DIOSCEREA (YAM) A BASIC STAPLE NIGERIAN ECONOMICAL CROP.

Nigeria is by far the world's largest producer of yams, accounting for over 70–76 percent of the world production. According to the Food and Agricultural Organization report, in 1985, Nigeria produced 18.3 million tonnes of yam from 1.5 million hectares, representing 73.8 percent of total yam production in Africa . [ 1 ] According to 2008 figures, yam production in Nigeria has nearly doubled since 1985, with Nigeria producing 35.017 million metric tonnes with value equivalent of US$5.654 billion. [ 2 ] [ 3 ] In perspective, the world's second and third largest producers of yams, Côte d'Ivoire and Ghana , onlyproduced 6.9 and 4.8 tonnes of yams in 2008 respectively.According to the International Institute of Tropical Agriculture , Nigeria accounted for about 70 percent of the world production amounting to 17 million tonnes from land area 2,837,000 hectares under yam cultivation. [ 4 ] [ 5 ]
Yam, a tropical crop in the genus Dioscorea , has as many as 600 species out of which six are economically important staple species. These are: Dioscorea rotundata (white guinea yam), Dioscorea alata (yellow yam), Dioscorea bulbifera (aerial yam), Dioscorea esculant ( Chinese yam ) and Dioscorea dumetorum (trifoliate yam). Out of these, Dioscorea rotundata (white yam) and Dioscorea alata (water yam) are the most common species in Nigeria. Yams are grown in the coastal region in rain forests , wood savanna and southern savanna habitats. [ 1 ] [ 6 ]
Yam is in the class of roots and tubers that is a staple of the Nigerian and West African diet, which provides some 200 calories of energy per capita daily. In Nigeria, inmany yam-producing areas, it is said that "yam is food and food is yam." However, the production of yam in Nigeria is substantially short and cannot meet the growing demand at its present level of use. It also has an important social status in gatherings and religious functions, which is assessed by the size of yam holdings one possesses. [ 6 ]
Contents [ hide ]
1 Geographic regions
2 Cultivation practices
3 Uses
4 Rituals and festivals
5 Customs
6 References
[ edit ] Geographic regions
The farmland production system in the Ekiti State consists of wetland (20% farms are under this category), upland (50% farms in this category) types and a combination of the two types (30% by the balance farms). A study carried out on the efficiency of the three systems to improve crop outputs to meet growing demands for this food crop, indicates that the "wetland yam based enterprises are the most economically efficient with mean economic efficiency of 0.80 followed by upland yam based enterprises with mean efficiency of 0.79." [ 6 ] The combination of wetland/upland yam based enterprises is assessed as the least economically efficient, with mean efficiency of 0.76. Hence, it has been recommended thatmore yams should be grown more on wetlands. Another recommendation made is to adopt the yam minisett technology developed by the International Institute for Tropical Agriculture (IITA) and the National Root Crops Research Institute (NRCRI). [ 6 ]
Although it is grown widely in Nigeria, the area where it is grown most is the Enugu State (land area of 802,295 km²) one of the five states insoutheastern Nigeria where the labour intensive practices are still the norm and the land holdings are small. They are planted on mounds rather than flat slopes depending on the hydromorphic nature of the soils which are generally of loose soil suitable to grow roots and tuber crops. [ 1 ] While yam production issues have been stressed on agronomical practices, a research study carried out on the economic efficiency ofthis crop grown in this region with small farm holdings, which is labour intensive, reveals that land, labour and material (fertilizers and chemicals), credit and extension servicesinputs have a significant bearing on the yield of yam in the region. [ 1 ]
[ edit ] Cultivation practices
Dioscorea bulbifera
Dioscorea cf. dumetorum
Yam is grown on free draining, sandy and fertile soil, after clearing the first fallow. Land is prepared in the form of mound or ridge or heap of 1 metre (3 ft 3 in) height. The yams recommended for such soil conditions in Nigeria are white yam or white guinea yam (Discorea rotundata) and water yam or yellow yam (Discorea alata) . Planting is done by seed yamor cut setts from ware tubers . One day before planting, the tubers have to be subjected to treatment with wood ash or a fungicide ( thiabendazole ) to prevent damage to the soils. The setts are planted at an interval of 15–20 centimetres (5.9–7.9 in) withthe cut face facing up. Mulching is essential during October–November with dry grass or plant debris weighed down with balls of mud. Dosage of fertilizer application, as essential, is decided after chemical analysis of the soil samples. Manual weeding by hoeing isdone three or four times depending on the rate of weed growth. Two Stakes, each of 2 metres (6 ft 7 in) height are used for staking the plants to vine over it; one for two plants with the other used for bracing with the adjacent stakes. Sorghum stovers are also used for this purpose in the savannah land. Pest and disease control is addressed by cultural control and chemical methods; the pests which affect the plant are nematodes such as root knot Meloidogyne spp. and yam nematode (Scutellonema bradys) , and insects such as yam shoot beetle , yam tuberbeetle and crickets . Weedingof the field is essential and maintaining a 2–3 metres (6 ft 7 in–9 ft 10 in) weed free border around the field is to be ensured. Disease resistant [cultivars] are normally recommended for use. Harvesting is done before the vines become dry and soil becomes dry and hard. Generally, a yield of 10–15 tonnes per ha for white yam and 16–25 tonnesfor water yam are obtained by following prescribed management practices. The harvested yams are stored by tying them with ropes. They have a shelf life of about 5 months. Warehouseswhere they are stored should be made rodent proofwith a metal base and wire netting. Rotten buds and sprouted buds should be removed. (sourced from wiki)