Pigeon pea (Revised)

Pigeon pea (Cajanus cajan) commonly known as pigeon pea is a perennial legume plant that belongs to the Fabaceae family and the Cajanus genus. The genus Cajanus encompasses a total of 34 species. Within Africa, two indigenous Cajanus species are recognized: Cajanus kerstingii Harms, found in West Africa, and Cajanus scarabaeoides (L.) Thouars, which is distributed along the coastlines of Africa and Madagascar, as well as in certain inland areas. Pigeon pea is an important grain legume crop of rain-fed agriculture in the semi-arid tropics.

Main pigeon pea producing regions are the Indian sub-continent, Central America and Southern and Eastern Africa. Pigeon pea is produced as a vegetable or export grain crop in southern and eastern Africa. In Kenya, pigeon pea is the third most widely grown pulse crop, and it is one of the fastest growing cash crops with an annual growth rate of 3% in the last decade. Green pigeon pea is being exported from Kenya to Europe (Snapp et al, 2003). The dry grain is also an important local pulse and export commodity in several African countries (Kenya, Malawi, Mozambique, Tanzania and Uganda) (Minja, et al, 1999). 

Pigeon pea is a perennial shrub that is commonly grown as an annual crop. It has very slow initial development (up to 2 months after planting). With a deep taproot, pigeon peas are able to take up nutrients and water from lower subsoil layers. Therefore, in crop mixes they hardly compete with the companion crops. This crop grows and yields well under conditions of low rainfall and poor soil.  Pigeon pea is well balanced nutritionally and an excellent source of protein. It is eaten as a vegetable (immature pods or green pea) or as dried grain (cooked and eaten as dhal, dry split cotyledons). The crop has many other uses: the wood is used as fuel, and the leaves and husks provide livestock feed. 

Pigeon pea is useful as tall hedges on dry soil and on the bunds of paddy fields. The branches and stems can be used for baskets and firewood. It is often grown as a shade crop, cover crop or windbreak. After establishment, pigeon pea improves the soil by its extensive root system. The bacterium Rhizobium that lives on the roots of the pigeon pea is able to fix nitrogen and thus to improve soil fertility. Fallen leaves are used as mulch. Traditional uses as medicine are many, e.g. young leaves are applied to sores, herpes and itches. 

India is one of the largest producers and consumers of pigeon pea. Other significant producers include Myanmar, Kenya, Malawi, and Tanzania. The demand for pigeon pea is driven by its nutritional value and versatility in cooking. In Africa, pigeon pea is an important crop, especially in regions with challenging environmental conditions such as drought and poor soil. It contributes to food security and provides an additional income source for many small-scale farmers. Countries in East and Southern Africa, such as Kenya, Tanzania, Malawi, and Uganda, are among the key producers of pigeon pea on the continent.
(Van der Maesen, L.J.G., 2006, Orwa C. et al., 2009, Plantvillage (n.d)) 

Species account

Cajans cajan is a short-lived perennial (1-5 years) shrub, usually grown as an annual. Depending on the variety and growing conditions, it can reach heights ranging from 1 to 4 m. Leaves: are trifoliate, composed of three leaflets that exhibit an ovate or lanceolate shape. These leaflets possess a smooth margin and a prominent midrib. Flowers: vibrant yellow hue, although there are cultivars that exhibit white or reddish petals, grouped in clusters at the terminal ends of branches. Each flower is endowed with five petals, with the uppermost petal often displaying slight variations in both size and color. Fruit: elongated straight or sickle-shaped pod, ranging in length from 3-10 cm, 4–9-seeded. Splits into 2 spiraling valves. Seeds: oval-shaped and come in a variety of colors, including green, yellow, brown, or speckled. 
(Orwa C. et al., 2009, Van der Maesen, L.J.G., 2006, Hyde, M.A et al.,2023).

Variation in Pigeon
Pigeon pea, exhibits significant variation in its characteristics such as growth habits (erect, semi-erect, or sprawling), leaf forms, flower colors (white, cream, yellow, red, and purple), and seed shape (round to oval) color (light beige to dark brown) and sizes. 
This variation has been influenced by geographical distribution and local preferences. Deliberate breeding has further contributed to this diversity, leading to the development of cultivars tailored to specific climates and soils. Notably, some cultivars have been bred to mature in fewer months, catering to the needs of different regions. It’s important that farmers consult with local extension officers for suitable cultivars.

Pigeon pea varieties in Kenya and their characteristics:

Examples of pigeon pea varieties in Tanzania

• "Komboa" (performs well below altitude of 1500 m; early maturing about 90 - 100 days; grain mottled cream and brown; potential yield of about 4 t/ha)
• "Mali" (adapted to altitude between 500 - 1500 m; medium maturity: 130 - 150 days; grain yield 1.0 - 3.0 t/ha; resistant to Fusarium wilt; tolerant to insect pests and drought)
• "Tumia" (performs well below 1500 m altitude; recommended for areas with low to medium rainfall (250 - 600 mm); maturity less than 150 days; grain yield of 1.8 - 2.4 t/ha; white grain colour; susceptible to Fusarium wilt; tolerant to drought)
• "Luwe 1 - 5" (maturity of about 159 days; grain yield of 1.2 t/ha; white grain colour; susceptible to Fusarium wilt)
• "KAT 60/8" (as in Kenya)

Examples of pigeon pea varieties in Uganda

• "KAT 60/8" (as in Kenya)
• "Apio Elina" (local variety; grown between 1000 - 1175 m; maturity: 6 - 9 months; grain yield: 250 - 500 kg/ha)
• "Adyang" (local variety; maturity: 6 - 9 months; yield: 250 - 450 kg/ha)
• "ICPL 87091" (maturity: 97 - 104 days; gain yield: 1.99 t/ha; white grain colour)
• "ICPL 87101" (maturity: 93 - 102 days; grain yield: 2.2 t/ha; brown grain colour)
• "ICPL 90029" (maturity: 92 - 104 days; grain yield: 1.6 - 2.5 t/ha; brown grain colour)

Propagation is by seed, stem cuttings rarely succeed. Pigeon pea varieties differ not only in form of seeds, colour and taste, but also in growth habit, time of flowering and susceptibility towards pests and diseases. Seed rate: 20-25 kg per ha (8-10 kg per acre).

Ecological conditions

Optimum temperatures for pigeon pea cultivation range from 18 to 38°C. Pigeon pea does not tolerate frost. Above 29°C, soil moisture and fertility need to be adequate. Rainfall optimum is 600-1000 mm/year. Pigeon pea is a short day plant. Flowering is triggered by short days, whilst with long days plants grow vegetative. It is sensitive to high salinity and to water logging. It flowers well where rainfall is 1500 to 2000 mm. On deep, well-structured soil it will grow where rainfall is 250 to 370 mm. Pigeon pea is rarely found above altitudes of 2000 m. Drained soils of reasonable water-holding capacity and with pH 5-7 are favourable for its growth. Pigeon pea does not tolerate shallow soils or water logging. 

Agronomic aspects

In intercropping, the crop performs well with 2 rows of cereals (e.g. sorghum, millets), cotton or groundnut. After harvest of the intercrop, long-duration pigeon pea continues to grow and protects the soil. Pigeon pea is regarded as a good plant for restoration of fertility and is used in a rotation with crops such as maize-groundnut-tobacco-pigeon pea for three to four years in Uganda. One of the advantages of pigeon pea is the increased growth of the grass interplanted with it. In Uganda, it is usually sown in alternate rows with sesame or African finger millet (Eleusine coracana), and in Malawi with maize. In Tanzania, the main intercrop is cassava. In Kenya, sorghum and maize are the most common intercrops with pigeon pea. However, due to its high demand, there is a tendency to move away from traditional intercropping to monocropping. In Ukambani and Coastal strip, Kenya, the crop is grown commercially in large plots. 
 

Harvest, post-harvest practices and markets

Harvest
The crop is usually cut near the ground when most pods are mature, or mature pods are picked individually. Green pods are picked over a long period in home gardens or hedge crops. Ratoon cropping is mostly practiced in pigeon pea producing areas in Kenya. After harvest the stems are cut back to facilitate re-growth and a second crop is harvested in the subsequent season.

Post-harvest practices
Entire air-dried plants or pods are threshed, usually by hand or with cattle, and seed is cleaned. Clean bins prevent insect attack, which can be considerable. Storage as split peas reduces bruchid attacks. Processing includes dhal making, either wet (after sprinkling heaps of seed) or dry, by milling.

Markets
Main pigeon pea producing regions are the Indian sub-continent, Central America and Southern and Eastern Africa. Pigeon pea is produced as a vegetable or export grain crop in southern and eastern Africa. In Kenya, pigeon pea is the third most widely grown pulse crop, and it is one of the fastest growing cash crops with an annual growth rate of 3% in the last decade. Green pigeon pea is being exported from Kenya to Europe (Snapp et al., 2003). The dry grain is also an important local pulse and export commodity in several African countries (Kenya, Malawi, Mozambique, Tanzania and Uganda) (Minja, et al., 1999).

Nutritional value and recipes

Pigeon pea is a nutritious legume that offers a range of health benefits. Pigeon peas are a good source of plant-based protein, making them a valuable component of vegetarian and vegan diets. They provide a substantial amount of amino acids, the building blocks of protein, aiding in muscle growth and repair.
Furthermore, pigeon peas are a good source of dietary fiber, which supports digestive health by promoting regular bowel movements and preventing constipation. The fiber content also helps regulate blood sugar levels, contributing to better glycemic control. This can be particularly beneficial for individuals with diabetes.
Additionally, pigeon peas contain a notable amount of vitamins and minerals. They are a good source of B-vitamins such as folate (vitamin B9), which is crucial for DNA synthesis and cell division, making it especially important for pregnant women. The legume also provides minerals like iron, potassium, and magnesium. Iron is essential for oxygen transport in the body, while potassium and magnesium play roles in maintaining proper heart function and nerve signaling. Pigeon peas are low in saturated fat and cholesterol, making them heart-healthy. Incorporating them into the diet can contribute to reducing the risk of cardiovascular diseases. (van der Maesen, L.J.G., 2006.
Further reading: 
•    https://www.1mg.com/articles/pigeon-pea-arhar-6-amazing-health-benefits-it-offers/
•    https://www.boldsky.com/health/nutrition/2018/health-benefits-of-pigeon-peas-126903.html

Table 1: Proximate composition of 100g edible portion.

Source (Nutrient data): FAO/Government of Kenya. 2018. Kenya Food Composition Tables. Nairobi, 254 pp. http://www.fao.org/3/I9120EN/i9120en.pdf

RE=retinol equivalents.

RAE =Retinol activity equivalents. A RAE is defined as 1μg all-trans-retinol, 12μg beta-carotene, or 24μg α-carotene or β-cryptoxanthin.

^$ Draining the water several times leaches away water soluble nutrients significantly.

^a Lewis, J. 2019. Codex nutrient reference values. Rome. FAO and WHO

^b NHS (refers to saturated fat)

^c https://www.hsph.harvard.edu/nutritionsource/water/

^d British Heart Foundation

^e FDA

^f NIH

^g Mayo Clinic

Nutritive Value per 100 g of edible Portion

*Percent Daily Values (DV) are based on a 2000 calorie diet. Your daily values may be higher or lower, depending on your calorie needs. 

Recipes

1. Kitalolo (Green banana with vegetables) (Tanzania)
Ingredients
    30 green banana (Mlali)
    1 kg mbaazi (pigeon peas)
    Handful cowpea leaves
    1 tbs soda
    2 lts sour milk
Procedure
    Boil small beans with water until half cooked in a clay pot 
    Peel banana, cut into cubes, add into the clay pot
    Sort, cut into small pieces the cowpea leaves and add into the mixture with soda and water, keep boiling until soft. 
    Remove the pot from heat and mash thoroughly 
    Add sour milk, stir until soft and liquid like porridge, serve.
Variations
    Add butter or animal fat
    Use pigeon pea instead of small beans
    If served and remain left over for the nest day, add milk and stir well. 
    Serve.
    Consumed by women and children only and not men
    For sick people
Nutritive value 
    Carbohydrates
    Protein
    Minerals – sodium, calcium e.t.c 
    Vitamins – A, B - Complex e.t.c.
    Water

2. Makukuru/Ngararimo (mashed maize with peas)

Ingredients
    4 kg maize
    2 kg beans (nganana/ pigeon pea)
    2tbs soda
    Water
Procedure
    Boil the maize with soda and water in a clay pot until soft
    Add beans into the pot to boil until done
    Remove the pot, mash to make semi hard. Serve
Variation
    Add salt to the taste
    Add cooking oil or fat to add palatability 
Serve 
    Serve without mashing
    Serve with stew or sour milk 
    Serve as main dish
    Serve as a packing lunch
Nutritive value 
    Carbohydrates
    Protein
    Minerals e.g. Sodium
    Vitamins e.g. B-Complex

3. Ngunza kutu ((Kamba, Kitui, Kenya)
Ingredients
Pigeon peas (dry)
Pearl millet or maize flour
Method
    Boil nzuu (pigeon peas) till well cooked
    Fry the nzuu
    Add water to boil 
    Add maize flour or mwee flour and cook to ugali
    Serve alone
    Eaten by all