Herbs, shrubs, trees, twiners and climbers. Roots of many species, particularly those in Papilionaceae, possess tubercles. Leaves are alternate, pinnately compound, and rarely simple, as observed in rattlewort (Crotalaria sericea), camel’s foot tree (Bauhinia), and some species of Desmodium (e.g., D. gangeticum).
These leaves have a swollen base known as the pulvinus; stipules are two in number and usually free. Flowers are bisexual and complete, exhibiting either regular or zygomorphic symmetry, and are hypogynous or slightly perigynous.
Calyx sepals usually five, with the odd one anterior (away from the axis), occasionally four, united or free. Corolla petals typically five, with the odd one posterior (towards the axis), sometimes four, free or united.
Androecium stamens usually 10 or numerous, occasionally reduced to fewer than 10, either free or united. Gynoecium carpel single; ovary one-celled, containing one to many ovules, superior in position with marginal placentation.
The ovary is often borne on a stalk, termed a stipe or gynophore. Fruit is commonly a legume or pod (dehiscent) and sometimes a lomentum (indehiscent).
This is the second largest family among dicotyledons, second only to Compositae. It displays a wide range of characteristics and has therefore been divided into three sub-families: Papilionaceae, Caesalpinieae, and Mimoseae.
These divisions are based primarily on floral and stamen features. All three sub-families are well represented in India. From an economic point of view, this family plays a significant role.
Note: The order Rosales, according to Bentham and Hooker as well as Engler, includes both Rosaceae and Leguminosae.
However, Hutchinson raised Leguminosae to the rank of an order with three families Caesalpiniaceae, Mimosaceae, and Papilionaceae. It should also be noted that Leguminosae is the largest plant family in India.
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Agronomic Importance and Production of Cowpea (Grain Legume)
1. Botanical Identity and Local Significance
Cowpea (Vigna sinensis or Vigna unguiculata (Walp.)), commonly known as bean, is indigenous to West Africa. It holds nutritional and agronomic significance due to its high protein content and versatility in food preparation.
Cowpea is consumed alone or in combination with maize, rice, or fish. Bean flour is also processed into fried or boiled cakes. Additionally, cowpea serves as a cover crop, contributing to soil fertility through nitrogen fixation.
It supports sustainable farming systems and plays a crucial role in crop rotation. In Nigeria, major producing states include Borno, Zamfara, and Kaduna.
2. Soil, Climate, and Variety Adaptation
Cowpea thrives best on fertile, loamy soils and requires rainfall ranging from 760 to 1,520 mm during the growing period. It performs well in the dry regions of northern West Africa. Varieties differ in seed colour white, black, brown, or mottled—and in growth habit dwarf, prostrate, creeping, or climbing.
Recommended varieties in Nigeria include Mala, Nigeria-67, Ayi, Kwarra, Alabama Black-eye, Prima, Farin Juda C, Kudi, and Dinner (FARV-13). Ghana recommends the Black-eyed cream-seeded variety.
A newly developed variety, Ife Brown, was released by the Institute of Agricultural Research and Training (IAR&T), Obafemi Awolowo University, Ile-Ife.
It flowers within 35 days of planting, is erect, day-neutral, and preferred due to its brown, wrinkled seed coat. The Dinner variety is used mainly as a green vegetable, with pods harvested 8–10 days after flowering.
Recommended Cultivation Practices for Cowpea
Seeds are sown as a sole crop from July to August in northern regions and in September in southern regions. Interplanting with yams, maize, or sorghum is also practised.
Three seeds are sown per hole at a depth of 4 cm. For row planting, rows are spaced 75–90 cm apart, with plants 25–30 cm apart within rows.
In Kabba Province, two cropping seasons allow the first sowing between March and April.
Germination occurs 4–5 days after sowing, and maturity is reached in 2–4 months. Two rounds of weeding are typically carried out before the canopy closes.
Manual weeding is often preferred to avoid damaging vines, although herbicides like Pendimethalin (40–50 ml/4 L water) can be used. Traditional varieties exhibit extended flowering periods, offering yield security despite pest attacks.
Pods are harvested when they turn yellow but before shattering, usually from December to January in southern areas, and from November to December in the north.
Harvesting is mostly manual. Threshing involves beating dried pods in sacks with sticks, followed by winnowing. Mechanised farms use cutters and threshers or combines.
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Cowpea Yield Performance and Post-Harvest Handling
Yields are low due to pest pressure. Sole crops produce 700–1,000 kg/ha, while intercrops yield 168–448 kg/ha. Proper insecticide application, such as Cypermethrin during flowering and podding stages, can boost yields to 1,680–2,240 kg/ha.
For storage, seeds should be fumigated using Phostoxin tablets or a 3:1 mixture of Ethylene dichloride and Carbon tetrachloride. Storage containers must be airtight and pest-free.
Common Pests of Cowpea and Control Measures
Cowpeas are susceptible to several insect pests throughout growth and storage stages:
1. Pre-flowering pests: Ootheca mutabilis and Alcidodes leucogrammus
2. Post-flowering pests: Maruca testulalis and Piezotrachelus varium
3. Harvest and storage pests: Callosobruchus maculatus
Cypermethrin at 20 ml/10 litres of water is effective in managing these pests.
Beetle Infestation and Its Impact on Cowpea Production
Many beetles, or bean weevils, feed on cowpea leaves and pods, reducing growth and yield. Infestation affects both field crops and stored seeds. A single weevil larva may cause a 5% weight loss in infested seeds.
Nigeria experienced a loss of 24,000 tonnes of beans to weevils in 1968. Field control is difficult, but storage damage is preventable through treatments such as Phostoxin dusting.
Classification of Beetle Attacks:
1. Pre-flowering beetles: Ootheca mutabilis and Alcidodes leucogrammus
Ootheca mutabilis feeds on leaves, reduces yield, and spreads cowpea yellow mosaic virus. Alcidodes leucogrammus causes stem girdling and boring, leading to stunted growth.
2. Flowering-stage beetles: Maruca testulalis and Teniothrips spp.
Maruca testulalis larvae bore into flowers, causing flower drop and later feed on developing pods and seeds.
3. Post-flowering beetles: e.g., Coreid bugs such as Anoplonemis curvipes
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