ATTENTION: Do not buy any fields before going for this achievement! If you have bought any field - even from a farmer that has multiple fields - you will void the achievement and need to start over again on a new save!
You only have to do a mission once for each farmer, you can check your 'friendship'-bar if you have done a mission before. But I would suggest to just run down the list below.
Farmer - Field
Richard Write 1, 6
Victor Robinson 2
Peter Wood 3, 4
Simon Colin's 5
George Watson 7
Able Nelson 8
Joshua Allen 9, 13
Gary Turner 10
Dennis Jenkins 11
Erick Roberts 16
Natalie Jonhson 17,21
Maria King 18
Alex Young 19
Daria White 20
James Harris 22, 23, 24
Edward Gomez 25, 27, 28
Robert Cook 26
Steven Bell 29
Mary Evans 30, 31