The author of a new book documenting traditional methods of growing yam says the book has preserved indigenous crop planting knowledge that's valuable for Pacific farmers.
The book 'Tokanga ko e Mo'ui'anga' has been published in the Tongan language and was launched in Auckland by author Sione Tu'itahi.
Mr Tu'itahi based the book on the experience of the late Kiteau Tatafu, an award-winning farmer in Tonga.
He said Mr Tatafu advanced an historic method which allowed him to harvest several yams from a single root.
"He experimented with how and when to prepare the land and when to grow the yams using the phases of the moon," he said.
"And over that period of 35 years with his systematic experiential approach to his farming, he has developed this time-tested body of knowledge."