Improved fertilizer management practice in sugarcane production is a key component in plans to improve Great Barrier Reef (GBR) water quality. Research focused on understanding the wider systemic factors that drive behavioral change in agriculture is currently limited, with the dominant focus on individual farmer and psycho-social factors. Adopting a wider systems perspective, this study examines farming behavior change and the role of supporting services among 238 sugarcane growers (74,597 hectares) in Queensland’s Wet Tropics region who completed surveys reporting on changes in the method they used to calculate fertilizer application rates, along with information on their farm business, socio-demographics, and self-reported importance ratings on a variety of topics. Informed by the Theory of Planned Behavior, survey data are analyzed using regression models to identify factors influencing the change from traditional to improved practice, and early adoption of improved practice. Results indicate growers were less likely to change fertilizer practice if they regarded maintaining good relationships with other local growers as being extremely important, had off-farm income, or had not attended a government-funded fertilizer management workshop in the five years preceding the survey. Similar drivers acted to promote or delay early adoption of improved practice. Results demonstrate the influence of government-funded services to support practice change.