MEASURING THE BENEFITS OF THE SRI BASE CUTTER HEIGHT CONTROL SYSTEM AND THE FLOATING BASE CUTTER SYSTEM

THIS paper describes work aimed at reducing the cost of milling (through maintenance, sugar recovery and mill mud) by lowering the amount of dirt in the cane supply. The reduction in dirt in the cane supply was sought by improved harvester operation through base cutter height control systems. The systems were the SRI height control system and the floating base cutters. A test program consisting of six trials was conducted during the 2002 harvest season in order to compare manual base cutter height control, the SRI base cutter height control system, and CNH Austoft’s version of the Copersucar floating base cutters. The test program followed the industry protocol on dirt-in-cane tests, and all tests were conducted under commercial conditions of operation. The blocked tests involved 80–90 t per treatment (manual control, SRI height control, floating base cutters) replicated at least 3 times. Dirt in the cane supply was measured by sampling the cane in the bin and isolating the loose dirt, and by ash analyses of prepared cane samples. Cane loss was determined by collecting all cane remaining in randomly selected 9 m2 quadrats (billets which had fallen off the infield bin were discarded). Any stubble was cut at ground level; the stubble was added to the cane loss. For the conditions under which the trials were conducted, the findings were that the floating base cutters reduced ash-in-cane compared to manual control by 20% when considering both sets of trials. The SRI system lowered ash-in-cane (compared to manual control) by 11%, although this result was not statistically significant (at the 95% confidence level). The floating base cutters increased cane loss compared to manual control by 13% in the Bundaberg trials, and 79% in the Mackay trials, although the latter result was not statistically significant. The changes in cane loss expressed as a percentage are somewhat misleading given that the magnitudes of cane loss increases were relatively small, i.e. 0.14 t/ha (from 1.09 t/ha to 1.23 t/ha) in Bundaberg and 0.40 t/ha (from 0.51 t/ha to 0.91 t/ha) in Mackay. The SRI height control system increased cane loss compared to manual control by 23% (from 0.51 t/ha to 0.63 t/ha); again, this result must be treated with some caution, as the result was not statistically significant.