In Thailand, horticultural practices are a significant source of non-point source (NPS) pollution, and the government is considering best management practices (BMPs) as control measures for reducing agricultural NPS pollution to water. A prevailing assumption that farmers’ reactions to regulations will be homogenous is not based on underlying insights into attitudinal positions that may explain alternative behavioural responses. This paper uses Q-methodology to identify attitudinal discourses relating to BMP uptake. The approach combines the strengths of qualitative and quantitative research in order to explore subjectivity. The study is conducted with citrus growers in the Ping river basin, where farmers are facing increasing competition from alternative water uses. Four ‘discourses’ or viewpoints are identified, namely conservationist, traditionalist, disinterested and risk-averse. The different attitudes of these four groups are likely to be associated with distinctive behavioural reactions to the adoption of alternative policy instruments for pollution control. These discourses could usefully inform targeted policies for the control of NPS pollution from agriculture.