Earlier studies have shown that the biological oxygen demand (BOD5) of water that has been in contact with sugar juice, sugarcane trash and in runoff water from sugar-cane fields can be very high. The development of management strategies that minimise the impact of runoff water from sugarcane fields requires an understanding of the rate of breakdown of sugar and trash, and how this may be changed by environmental factors (such as water content) and degree of contact with the soil. This study presents further data on the BOD5 of the runoff water following harvest for two cane growing areas, Burdekin (3 sites) and Pimpama (1 site). The data show that, following harvest, the BOD5 in the water can be substantial even 51 days after harvesting. Studies were undertaken in the laboratory with soil from one site in the Burdekin (Rita Island) to investigate the effect of trash incorporation and soil water contents on soil respiration and the rate of disappearance of water-soluble carbohydrates in the soil. Both measurements we found to follow a first order kinetic reaction. It is suggested that incorporating the trash into the soil and keeping the soil moist when irrigation is available should achieve a reduction in BOD5 in runoff water. Harvesting areas near environmentally sensitive waterways for 3?4 weeks prior to the start of the wet season should be avoided or undertaken with due care.