Yam is one of the most important food crops in Nigeria, and New Yam Festival is celebrated every year by almost all ethnic groups in the country. Depending on the location, it usually holds every year towards the end of June or early August to October. It is considered a taboo to eat newly harvested yam before this date.

The New Yam festival celebrations are most pronounced in the middle belt, south-west, and south-east of the country. Like other festivals, New Yam is a way to showcase Nigeria’s rich cultural heritage and the traditions of various ethnic groups in Nigeria. The festival features music and dancing, fashion displays and food. It also gives tourists or visitors an opportunity to join and have a feel of Nigerian culture.
Among the Igede people of Benue State (middle belt of Nigeria), the New Yam festival is called Igede Agba and is celebrated in September every year.

In Igbo land (south-east Nigeria), depending on location/dialect, it is called Orureshi, Iwa ji, Onwa Asaa, Iri ji, Ike ji, or Otute.

In Yoruba land (south-west Nigeria), it is called Odun-Ijesu. Odun-Isu or Eje.

The essence of the New Yam Festival is to offer thanksgiving to the Almighty God who gives increase, and also to celebrate our very rich cultural heritage.
SOURCES
http://www.guardian.ng
http://www.vanguardngr.com
http://www.tribuneonlineng.com
http://www.pulse.ng