Genernl Guide for Cowpea Cultivation and Seed Production B.B. Singh, S.R. Singh, L.E.N. Jackai and S.A. Shoyinka
International Insfilute of Tropical AgricuUure PMB 5320, Oyo Road, Ibadan, Nigeria
Genernl Guide for Cowpea Cultivation
and Seed Production B.B. Singh, S.R. Singh, L.E.N. Jackai and S.A. Shoyioka
Ioternational Institute of Tropical 'Agriculture PMB 5320, Oyo Road, Ibadan, Nigeria
Table of Contents Page
Contents Introduction
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Climatic suitability Soil type
II
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II
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1
1 2
Land preparation ..............................................................................................................
2
Fertilization ....................................................................................................................
3
Varietal selection .........................................................................................................
3
Method of planting and spacing ..................................................................................
4
Date of planting
6
Weed control
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II
II
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6
Disease control .........................................................................................................
7
Insect control ............................................................ .................................................. .
7
Methods of spraying
9
~
Harvesti ng .........................................................................................................................
11
Storage................................................................................................................................
11
Special Notes Zero or minimum tillage ............................................................................................... 12 Cowpeas in rice fallow
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II
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12
Cowpeas as intercrop
13
Cowpea seed production techniques •.......•............................•
14
Introduction
Cowpea is the most important grain legume crop throughout the tropical belt covering Asia, the Far East, Africa, Central and Southern America and in the southern US and it provides a major source of protein in human diets. West Africa grows about 75 percent of the world's cowpeas primarily in Nigeria, Niger and Burkina Faso. The International Institute of Tropical Agriculture (IITA) has worldwide responsibility to develop improved cultivars of cowpeas for use by different national programs. in 1971.
IITA initiated systematic cowpea research
Through the concerted efforts of a multidisciplinary team of
scientists, a number of improved varieties have been developed which combine multiple disease and insect resistance with extra-early and medium maturing qualities.
Cultural practices have also been developed to
make cowpea high-yielding and more profitable.
This bulletin provides
information on cowpea culture to serve as a guide to farmers and seed producing agencies. Climatic suitability:
Cowpea is a warm weather crop which grows best in areas where the minimum and maximum temperatures are 20 0 e and 35°C, respectively, during the growing season.
Such temperatures prevail in tropical regions between
12°N to 12°5 throughout the year and therefore, cowpea can be cultivated year round in these areas, if there is enough moisture.
However, in
wet-dry tropical regions, farmers grow the crop in the rainy season. In the regions beyond 12°N and 12°5 the winters become increasingly cold.
In these locations cowpea is grown in the summer season.
But the
2.
longer day-length causes late flowering in photoperiod sensitive varieties and thus, a full 3-month rainy period is needed for a successful crop. During the last 3 years, the rains in the nothern Sudan savanna and sahel ian regions have stopped early causing widespread failure of local varieties of cowpeas which are normally photoperiod-sensitive.
Recent
experiments and field demonstrations have shown that under the same conditions, early and medium-maturing varieties which are photoperiod insensitive do very well and ensure a normal crop. Soil type:
Cowpea can be grown on a wide variety of soils ranging from predominantly sandy to predominantly clay and acidic to basic (pH 4.5 to 8.0).
However,
the best yields are obtained in well drained sandy loam to clay loam soils between pH 6 to 7. Water should never stand in cowpea fields as cowpeas are highly sensitive to water logging.
Even 24 hours of standing
water can adversely affect
c~wpea
to drought stress
~rowth.
Conversely,
than maize and other legumes.
is more tolerant
It is grown in areas
with sandy soils such as the sahel ian regions of West Africa. Land preparation:
A deep plowing with one or two harrows provides sufficient tilth for good cowpea root growth which enables plants to derive moisture from the receding water table in areas of low rainfall.
However. in the forest
zone where soils are fragile and rainfall is heavy, plowing and harrowing cause extensive soil erosion. recommended for such areas.
Therefore. minimum or zero tillage is
3. This method will be described in more detail in the special notes section (page 12). FertiUzatioD:
Cowpea being a legume crop, derives all its nitrogen requirement from the atmosphere. nitrogen.
Root nodules fanned by soil rhizobia fix the atmospheric No artificial inoculation is needed.
The natural rhizobia present
in soil are enough to effect sufficient nodulation.
Experiments have shown
that application of nitrogenase fertilizers reduce nodulation and cause excessive vegetative growth which may adversely affect
seed yield.
Cowpeas like other legume crops, have a large phosphorus and potash requirement.
Phosphorus and pot.assium fertilization is essential in poor soils.
The dose is dependent on the available baseline data.
It has been
Jbserved that the soils in Sudan savanna and Sahel ian regions of Africa 3re very low in phosphorus and potash.
In order to get a good,crop of
:owpea in these regions, fertilization at the rate of 200 kg of 0-15-15 ~er
hectare is needed.
Normally 30-40 kg P20S and 25 to 30 kg K20 per nectare are adequate to ensure good crop growth. Other fertilizers may be used depending upon availability.
These fertilizers should be
incorporated in the soil before planting. Varietal selection:
Choice of a proper variety is the most important factor in crop product路ion. The varieties selected. should combine high yield potential, pest resistance, acceptable seed quality and' desired maturity to suit the prevalent rainfall pattern and cropping systems.
The area extension agent or the nearest
agricultural research station should be consulted before making the final ~hol ce.
4
Three groups of varieties have been developed at IITA.
The most promising
ones are listed in Table 1. Method of planting and spacing: Cowpeas can be planted either on ridges or on flat beds depending upon the field drainage.
Planting can be done manually or by mechanical
planters. Attempt should be made to approximate the following spacing: Medium-maturing varieties:
Early-~aturing
varieties:
Vegetable cowpeas: IT 810-1228-14
IT 820-380-5
75 cm row to row 20 em plant to plant 50 em row to row 10 em plant to plant or 20 em hill to hill with 2 plant per hil'
1 meter row to r~ 25 em plant to p'ant 50 em row to row 15 em plant to plant
Seed required for plalldlll:
Depending upon the seed size and percent germination, about 20-25 kg seeds for medium maturing varieties and 40 to 50 kg seeds for 60-day cowpea varieties are needed to plant one hectare of land. Date of plaad. .:
Cowpeas should be planted when there is sufficient moisture in the soil to pennit germination.
Dry sowing is not advisable.
Also the time of
Tabl e 1.
Promising varieties of cowpea.
Variety
Seed type
Maturity days
Insect resistance
Remarks
A. EarlyJMaturing IT IT IT IT IT IT IT -IT -IT
81 ack smooth Brown smooth White rou9h Bro\lom smooth Red smooth Brown rough Brown smooth White rou9h Brown rough
60-65 65-70 60-65 60-65 55-60 60-65 55-60 55-60 60-65
Red smooth Brown smooth Cream rough Cream rough White rough Red smooth White rough Brown rough
80-85 75-80 75-80 70- 75 80-85 80-85 70-75 70-75
c. Vegetabl e TXEe !T81D-1228-14
White seed
Ready for green pod picking in 55 days. Pods are 30 em long and succulent.
IT820-380-5
Wh i te seed
IT83S-911
White brown
Ready for green pod picking in 45 days, pods are 15-20 em 10n9 and succulent. Ready for green pod picking in 50 days Pods are 30 em long and succulent.
B.
82[-9 82E-1 8 82E -60 82E-789 820-839 84E-124 830-44i 82E-I-1 08 84S-2246-4
Good for areas with short rainy season, catch crop in rice and wheat fallows . Good for fntercropping with maize, mi1let, yam an-d cassava . Aphid resistant Aphid + bruchid + thrips resistant.
Med~~~t urit y_
VITA- 3 VITA-7 TV, 3236 IT 820-716 IT 810-994 IT 810-1064 IT 820-699 IT 810-975
Good for full season cropping specially Thrips resistant in savanna regions Bruchid + thr ~ p resist . and other semi~dry areas. Bruchid resistant BnJchid resistant Thrips resistant
~
6.
planting should be adjusted in such a way that the varieties mature after the end of rainy period.
If cowpeas mature when rains are still on, the
seed quality becomes very poor. unless the farmer has sufficient labor to pick several times and not permit matured pods to remain in the field. Therefore. I1TA recommends that the ideal time to plant medium-maturing varieties is about 65-70 days before end of the rains and extra-early varieties about 45-50 days before end of the rains. Weed control:
Efforts should be made to keep fields weed-free.
The first weeding should
be done at about 3 weeks after planting. the second weeding 3 weeks later. After that, cowpea plants cover the ground and only minor weeding may be necessary. Several pre-emergence herbicides have been identified which effectively control weeds in cowpea fields. "Codal". "Lasso". and "Stomp".
The most corrmon ones are"Galex". "Dual". In case of zero tillage these chemical
are often used in combination with "Paraquat".
Normally. up to 5 litres per
hectare of one of these chemicals is sprayed immediately or within two days after planting (before germination) using about 250-300 litres of water.
Since weed species differ from region to region. the selection of
herbicide should be in consultation with the area extension agent or the nearest agricultural institution.
7. Disease control:
Many of the IITA recommended varieties are resistant to common diseases and, there is no need 路to spray for disease control.
However, IT 82E-60
is susceptible to brown blotch and scab and IT 820-716 and TVx 3236 are susceptible to Septoria leaf spot.
Efforts should be made to control
these diseases in case the incidence is noticed. Treatment of seeds with Benlate (benomyl) at the rate of 4 grams per 1 'kg seed greatly minimizes the incidence of brown blotch. Benlate is not recommended where Phythium stem rot is, a problem.
Subsequent foliar spray applications of the same
fungicide at the rate of 0.6 kg of commercial product per hectare in 400 liters water (25 g/lO liters of water) starting at flowering and 2 weekly intervals will control Septoria leaf spot, brown blotch as well as scab. It is advisable to treat the seeds with a mixture of Benlate (3 g) + Oemosan (3 g) per kg of seeds before planting in fields which have high moisture content such as low lying rice fallows and fields in high rainfall areas.
This fungicide treatment will minimize the losses due
to seedling mortality and root rots. loseet control:
Cowpea is attacked by several insect pests which may reduce yield up to 80 percent. The most damaging field pests include flower thrips, Maruca pod borer and pod sucking bugs.
Efforts are being made to develop
resistant varieties but the available level of resistance against these pests is not high.
Consequently, the crop must be protected by
insecticides, particularly at flowering and pod development stages.
8.
The number and type of
insect~cide
sprays will depend on the nature and
severity of insect infestation and also the cowpea variety.
For example,
if there is an attack of aphids, leafhoppers and beetles in the early stages of growth, followed by severe attack of thrips, the crop must be sprayed beginning 15 _ 20 days after planting (OAP) to 50 OAP in case of 60-day cowpea varieties and from 15 OAP to 70 DAP in case of mediummaturing varieties.
This will require about 4 sprays in case of early-
maturing varieties and up to 5 sprays for the medium-varieties. insect pressure is low, all the 60-day varieties and
thri~s
If the
resistant
medium-maturing varieties such as TVx 3236 and IT 820-716 will require only 2 to 3 well-timed spray applications. The following broad guidelines of insecticidE
sprays on cowpeas
are suggested for farmers: 15-20 days after planting if the crop is infested by aphids, beetles or leafh:Jppers.
s~ray
No.1. ( s per need)' Insecticides:
e.g.
Spray No.2. (Essential) .
30-35 days after planting when flower bud initiation has started. This will control thrips and early attack of Maruca pod borer. Insecticides:
Spray No.3. (Essential) •
Sherpa Plus/Cymbush Super ED/Endosulfan (Thiodan) (not reconlliended for aphids)/ Decis+Dimethoate
e.g.
Sherpa Plus/Cymbush Super ED/Decis+ Dimethoate/Thiodan (not recommended for thrips). 40-45 days after planting when the crop is in full bloom and beginning to pod. This will control thrips and ~~! uca pod borer.
9.
Insecticides: e.g. Spray No.4. (Essential )'
days after planting when the crop is in rapid pod filling stage. This will control Maruca pod borer and pod sucking bugs. 55~60
Insecticides: e.g. Sray No.5. ( s per needr
Thiodan/Sherpa Plus/Cymbush Super ED/ Decis+Dimethoate/Dec1s+Thiodan. days after planting in case of varieties and heavy attack of pod bugs . 65~70
medium~aturing
Insecticides: e.g.
Medlods of
Sherpa Plus/Cymbush Super ED/Decis+Dimethoate Thiodan (not recommended for thrips).
Thiodan/Sherpa Plus/C~bush Super ED/ Decis+Dimethoate/Decis+Thiodan.
1P'1l"''':
There are several methods of applying insecticides. Those commonly used by farmers in the tropics are the following: Knapsack (high volume) sprayer UlV
(Ultra~low~yolume)
ED (Electrodyn)
(CP~3,
Falcon, etc.)
sprayer (with yellow nozzle);
spraye~.
Knapsack Knapsack
spray~rs
require dilution with water. and use emulsifiable
concentrates (Ee) and wettable powder (WP) fonnulations. The amount of water needed to spray one hectare is generally liters.
betw~en
250 and 350
For most of the formulations about 2.5 to 4cc of chemical 1s
mixed with 1 1itre of water just before spraying.
10.
Crop coverage is
gener~lly
quite good by this method because the spray
is directed at the tarqet crop. used in knapsoack sprayer.
Also. several insecticides can be
However, in many areas where water is scarce,
this method of spraying becomes impracticable.
In addition, uneducated
farmers may find this difficult to accurately measure the small quantities of insecticides needed for dilution .• ULV: The Ultra-Low-Volume (UlV) sprayers are very effective in areas where wind speed is not very high.
The sprayer does not require any dilution
and is ideal for use in drier regions.
The sprayer is light and can
be transported across long distances.
Several hectares can be sprayed
in a day.
Normally 4-6 m strips can be sprayed at a time, but the wind
speed and direction have to be right. ULV sprayers require batteries for operation - this is a problem in certain areas.
Despite these shortcomings, spraying with ULV sprayers
have become popular because of wide coveraqe in'a much shorter tim'e than with other methods.
ED: The Electrodyn (ED) system is a more recent innovation which is both easy to use and also less dangerous to the person spraying.
It is
battery operated and the insecticide droplets are electrically charged as they leave the sprayer.
This enables them to be attracted to the
closest plant surface and presence or absence of wind is unimportant. Both ED and ULV spraying techniques are very suitable for use in drier areas where water is scarce. either of these methods.
No mixing with water is required for
11.
At present, only a limited number of insecticides is presently available for use with this method. Harvesting:
Harvesting should be done when pods are dry.
In case of few medium-maturing
'Iarieties, more than one picking may be necessary.
All the 60-day cowpea
varieties and- medium varieties like TVx 3236 and IT 820-716 are nearsynchronous in maturity and therefore, require only one major picking provided they mature at the end of the rainy season.
When weather is
dry during maturity, these varieties drop most of the leaves and picking becomes very easy.
If labor is not available or is expensive, harvesting
can be done by cutting all the plants at the base and leaving them in the field to dry.
Afterwards, these can be manually beaten or mechanically
windrowed and threshed.
Some large farmers have had reasonable success
using a low dosage of paraquat at maturity to force complete drying, followed by combine harvesting. Storage:
Seeds should be properly cleaned and well dried before storing.
Efforts
should be made to dry the grains to about 10 percent or less moisture. Ideally, seeds ShOlfld be stored in airtight containers and periodically fumigated with Phostoxin at the rate of 1 tablet per 100 kg seeds.
This
will protect the cowpea seeds from bruchid damage during storage. Also, treatment of seeds with groundnut oil (and some other oils) at the rate of 5 m1 per kg of seed has been found very effective against bruchids.
However, oil treatment should be used only when storing small
quantities of seeds.
IT 820-716, IT 810-1064 and IT 810-994 are bruchid
resistant varieties and do not suffer much damage in storage.
12.
Special Notes Zero or IDinimum tillage:
Cowpeas can be successfully grown without much tillage by making use of appropriate herbicides .
Zero or minimum tillage may be desirable when
growing cowpeas in rice fallows or in forest zone where rainfall is heavy and causes soil erosion!
The field should be first sprayed with Paraquat
at the rate of 5 litres/ha to kill all the previous vegetation.
About
a week later, the dead weeds should be mowed or slashed and the field planted with cowpeh.
Planting can be done manually or mechanically using rolling
injection planters or tractor drawn cone planters. cide 'is applied within 2 days after planting.
A pre-emergence herbi-
Any of the herbicides
mentioned before can be used in combination with a low dose of paraquat (2-3 litres/ha).
This ensures killing of all weed seeds which germinated
after first paraquat application and checks subsequent germination of weeds.
If properly done, this ensures a clean field for up to 4 weeks
after which a minor weed i ng may be required.
Subseq uent care of cowpeas
is same as described earlier. Cowpeas in rice fallows:
Rice is cultivated throughout the tropics as a rainfed crop.
In most areas
sufficient residual moisture remains in soil after harvesting of rice, particularly in low lying fields to permit the
~rowing
of a successful
crop of '50-day' cowpeas . Our observations indicate that if soil moisture at the time of paddy harvest is enough for normal cowpea germination, then it is enough for the entire cowpea crop.
This is because
13.
cowpea roots grow quite fast and penetrate deep enough to draw required moisture for the plant.
In some situations the paddy fallows may have
excess moisture which may reduce germination.
If there is no standing ,
water in the field. the seeds of some cowpea varieties will germinate rather well.
IT 82E-60 tolerates excess moisture as well as low moisture
and it is one of the best varieties for rice fallows in Africa. number of farmers in Bida. Nigeria. are growing this variety.
A large IT 820-889
appears to be better adapted in Asia. Normally. no cultivation is required before planting cowpea in rice fallows but efforts should be made to spread the trash evenly.
Planting
of cowpeas should be done following the alternate paddy rows so as to maintain a row-row distance of 45 cm but within the rows planting should be done near paddy hills which are normall 20cm apart. be planted per hill.
Two seeds should
A rolling injection planter is ideal for this
purpose. Paraquat (5 litres/ha) should be applied before germinating in order to kill the existing weeds. be weeded before planting.
When Paraquat is not available. the field should The subsequent care of the crop and insect
control measures will be same as described earlier. Cowpeas as intercrop:
Although it is more profitable to grow crop cowpea as a monocrop. the traditional farmer plants cowpea as a mixture with millet. sorghum. yam maize and cassava.
Experiments have shown that, if properly done, the
yields of maize. millet. cassava, yam and sorghum are not reduced in Inixed
14. cropping but an additional 500-1000 kg/ha of cowpeas can be produced from the same piece of land.
This is more so with the '50-day cowpea'
varieties, particularly in those areas where moisture is adequate. Planting of cowpea should be done at the same time as the main crop. Maize, sorghum, millet, yam and cassava should be planted in rows 1m apart inter-planted with 1 row of cowpea. should be 20cm with 1 plant per hill.
The
w~thin-row ~ormal
distance of cowpea
insecticide protection
using the appropriate technique should be given to the cowpea crop. When moisture is not limiting, there will be very little competition for light during the first 40 days. flowered and begun to pod.
By that time cowpea would have
Subsequently, cowpea plants will be a bit
shaded and their yield will be slightly lowered. lower the yield of the cereal or root crops.
The cowpea will not
Thus, a normal crop of
cereals or root crops plus a near nonnal crop of '60-day cowpea' would be obtained from the sante field.
This requires more labor than normal
and is not suitable for large-scale mechanized farming. Cowpea seed production techni,ques:
Availability of pure healthy seed is the first pre-requisite for obtaining high yields.
Cowpea is a self-pollinated crop.
Maintenance of
genetically pure seed is easy provided that due care 路 is taken to rogue off-type plants from the field.
Also, mechanical mixture must be avoided
during threshing. The general production practices are the same as for commercial cowpea production.
The following specific operations must
be done if the crop is being produced for seed purpose:
15.
a)
Begin with pure seed: Obtain pure seed of the variety from the research institution responsible for developing the variety or registered growers of your area.
b)
Maintain isolation from other fields: Plant in a field where other variety of cowpea was not grown the
prev~ous
year.
This field should be at least 5 meters
away from other fields if planted with other varieties of cow;Jeas. c)
Rogue off-type plants: Remove off-type plants from the field at least twice during the growing season.
Off-type plants can be identified by the
different leaf types, different flower color, different pod color, or different maturity period from the variety being multiplied.
A good seed production plot should not have more
than 0.5 percent off-type plants after roguing has been completed. d)
Harvest and thresh carefully: Harvesting should be done in time to avoid field weathering and threshing should be done as not to damage seed or seed coat; this will reduce germination.
e)
Remove off-type seed: The threshed seeds should be examined for anY possible mixture and these should be removed.
Seed mixtures can be ide[1tified if they
have different seed coat color. different hilum color, different
16.
seed size.
For example, IT 82E-60 which has white seeds,
sometimes shows a few black seeds due to outcrossing.
These
seeds should be removed. f)
Clean and dry the seeds well: Seeds should be properly cleaned and very well dried.
Normally
the moisture content should not be more than 10 percent. g)
Store the seeds properly: Seeds should be treated with fungicide + insecticide (Fernason-D at rate of 3 g/kg seeds) and stored in polythene coated Hesian bags on wooden racks in a seed store.
Alternatively, the seeds can
be stored in closed containers or 'in closed rooms by using fumigants such as Phostoxin.