Objectives (1) To apply novel population health theory to the modelling of injury experiences in one particular research context. (2) To enhance understanding of the conditions and practices that lead to farm injury.

Design Prospective, cohort study conducted over 2 years (2007–09).

Setting 50 rural municipalities in the Province of Saskatchewan, Canada.

Subjects 5038 participants from 2169 Saskatchewan farms, contributing 10 092 person-years of follow-up.

Main measures Individual exposure: self-reported times involved in farm work. Contextual factors: scaled measures describe socioeconomic, physical, and cultural farm environments. Outcome: time to first self-reported farm injury.

Results 450 farm injuries were reported for 370 individuals on 338 farms over 2 years of follow-up. Times involved in farm work were strongly and consistently related to time to first injury event, with strong monotonic increases in risk observed between none, part-time, and full-time work hour categories. Relationships between farm work hours and time to first injury were not modified by the contextual factors. Respondents reporting high versus low levels of physical farm hazards at baseline experienced increased risks for farm injury on follow-up (HR 1.54; 95% CI 1.16 to 1.47).

Conclusions Based on study findings, firm conclusions cannot be drawn about the application of population health theory to the study of farm injury aetiology. Injury prevention efforts should continue to focus on: (1) sound occupational health and safety practices associated with long work hours; (2) physical risks and hazards on farms.