.01d 121.50d 121.4c 5.23c 8.24c 9.1d

2 2 17.27cd 121.67d 127.3c 7.87b 11.58b 10.6bdc

2 3 12.29d 180.38cd 180.2c 6.25bc 9.26c 9.4cd

3 1 17.25cd 417.50b 1006.2ab 12.74a 17.23a 14.1a

3 2 21.13bcd 431.80b 1029.5ab 13.65a 17.79a 14.22a

3 3 14.39cd 356.20bc 838.1b 12.24a 16.87a 12.9ab

LSD0.05 12.85 195.61 421.79 1.75 2.07 3.3

Planting date

October 27.61a 405.64a 854.90a 10.56b 13.71b 10.74b

November 15.52b 374.91a 763.16a 11.75a 15.09a 12.98a

LSD0.05 5.55 63.67 179.37 0.83 0.9 1.37

LSD0.05, least significant difference; L1, Veg1; L2, M217; L3, Qukawa; T1, 0% Zn; T2, Zn at 50%; T3, Zn at 100%.

Means with different superscript letters within the same column are significantly different (p<0.05).

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Table 8: Cowpea seed mineral content after zinc application at Nietvoorbij

Cowpea Zinc % mg/kg

line level N P K Na Fe Zn Ca Mg

1 1 3.77 a
0.47 b
1.55 ab
321.5 abc
75.50 c
62.00 a
0.14 c
–
1 2 3.77 a
0.51 ab
1.59 a
356.75 a
75.50 c
57.50 b
– 0.20a
1 3 3.88a 0.49ab 1.59a 346.75ab 73.00c 54.50bc 0.13c 0.20a
2 1 3.81 a
0.51 ab
1.53 abc
277.50 abcd
92.00 ab
50.00 de
0.17 ab
0.18b
2 2 3.86a 0.52a 1.55ab 287.50abc 83.50bc 49.25e 0.19a 0.19b
2 3 3.79 a
0.55 a
1.54 ab
285.25 abc
97.75 a
51.25 cde
0.18 a
0.19b
3 1 3.94a 0.48b 1.45c 210.25cd 77.00c 53.25cd 0.14c 0.19b
3 2 3.97 a
0.49 ab
1.45 c
159.00 d
76.00 c
54.00 bc
0.13 c
0.18b
3 3 3.82a 0.51ab 1.48bc 229.00bcd 77.50c 54.25bc 0.15bc 0.19b
LSD0.05 0.39 0.07 0.09 120.77 13.45 3.76 0.03 0.01
Planting date
October 3.85a 0.52a 1.54a 286.56a 80.67a 53a 0.15a 0.19a
November 3.84a 0.50b 1.51a 263.11b 81.06a 53.53a 0.15a 0.19a
LSD0.05 0.2 0.01 0.05 13.89 7.49 2.8 0.01 0.003

LSD0.05, least significant difference; L1, Veg1; L2, M217; L3, Qukawa; T1, 0% Zn; T2, Zn at 50%; T3, Zn at 100%.

Means with different superscript letters within the same column are significantly different (p<0.05).

Table 9: Average seed yield (kg/ha) across the two locations Discussion
The qualitative and quantitative traits of the cowpea lines studied varied
Bien Donne’ Nietvoorbij (Table 1); the traits outline the morphology of the three cowpea lines
Cowpea Zn
line level studied. Morphological traits of cowpea lines and the importance of these
Yield (kg/ha) Yield (kg/ha) traits are well documented by Egbadzor et al.29 Veg1 and Qukawa had
the highest mean germination rate, while M217 had the lowest number
1 1 1043.15a 537.1ab of germinated plants per experimental unit. The obtained results were
similar to those reported by Wada and Abubakar30 who did a germination
1 2 1110.75a 686.25a test on different cowpea lines and concluded that seed size and viability
of seed are the factors that affect germination on different cowpea lines.
1 3 1009.65a 648.35a The results of the study indicate that Veg1 and Qukawa can successfully
be sown early (2 October) or late (2 November) in the Western Cape
2 1 510.95b 60.7c region (Figure 1). Furthermore, M217 will successfully germinate to
its highest capacity if sown later (2 November) in the growing season
2 2 552.35b 63.65c when temperatures are between 10 °C and 30 °C. Germination rate was
significantly affected by soil type; in sandy loam soil germination was
2 3 486.9b 90.1c more efficient than in sandy clay loam soils as a result of the different soil
textural percentages at the two locations. Similar results were obtained
3 1 1078.75a 503.1ab from a study done by Pahla et al.27 who found a higher percentage of
germination and emergence on sandy loam soils.
3 2 1114.85a 514.75ab
Vegetative parameters of the three cowpea lines differed significantly,
3 3 1184.2a 419.05b which could be associated with genotypic make-up, season or
location.31,32 There were no significant differences in the number of
LSD0.05 272.72 210.90 leaves per plant observed at Bien Donne’ or at Nietvoorbij. Comparable
findings on the number of leaves were documented by Olatunji et al.33
Planting date The two farms had soils of different textures. We have shown that
plants at Nietvoorbij, which has clay loam soils, had the most branches
October 963.4a 427.45a and greatest plant heights compared with those of Bien Donne’. The
results regarding the number of branches are in agreement with those
November 836.7b 381.58a of Shiringani24.
Veg1 and Qukawa showed the greatest plant heights and M217 was
LSD0.05 104.87 89.69
shorter across the two locations. This difference could be associated
with the genetic make-up of each line, as the morphological trait of the
LSD0.05, least significant difference; L1, Veg1; L2, M217; L3, Qukawa; T1, 0% Zn; T2, two lines showed a similar growth pattern. According to Egbadzor et
Zn at 50%; T3, Zn at 100%. al.29, plants that are classified as indeterminate are most vigorous. Veg1
Means with different superscript letters within the same column are significantly had an indeterminate or spreading type plant pattern which concurs with
different (p<0.05). the above statement of Egbadzor et al. According to our results, zinc

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fertiliser application at the onset of flowering did not have a significant 4. Elowad HOA, Hall AE. Influence of early and late nitrogen fertilization on yield
effect on the vegetative growth of cowpea. These findings are contrary to and nitrogen fixation of cowpea under well-watered and dry field conditions. Field
the results of Elowad and Hall4, who concluded that early flowering soil Crop Res. 1987;15:229–244. https://doi.org/10.1016/0378-4290(87)90012-8
application of fertiliser increases the number of branches and pods of 5. West DW, Francois LE. Effects of salinity of germination, growth and yield
cowpea lines. Veg1 and Qukawa were recognised as the best performing of cowpea. Irrigation Sci. 1982;3:169–175. https://doi.org/10.1007/
lines for cultivation at both locations. Parameters such as the number BF00446005
of pods per plant and number of seeds per pod contributed to the total
yield harvested of the two lines. The mean number of pods was in the 6. Ndema NE, Etame J, Taffouo VD, Bilong P. Effects of some physical and
chemical characteristics of soil on productivity and yield of cowpea (Vigna
range of 14–33 per plant. Similar results on 12 genotypes were reported
unguiculata L. Walp.) in coastal region (Cameroon). Afr J Environ Sci Tech.
by Peksen and Peksen34. Generally, Veg1 was the best performing line
2010;4(3):108–118. https://doi.org/10.5897/AJEST09.160
across all cowpea lines and M217 was the worst. Shiringani24 obtained
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per plant in two locations in that study. At Nietvoorbij, Veg1 had the most compendium. Rome: FAO; 2004. Available from: http://www.fao.org/3/a-
pods per plant and no difference was observed between zinc application au994e.pdf
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and the ability to absorb and translocate the nutrients to the sink.35 doi.org/10.4314/ajfand.v11i1.65876
Rathore et al.36 stated that the ability of a plant to absorb available zinc in
9. Khalid II, Elhadallou SB, Elkhalifa EA. Composition and functional properties
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of cowpea (Vigna anguiculata L. Walp) flour and protein isolates. Am J Food
hinder the plant’s ability to absorb and translocate zinc to all parts of the
Technol. 2012;7(3):113–122. https://doi.org/10.3923/ajft.2012.113.122
plants. A fascinating finding from our study was that M217 at Bien Donne’
obtained the highest 100-seed weight (14 g/100 seed). These weights 10. Kebe K, Sembene M. Cowpea (Vigna unguiculata (L.) Walp) field infestation
were significantly higher than those of Veg1 and M217 is regarded as by the bruchids (Coleoptera: Bruchidae) in the northern Senegal: Preliminary
the best performing line. The findings clearly indicate that M217 had the biological and ecological data. J Appl Biosci. 2011;41:2788–2796. http://
bigger seed size, although it lacked in most of the parameters measured. www.m.elewa.org/JABS/2011/41/6.pdf
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Makinde38 concluded that seed size was related to the number of days genotypes [MSc thesis]. Bloemfontein: University of the Free State; 2005.
to flowering and pod formation period. These findings are in agreement
with our observations in the current study, as line M217 was the first line 12. Singh AK, Bhatt BP, Sundaram PK, Kumar S, Bahrati RC, Chandra N, et al.
Study of site specific nutrients management of cowpea seed production and
to flower and bear pods. Zinc fertiliser did not have a significant effect
their effect on soil nutrient status. J Agric Sci. 2012;4(10):191–198. http://
on most of the measured parameters, which could be associated with
dx.doi.org/10.5539/jas.v4n10p19
the time of application and the ability of the plant to absorb the fertiliser.
13. Moswatsi MS, Kutu FR, Mafeo TP. Response of cowpea to variable rates and
Conclusion methods of zinc application under different field conditions. Afr Crop Sci.
2013;11:757–762.
We evaluated the vegetative and reproductive parameters of three cowpea
lines in response to three zinc fertiliser application levels in the Western 14. Belane AK, Dakora FD. Elevated concentrations of dietarily-important trace
Cape Boland region. Our results show that Veg1 and Qukawa performed elements and micronutrients in edible leaves and grain of 27 cowpea (Vigna
better in the measured parameters than M217. Planting cowpea in unguilata L. Walp.) genotypes: Implications of human nutrition and health.
November rather than October significantly increased the crops’ ability to Food Nutr Sci. 2012;3:377–386. http://dx.doi.org/10.4236/fns.2012.33054
germinate efficiently, and thereby increased production efficiency. Bien 15. South African Department of Agriculture, Forestry and Fisheries (DAFF).
Donne was the best location for the production of cowpea as the total Production guidelines for cowpea. c2011 [2015 Feb 13]. Available from:
number of harvested seeds was significantly higher for all cowpea lines http://www.arc.agric.za/arc-gci/Fact%20Sheets%20Library/Cowpea%20
at Bien Donne’ than at Nietvoorbij. %20Production%20guidelines%20for%20cowpea.pdf
16. Frankenberger WT, Abdelmagid HM. Kinetic parameters of nitrogen
Acknowledgements mineralization rates of leguminous crops incorporated into soil. Plant Soil.
The support and technical guidance of Prof. Lewu and Dr Mulidzi are 1985;87(2):257–271. https://doi.org/10.1007/BF02181865
highly appreciated. The study was supported financially by the Cape
Peninsula University of Technology Research Fund, the Agricultural 17. Bloem JF, Trystman G, Smith HJ. Biological nitrogen fixation in resource-
poor agriculture in South Africa. Symbiosis. 2009;48:18–24. https://doi.
Research Council and the National Research Foundation of South Africa.
org/10.1007/BF03179981

Authors’ contributions 18. Chivenge P, Mabhuadhi T, Modi AT, Mafongoya P. The potential role of neglected
N.M., R.A.M. and F.B.L. conceived and planned the experiments. N.M. and underutilised crop species as future crops under water scarce conditions
in sub-Sahara Africa. Int J Environ Res Public Health. 2015;12:5685–5711.
carried out the experiments. F.B.L., N.M. and R.A.M. contributed to the
https://doi.org/10.3390/ijerph120605685
interpretation of the results. N.M. took the lead in writing the manuscript.
All authors provided critical feedback and helped shape the research, 19. Degri MM, Sharah HA, Duada Z. Effects of intercropping pattern and planting
analysis and writing. date on the performance of two cowpea variety in Dalwa, Maiduguri, Nigeria.
Glob J Biosci Biotechnol. 2013;2(4):480–484.
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