Assessing the sulfur requirements of sugarcane in Queensland

Yield responses in sugarcane to sulfur (S) fertiliser application can be predicted by soil or leaf analyses. In soil, the critical level for S response was determined to be less than 3 mg S/kg. In sugarcane, in the first exposed dewlap leaf sampled at eight months, critical levels of 0.10 mg S/kg DM or total N:S ratio of greater than 17 were determined. These critical levels were established from soil and leaf analyses from replicated S experiments on 16 locations, and from 11 locations where sugarcane responded to S fertiliser application. Critical levels are tentative, as only three of the 35 harvests in the replicated experiments responded to S fertiliser application; consequently most of the evidence is from the 11 unreplicated experiments. Sulfur deficiencies in sugarcane were associated with low applications of S fertiliser and areas that had topsoil removed by either soil erosion or by land levelling. Soil analyses indicate that all regions of Queensland have areas that are S deficient, with Mackay and Burdekin regions having the highest proportion of soils with low S levels.