THE USE OF SUGARCANE TOPS FOR LIVESTOCK FEED: A STUDY OF TOPS HARVEST AND CROP IMPACTS

IN A TIME of low sugar prices and consequent reduced farm income, a small group of Burdekin growers formed a consortium to investigate the potential for harvesting cane tops to produce stockfeed, after minimal processing. Their aim was to produce the product for both export and domestic use. Market research indicated that a viable industry of this kind was possible, but little was known of the yields of material available for processing to supply such a market. With the financial assistance of the QDPI Burdekin Rangelands to Reef Initiative and Bureau of Sugar Experiment Stations, this investigation was undertaken to fill the gaps in the knowledge necessary to carry this project to fruition. Two trials were established in erect cane crops scheduled for mid-season and late-season harvest, with removal of tops staggered throughout the drying-off period for the crop. The timing of individual harvest of tops was determined by the last irrigation and the scheduled time for crop harvest. Data collected included fresh weight of tops and biomass of tops per hectare for tops cut both above and below the growing point, cane yields from the remaining crop harvested for normal mill processing, and impacts of the topping procedures on CCS and juice quality parameters. In addition, samples were analysed for organochlorine and organophosphate pesticide residues. Fresh weight and biomass of tops harvested below the growing point generally exceeded those for tops cut above the growing point, with yields for both influenced by the time interval for harvest of tops prior to normal crop harvest. The removal of tops prior to the scheduled crop harvest did not have an adverse impact on final crop yield, but there was a significant reduction in CCS when the tops were removed below the growing point 5 weeks before harvest. A downward, non-significant trend in CCS was apparent in both trials when tops were removed more than 3–4 weeks prior to harvest. The financial returns from tops harvested for stockfeed would necessarily need to be measured against any loss in value of the harvested crop due to any reduction of CCS following early removal of tops. In both trials, the lowest ranked juice purity level was that for tops removal below the growing point for the earliest tops cutting time. This is in line with the decreases in CCS noted for these treatments. There were no other significant adverse impacts on juice-quality parameters associated with early removal of tops. No pesticide residues were found in the tops material, indicating it could be used safely for stockfeed. It was evident from this investigation that harvest of tops for stockfeed production could be carried out successfully without adverse impact on crop production, provided that the tops were harvested within 3–4 weeks of the scheduled crop harvest.