Spatial variation of sugarcane productivity in the Tully mill district: is it worth worrying about?

There are currently seven sub-districts within the Tully mill area. Block productivity information is currently used to provide area specific recommendations to growers in each of these sub-districts. This is done on the basis that these sub-districts behave differently in response to a range of agronomically important characteristics such as soil type and climate that may warrant different management strategies. The hypothesis that sugarcane productivity varies significantly between sub-districts was tested using 12 years of block productivity data for cane yield and CCS from six sub-districts where long-term data were available. The response of cane yield to month of ratooning, year, sub-district, and all possible interactions was tested, as was the response of CCS to month of harvest, year, sub-district, and all possible interactions using multi-way analysis of variance with the restricted maximum likelihood method (REML) for estimating variance components. The effects of year and of month of ratooning (on cane yield) and month of harvest (on CCS) were similar across the six sub-districts, indicating that the mill district behaved in a uniform manner to yearly trends and seasonal influences. The lack of any major interaction effects between sub-districts suggests that the segregation of block productivity data using the current sub-districts in Tully provides little additional useful information that would help to manage year-to-year or seasonal variability in yield and CSS