Mrs Sangster and South Waikato dairy farmer Gray Baldwin join incumbent director Rob Hewett on the board.
There were 11 shareholders vying for the three seats - two in the South Island and one in the North Island.
Long-serving directors Joe Ferraby, David Jensen and Peter Wilson step down at the co-operative's annual meeting in Hokitika tomorrow.
A graduate of the Agri-Women's Development Trust's Escalator programme, Mrs Sangster is a director of Alliance Group and chairwoman of the Community Trust of Maniototo.
Farmlands chairman Lachie Johnstone said the shareholder-director election process had shown the pool of rural governance candidates was developing ''real depth'', a matter of special interest to the Farmlands board.
It had been proactive in fostering new leaders in rural governance. It was now into the second cycle of its board observer programme, where an aspiring director had the opportunity to shadow the board for 12 months.
It had also developed To The Core - a three-day governance development programme - with Silver Fern Farms and planning had begun for the second intake.
Farmlands has appointed John Journee as an independent director, replacing Mr Wilson who has retired.
Mr Journee has a 15-year association with The Warehouse Group in both governance and operational roles, including a current role as non-executive director and a previous term as chief executive of Noel Leeming.
Mr Journee is also a past chief executive of Southern Hospitality, past chairman of Powershop, Flux Federation and Max Fashions and a past director of Ezibuy.
