"Photographers who explore the world of the potato will find plenty of subject matter," said the FAO's roots and tubers expert NeBambi Lutaladio.
The contest, part of events marking the International Year of the Potato, will help raise "global awareness of the potato's key contribution to agriculture, the economy and world food security," the FAO said.
Photographers are challenged "to capture the spirit of the International Year in images that illustrate potato biodiversity, cultivation, processing, trade, marketing, consumption and utilisation," the statement said.
The potato is the world's number-four food crop after rice, wheat and maize, with annual production of more than 300 million tonnes in more than 100 countries.
Sponsored by Japanese camera maker Nikon, the contest has separate categories for professional and amateur photographers and will award prizes totalling 7,200 euros