Sesame (Revised)

Introduction 

Sesame (Sesamum indicum) is a tropical and subtropical plant in the family Pedaliaceae and the genus Sesamum, valued for its edible seeds, oil, and flavor. The genus Sesamum consists of approximately 20 species, with the majority being native to the tropical regions of Africa.
S. indicum is believed to have originated in East Africa, particularly in the region that spans from Ethiopia to Sudan and is the oldest of the commercial oil seeds. Sesame seed is one of the oldest oilseed crops known, domesticated well over 3,000 years ago. The oil is a clear edible oil with a pleasant taste and a very good long shelf life if properly refined. Sesame has an oil content of 48-55% which is the highest of any oil crop while the protein content ranges from 44 to 48%.

It is now cultivated throughout the tropical and subtropical areas in Asia, Africa, and South America. Major sesame-producing countries include India, China, Myanmar, Sudan, Ethiopia, and Nigeria. Sesame is an excellent rotation crop of cotton, maize, groundnut, wheat, and sorghum. It reduces nematode populations that attack cotton and groundnut. It is also an excellent soil builder - as it improves the soil texture and moisture retention and lessens soil erosion. The composted sesame leaves left on the soil binds the ground; retains soil moisture better for planting the next crop; and increases the yield of the following crop. Sesame is resistant to drought, tolerant to insect pests and diseases, a low-cost crop and therefore one of the best alternative specialty crops. 

Sesame seeds are either consumed directly as a highly nutritious foodstuff or processed by the confectionery and bakery industries. The seed hulls, which are bitter due to their oxalic content, can be removed with the use of steam. Ragouts and soups are often prepared with crushed sesame seeds. Sesame hay, if carefully dried, can be used as fodder. A large proportion of the world's sesame production goes towards producing edible oil. Purely white sesame seeds are in demand on conventional and on ecological markets, because of their higher oil content than pigmented varieties. By-products of oil extraction are an excellent protein component to mix into animal feed. 
The seed hulls, which are bitter due to their oxalic content, can be removed with the use of steam. Ragouts and soups are often prepared with crushed sesame seeds. Sesame hay, if carefully dried, can be used as fodder. A large proportion of the world's sesame production goes towards producing edible oil. Purely white sesame seeds are in demand on conventional and on ecological markets, because of their higher oil content than pigmented varieties. By-products of oil extraction are an excellent protein component to mix into animal feed.  (Mkamilo & Bedigian., 2007).

Species account 

Sesamum indicum is an annual, or occasionally perennial herbaceous plant. Stems: erect, branching, reach heights of 1-2 m depending on the variety and growing conditions. It is typically covered in fine hairs. Leaves: simple, alternate, and lanceolate to ovate in shape.. Flowers: solitary, tubular flowers with five petals, vary in color from white to pink. Fruit: a capsule that is typically oblong or rectangular in shape, measuring about 2 to 4 cm in length. When mature, capsule splits open along its seams to release small, oval-shaped seeds. Seeds: small and flat, measuring about 2 to 4 mm in length, vary in color, with common varieties being white, black, brown, or yellow. The seeds are rich in oil and are covered by a thin seed coat.
(Heuzé et al., 2021.

Related species 

Sesamum alatum commonly known as the Winged sesame is found across tropical Africa thriving in arid areas from Senegal to South Africa. It has also been introduced in Madagascar, India, and on occasion, in other regions. 
The plant is an erect annual herb, 50-150 cm. Leaves: heteromorphic: lower leaves 3-5-foliolate or very deeply divided with narrow, linear-lanceolate lobes; upper leaves simple, glabrous, except for some mucilage glands; margin entire. Lower leaves 3-5 segmented and prickly outgrowth present on the leaf Petiole Flowers: 3.5 cm in diameter, pink or light purple outside and red to dark purple in side with reddish-purple spotted within. Fruit: narrow, oblong, long beaked capsule. Seeds: winged at both end, black, rough, 2.5-3mm long.
The leaves and young shoots are gathered from the wild and cooked as a vegetable, often seasoned with crushed seeds. The seeds are sometimes prepared separately as a relish or boiled with pumpkin leaves, served with a staple food. Seeds yield edible oil and are employed as an aphrodisiac and for treating diarrhea and intestinal problems (Jansen, 2004, Hyde et al., 2023).
Sesamum angustifolium (Oliv.) Engl. (Mfuta mwitu (Swahili))
This is a usually erect herb, rarely straggling, sparingly branched, to 1.3 m, occasionally higher. Stems angled, finely hairy. Leaves: Narrow, long. Flowers: Funnel-shaped, pink to reddish purple, hairy, longer lip pale inside with purple lines.
Found from Nigeria east to Sudan and Ethiopia and south to Namibia and Mozambique. It occurs in abandoned cultivated land, grassland, roadsides, 0-3,000 m. Common in light clay and sandy soils. 
It is used as a vegetable by the Luhya, Luo, Teso and Mijikenda of Kenya. The vegetable is has a mucilaginous texture and a slight odour. It is normally cooked with Corchorus, beans and peas and used to thicken sauces. The oil is used to treat ringworm in Uganda (Busoga), while ground leaves combat baldness (Boni). Leaves mixed with water help with eye troubles and infant diarrhea. The mucilage is used for burns and wounds, and crushed leaves add shine to hair during washing. It's also used to relieve stomachaches among the Kamba in Kenya (Maundu et al., 1999.

Sesamum calycinum Welw. 
The native range of the species is Congo to South Tropical Africa. In Kenya it occurs in abandoned cultivated lands, grassland, roadsides, 0-3000m. common in light clay and sandy soils.
The plant is an erect annual or perennial herb, rarely straggling, sparingly branched, grows to a height of 1.3 m, occasionally higher. Stems: angled, finely hairy. Leaves: Narrow, long. Flowers: Funnel-shaped, flower. The leaves and shoots are occasionally collected from the wild and consumed as vegetables. 

Varieties
There are local varieties of sesame with black, white and brown seed colors. The black varieties are grown in the coastal region and the white in the western region of Kenya.
Imported varieties have lower performance than local varieties. The best of the imported varieties is "Morada", identified by its purple stems and leaves. It originated in Congo and further selected in Venezuela. It is higher yielding and more resistant to aphid attack. The local sesame varieties are branched and drought resistant but have a low yielding capacity and are susceptible to most diseases. KS-S6 variety can be grown from 200-1000 masl, gives an average yield of 2.5-3.0 tons/ha. This variety has a high poding ability, is tolerant to rust and shootfly.

Ecological information

 Sesame needs a constant high temperature, the optimum range of growth, blossoms and fruit ripeness is 26 to 30degC.  Sesame only grows well in a warm climate and in East Africa it is only grown from sea level up to 1500 m. Most varieties of sesame are photoperiod sensitive. 

In Kenya sesame is grown in the following areas: 
•    Coast Province - Kwale, Kilifi and Lamu districts
•    Western Province - Busia, Bungoma and Kakamega
•    North Eastern Province - Mandera
•    Eastern Province - Meru
Good harvests can be expected when rainfall of 300-600 mm is equally distributed throughout the vegetation period. Optimum rainfall times: 35% before the first cusps are formed, 45% during the main blossoming period, 20% during the ripening period. Drought during harvesting is preferred. During each of its development stages, the plant is highly susceptible to water-logging, and can therefore only thrive during moderate rainfall, or when irrigation is carefully controlled in drier regions. Due to its tap roots, the plant is highly resistant to drought and can provide good harvests, when soil moisture is adequate.
A wide range of soils are suitable for sesame cultivation. Optimal are well-drained, loose, fertile and sandy alluvial soils that have a pH value between 5.4 and 6.75. When irrigated, or during summer rain spells, sesame grows better in sandy than in heavy soils because it is very sensitive to high soil moisture content. It is not recommended to plant sesame on sloping ground, because its need of weed-free seed beds and its slow rate of early development can lead to erosion. Sesame tolerates temperatures of 24-33degC and the crop matures in 120-140 days.

Agronomic aspects 

Sesame is often sown as an opening crop in a rotation, as it requires a fertile soil. In this case grasses must be eradicated as sesame is a poor competitor to weeds. Planting must be done as early in the rains as possible. A rough seed bed is required despite the small seed size of sesame. A smooth seedbed with a fine tilth is more likely to form a hard cap after heavy rains and prevent germination. 
There are several cultivation methods:
•    Direct sowing in holes, with stick for support.
•    Sowing after narrow strips have been prepared.
•    Drilling in rows about 45 cm apart and later thinned (at a height of about 5-10 cm) to a distance of 15-20 cm within the row.
The optimum depth to sow is around 1.5 to 2.5 cm. It is important to sow at an even depth to ensure simultaneous and uniform growth of the crop. Small-holder farmers will often sow by hand.. This method requires 5-10 kg/ha of seeds. Mixing seed with sand, dry soil, ash or dried, sieved manure or compost will help to make seed distribution more uniform. In order to achieve an optimum crop density, branching varieties should be singled out to 6-10 cm, or definitely less than 15 cm distance within the rows when they reach a height of 5-10 cm.
Intercropping
Sesame is often sown with other crops such as pigeon peas, maize or sorghum. It grows to a height of 1-2 m.
Husbandry
Young sesame plants grow very slowly during the first 25 days, due to the small seed size, and are not yet strong enough to compete against weeds. Natural weed resistance sets in when growth rapidly accelerates, after the plants have attained a height of 10 cm. For this reason, the field should be kept as weed-free as possible during the first 20-25 days after seeding. This is usually achieved through 2-3 hand cultivations or by slashing weeds at soil surface as soon as practically possible, and hand weeding the rows of crops. 
Additional measures in weed control include:
•    Early working in of the weeds and harvest residues from the previous crop.
•    The planting of rapidly-growing varieties.
•    Include plants in the crop rotation that cast strong shadows, or are good ground coverers (e.g. green manure plants).
•    Bottom crops: Ground-covering legumes can be sown between the rows to suppress weed growth (e.g. groundnuts).
 

Harvest, post-harvest practices and markets 

Harvesting