EFFICACY OF PRE-EMERGENT HERBICIDES ON FRESH TRASH BLANKETS—RESULTS ON EARLY-HARVESTED RATOONS

WEED MANAGEMENT is an important issue affecting productivity and profitability in sugarcane production in Australia. The recent development of an integrated weed management program by BSES Limited has highlighted a range of on-farm activities that can contribute to the effective control of weeds. In particular, it has been identified that weed management in green-cane trash blanketed (GCTB) sugarcane-production systems is an important component of this overall strategy. This paper reports experiments conducted in 2009–2010 on early-harvested ratoons. In two trials, the preemergent herbicides that were tested were equally efficient in controlling total weed populations either when trash was present or on bare soil. On GCTB, negligible effects on yields were obtained when weeds were controlled with pre-emergent herbicides compared to the untreated control (no statistical difference). Previous trials done in lateharvested ratoons led to similar outcomes. A third experiment assessed if incorporating the pre-emergent herbicides just after application or one month after application had an effect on their efficacy. Incorporation by irrigation one month after application appeared to achieve better control of the weed population (mainly grasses in this trial) than an immediate incorporation after spraying. Pre-emergent herbicides that have this ability to remain stable until activated with the first rainfalls when the weed pressure increases are flexible weed management tools for growers.