According to the Adinkra Dictionary by W. Bruce Willis, this symbol,
Nyame-Nti or Faith in God, is described as: "This stalk is depicted
as the staff of life in many cultures. It symbolizes to the Akan
(an African tribe) that food is a basis of lifeand that they could
not survive if not for the food that God has placed here on Earth
for their nourishment."

The Asante people of Ghana and the Gyaman people of the Ivory
Coast originally designed the Adinkra symbols. The symbols embody
non-verbal communicative and aesthetic values, as well as the
way of life of the people who designed them. Once used only
by royalty for spiritual rituals, the symbols now are usually
printed on fabric to be worn on celebrative occasions and
during ritual.
References
http://www.welltempered.net/adinkra/htmls/adinkra/nyame-nti.htm
http://africanhistory.about.com/library/bl/blfreestencil-AdinkraNyame-Nti.htm