Yam is a common food in Africa,Asia and South America.it is a common name for some specie of crop of the Genus Dioscrorea and belong to the family of Dioscoreaceae.They are perennial plants.They are monocotyledon(that is a plant with one embryonic seed leaf).They are rich in carbohydrate.
Some varieties of sweet potatoes are called yams as they flowering plants.However it does not belong to the family of Dioscoreaceae but belong to the family called Convoivulaceae.
There are different cultivars of yams which are popular in Nigeria.They include
- White yam - Diocorea Rotundata
- Water yam - Diocerea Glata
- Aerial yam - Diocerea Buldbifera
4.yellow yam -Diocorea Cayenesis - Bitter Yam - Diocorea Dumentorium
THE CLIMATE REQUIREMENT
For yam ,it require the temperature of 25 degree C-30 degree C.The rainfall is between 100cm to 180 cm per annum,abundant sunshine and a well drained sandy -loamy soil which is rich in humus.
PLANTING DATES:
There are two planting season for yam in Nigeria.The early yam is planted between November and December while the Late yam is planted between March and April.
PLANTING PROCEDURE:
The farmland is prepared by clearing the farmland.Heaps,ridges and mound are made.This can be done either manually with the use of hoe or through ploughing ,harrowing and ridging mechanically .
An opening is done on the heap or mound and a whole seed tubers(that is Yam sett)or a tuber portion (that is yam mini sett) are planted inside the mound or heap.The determining factors for a great crop yield are :
- How and where the setts are planted
- The sizes of the mound or heaps
- The yam species
- The inter-plant spacing
- The tuber size desired at harvest.
Preferably ,the yam is inserted with the cut surface turned upward and slantly placed a an angle of 45 before covering it with soil.The cut yam sett should be dried and dusted with chemical such as Aldrin dust before planting in order to prevent rotting and pest attack of the sett.
SPACING:
The spacing for yam sett is 90cm by 100cm while yam mini sett is 25cm by 100cm.
SPROUTING:
The sprouting occurs between 4 to 7 weeks after planting.
CULTURAL PRACTICES:
The heaps or mound should be covered with dry leaves to reduce soil temperature ,conserve soil moisture and prevent rotting .proper and regular weeding should be done to control pest and reduce weed competing with the crop for nutrient.Apply 200kg -250kg of N.K.P fertilizer .The yam should be staked with strong stick or bamboo
HARVESTING:
Yams are typically harvested in Nigeria by hand using sticks,spades or digger.Yam harvesting is tedious,labor intensive and physically demanding.Caution need be take so as not to damage the tubers when harvesting.