More links and websites
This timeline prepared by the Ministry for Agriculture and Forestry gives a history of the government agencies that deal with agriculture and forestry.
More suggestions and sources
Evans, B. L. A history of agricultural production and marketing in New Zealand. Palmerston North: Keeling and Mundy, 1969.
Nightingale, Tony. White collars and gumboots: a history of the Ministry of Agriculture and Fisheries, 1892–1992. Palmerston North: Dunmore, 1992.
Williams, Maslyn, and Barrie Macdonald. The phosphateers: a history of the British Phosphate Commissioners and the Christmas Island Phosphate Commission. Carlton, Vic.: Melbourne University Press, 1985.