The 2009 ASHS Annual Conference

The adoption of mechanical harvesting systems for processing oranges is a major goal of the Florida citrus industry. However, a number of issues have limited the extensive adoption of this new technology, among them being the amount of leaves and stems, or dead branches (collectively termed ‘debris’) which the shaking mechanism that effectively harvests mature citrus fruit can also remove during harvest. This debris makes its way into loads of fruit delivered to the processor, thereby increasing transportation and processing costs. The objectives of this research were to determine the amount and types of debris in mechanically harvested loads of sweet oranges and to determine if the use of the abscission compound 5-chloro-3-methyl-4-nitro-pyrazole (CMNP) could reduce the amount of debris. Mechanical harvesting was found to increase the amount of debris per load of fruit by as much as four times compared with hand harvested fruit. This translates into approximately 81.5 kg of debris per 27 t load compared with 30.5 kg for mechanically harvested and hand harvested fruit, respectively. Across harvesting method, leaves were the largest component of debris, accounting for approximately 60% of total debris, small stems (< 5 mm diameter) accounted for approximately 38% and the remaining 2% was large stems (> 5 mm diameter). In addition, the amount of soil particulate matter (sand) on the surface of mechanically harvested fruit was found to be approximately three times greater compared with hand harvested controls. The use of the abscission compound CMNP allows for less aggressive shaker operation to achieve the same level of fruit removal by selectively loosening mature fruit. We found that the reduction in shaker frequency associated with CMNP use reduced the amount of total debris per load to levels similar to hand harvested controls. The use of CMNP had a greater effect on the amount of leaf debris per load, such that leaf and small stem debris each accounted for 50% of the total debris; large stems were completely eliminated with the use of CMNP. The data from this study can be used in the refinement of debris elimination systems for mechanical harvesters to eliminate debris before the fruit are delivered to the processing plant and in economic analyses to determine the costs/benefits of mechanical harvesting.