Environmental stimuli promoting sucker initiation in sugarcane

The presence of suckers, late-formed tillers, in mature sugarcane crops reduces the sugar concentration of harvested material to the detriment of profitability. The amount of suckering varies with cultivar and season. However, the environmental stimuli promoting suckering, i.e. the number of suckers, are not understood. This paper describes the effects on suckering of increasing soil moisture, nitrogen, and the level of light penetrating the canopy. Light was manipulated by plant spacing or removal of dead leaf from mature stalks. Increased nitrogen availability late in the crop's growth cycle promoted suckering, even in a cultivar of low suckering propensity. Higher levels of nitrogen applied at the beginning of the growing season had inconsistent effects, possibly due to variation in rainfall. Increased soil moisture late in the growing season greatly increased suckering and also had a positive effect when combined with high levels of nitrogen. The effect of plant spacing on sucker number was only significant in the plant crop, and then only when expressed as sucker number per mature stalk. Removal of dead leaves had a significant effect on suckering at one site but not another. In all cases, higher plant spacing and dead leaf removal increased light levels recorded under the canopy. The quality and quantity of light required to promote suckering still remain unknown, as does the means by which the plant perceives the light stimuli. The differences in suckering between the plant and ratoon crops suggested that not all stimuli were tested in the treatments applied, or that other factors negated stimuli that were present or that suckering is inherently more prevalent in ratoon crops. All cultivars tested responded similarly to the environmental stimuli that produced a significant effect.