Machine-cane interactions: what is the impact of ‘front-end’ design and harvester operation on product quality and crop ratooning?

Increasing of harvesting speed has been necessary to facilitate the large increases in productivity required by the harvesting fleet to manage sugarcane-industry cost pressures. Whilst the power and processing throughput of the harvesters has been able to easily meet this requirement, the design of the ‘front end’ of the harvesters has undergone relatively little functional change since their initial development over 50 years ago. No attempt has been made to improve the interactions between harvester front-end components and the cane plant with respect to damage caused by the gathering, knockdown or basecutting operations. This is seen as a contributor to poor ratoon performance often seen through the industry. Linking rotational speeds of basecutters and gathering/forward feed components to groundspeed was hypothesised to optimise machine performance and minimise damage over a much wider operating speed range than with current machines. Five harvesters were modified to achieve this outcome. In the subsequent field trials, positive impacts on evenness of machine feed in large crops were noted when operated in the modified configuration High to very high levels of stool damage were typically observed at all settings, however the lower harvesting speed in conjunction with matched component speeds had somewhat lower damage and gave somewhat higher yields in the subsequent crop. To quantify the primary causes of the high levels of stool damage observed, sections in each trial treatment were hand-cut at 20-25 cm height prior to the 2018 harvest, and these sections were then included in the stool damage analysis. Very significant reductions in stool damage were noted in all hand-cut treatments (irrespective of final harvesting- speed parameters), indicating that the gathering/knockdown functions of the harvester are primary contributors to damage. At the subsequent harvest, yield increase of the ‘pre-cut’ sections of the plots at each trial averaged between 8% and 25% higher than the paired full machine-cut sections, with the average yield increase across the 72 plot pairs being 16%. This data indicates that very significant gains can be made by reducing the damage associated with the gathering and knockdown functions of harvesters, and the magnitude of the potential gains warrants significant research focus. Key words Stool damage, crop yield, basecutter speed, gathering spirals, knockdown