Corchorus olitorius

General information

Corchorus olitorius is an annual crop. The plant grows well in the lowland tropics, ranging from warm temperate zones through tropical desert to wet forest life zones. It can tolerate an annual precipitation between 400 and 4290 mm (optimum 1000 mm per year^[8]). Some cultivars are sensible to waterlogging, especially when they are young.^[9] Temperatures between 16.8 and 27.5 °C are optimal for the plant growth.^[10][1] For the soil a pH of 4.5 to 8.2 is needed.^[1][10] The plant prefers a fertile, humus-rich, well-drained alluvial soil but also grows well in suboptimal soil conditions.^[11] Before sowing, the soil is prepared carefully by plowing and the seeds are broadcast or dribbled behind the plow in the wet season. The seeds must be pre-soaked 24 hours before seeding for ten seconds in hot water (around 93 °C^[12]) to overcome dormancy.^[13] If the small seeds are mixed with sand, it makes it easier to sow them.^[8] And if the soil is wet, germination takes place two to three days after sowing. In some systems, the seedlings are transplanted at a height of 10 cm.^[8] The plants are grown in rows with a spacing of 20–50 cm. When the plant achieves a height of 8–25 cm, the seedlings are harrowed with a rake three to four times and weeded two to three times.^[9] Cow dung, wood ashes or rotted water hyacinth (Eichhornia crassipes) or its ashes are used as manure.^[9] The yield of the crop responds more to water availability and soil organic matter than to high mineral nutrient status.^[13]

Plant protection

The most serious pests are nematodes from the genus Meloidogyne, leaf-eating beetles and caterpillars. If it is dry, eight to ten weeks after planting, yield losses can occur due to leaf bugs and spider mites attacks resulting in terminal shoot wilt. Damage by nematodes can be minimized by crop rotation. Application of insecticides is also possible, but agent and application time should be chosen carefully since the leaves are harvested for consumption.^[14] Attacks were also observed by weevils species (Myllocerus spp.), semilooper (Anomis sabulifera), and yellow mites (Polyphagotarsonemus latus).^[9] Diseases (bacterial and viruses infections) are not as serious as pests (insect and nematode attacks). Seedling damp-off occurs but can be reduced by good drainage and cultivation in humus-rich soils with adequate water holding capacity. Attacks by Sclerotium rolfsii in dry weather of the late season can lead to wilts at the stem collar.^[14] Anthracnose spots caused by Colletotrichum gloeosporioides may infect the crop but can be easily controlled by spraying copper oxychloride.^[15]

Harvest and yield performance

Harvest can begin after about six weeks:^[8] The whole plant can be directly harvested (for jute production) or leaves are harvested by pruning several times during the vegetation period (for food production). The shoot regeneration highly depends on variety, soil fertility, adequate water supply and control of weeds and pests. Amount of pruned shoots and quality reduces with each harvest. Under farming conditions the yield usually reaches around 2.5 t per hectare of edible leaves. Under experimental conditions and with very high fertility application, yields of about 28 t per hectare have been reported.^[13]

Post harvest and propagation

For fresh consumption the leaves should be stored above 8 °C and below 15 °C. Low temperatures from 1-8 °C lead to browning of the leaves and too high storage temperatures are manifested in leaf yellowing.^[16] To produce seeds, the fruits can be harvested six weeks after flowering. The dried capsules are threshed and can be stored for eight to twelve months in well sealed jars.^[8][13] For storage, the moisture should be around nine percent.^[13]

Future prospects

Corchorus olitorius could be grown in a floating system with nutrient solution and could produce baby leaves, which would be interesting for the fresh cut leafy vegetable industry in Europe.^[17]

Fibre

Most of all the countries India, Bangladesh and other Asian countries make Jute from fibres of the bark tissue of Corchorus capsularis and Corchorus Olitorius, while the fibre of C. Olitorius is of lesser quality. The fibres are extracted from the plant’s bark. They appear golden and silky with a length of up to 3 metres and with a diameter of 2.4 µm.^[18] The plant stalk is cut and then processed by pulling up, rippling, partial retting, breaking, spinning and combing to obtain fine fibres that are well separated from unwanted woody material. Afterwards the fibres are cured and dried.

Manifold textiles are made of jute, e.g. yarn and twine, sacking, carpet backing cloth and other blended textiles. It can as well be a raw material for cords and strings.^[19]

In Africa and the Middle East, a different type is grown with the leaves and shoots being used for food while the fibre is considered of little importance.^[6]

Food

Corchorus olitorius is cultivated in Syria, Lebanon, and Egypt as a potherb^[20] and its culinary use goes back at least as far as the Ancient Egyptians.^[21] It is an important leafy vegetable in Côte d'Ivoire, Benin, Nigeria, Cameroon, Sudan, Uganda, Kenya and Zimbabwe. It is also cultivated and eaten in the Caribbean and Brazil, in the Middle East and in India, Bangladesh, Japan and China. In Nigeria the leaves are boiled to make a sticky, mucilaginous sauce which is served with balls of cassava which are otherwise rather dry.^[6]