Reducing the risk of herbicide runoff in sugarcane farming through controlled traffic and early-banded application

► We measured rainfall-runoff losses of PSII herbicides on sugarcane with trash cover. ► Controlled traffic reduced runoff losses of each herbicide by 47–60%. ► Banded applications reduced herbicide losses by 32–42% compared to broadcast. ► Herbicides on cane trash dissipated with time and were more resistant to runoff. ► Consequently, herbicide losses declined rapidly with time after application. The off-site transport of agricultural chemicals, such as herbicides, into freshwater and marine ecosystems is a world-wide concern. The adoption of farm management practices that minimise herbicide transport in rainfall-runoff is a priority for the Australian sugarcane industry, particularly in the coastal catchments draining into the World Heritage listed Great Barrier Reef (GBR) lagoon. In this study, residual herbicide runoff and infiltration were measured using a rainfall simulator in a replicated trial on a brown Chromosol with 90–100% cane trash blanket cover in the Mackay Whitsunday region, Queensland. Management treatments included conventional 1.5m spaced sugarcane beds with a single row of sugarcane (CONV) and 2m spaced, controlled traffic sugarcane beds with dual sugarcane rows (0.8m apart) (2mCT). The aim was to simulate the first rainfall event after the application of the photosynthesis inhibiting (PSII) herbicides ametryn, atrazine, diuron and hexazinone, by broadcast (100% coverage, on bed and furrow) and banding (50–60% coverage, on bed only) methods. These events included heavy rainfall 1day after herbicide application, considered a worst case scenario, or rainfall 21days after application. The 2mCT rows had significantly (P