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Conclusion

Two different levels of damage during harvesting – mild and normal – were compared at three different sites in three years. The different levels of damage were obtained by using commercially available sugar beet harvesters with different lifting and cleaning techniques, which caused differing degrees of damage. Manually harvested sugar beet were used as the undamaged control. The storage period varied between 61 to 70 days.
Harvesting damage: With low impact harvesting, 78% of the sugar beet had root tip breaks of less than 2 cm, while with the normal system only 16% fell into this category. With normal harvesting 43% of sugar beet had root tips breaks of between 2 and 4 cm, and 32% had breaks of between 4 and 6 cm.
The proportion of perfectly trimmed sugar beet was 32% with low impact harvesting but only 18% with normal harvesting. For both harvesting methods the majority of the sugar beet were inappropriately trimmed: 56% for the low impact method and 71% for normal harvesting.
The proportion of sugar beet without cracks was 92% with low impact harvesting, while the corresponding figure for normal harvesting was 70%.
The area of surface damage to the sugar beet after low impact harvesting was considerably less than after normal harvesting, 1.5 cm2 compared with 6.6 cm2.
Fungus-attacked area at the root tip: At low storage temperature (5 ºC), sugar beet harvested by hand had 1.9% of the root tip attacked by fungi, while the corresponding value for low impact harvesting was 8.9%. However with normal harvesting the average area affected in six trials was 48.6%. At the higher storage temperature studied (15 ºC), the differences were even clearer: sugar beet harvested by hand had 3% of the root tip affected by fungal damage, that harvested by the low impact method 21.1% and that harvested normally 79.6% (average of six trials).
The root tip is a direct point of entry for fungal attack and resulting root rots.
Effect of storage temperature on sugar losses at a given level of damage: For the sugar beet harvested by hand, the sugar losses were less than 0.05% per day at both 5 and 15ºC and thus the higher temperature did not affect the sugar losses. However, increasing the storage temperature from 5 to 15ºC almost doubled the daily sugar losses from low impact harvested and normal harvested sugar beet.
Effect of degree of damage on sugar losses at a given storage temperature: When the three degrees of damage were compared at the same storage temperature, the daily sugar losses increased almost 2-fold between low impact and normal harvested sugar beet at 5ºC and losses increased 2.5-fold at 15ºC. For hard harvested versus normal harvested sugar beet, the increase in losses was around 5-fold at 5ºC and around 10-fold at 15ºC. The actual values are shown in the table below.

Harvesting methods compared Storage temp. (ºC) Sugar losses in storage
(% sugar/day) Difference
Hand harvested v. low impact 5 0.029 0.071 0.042
Low impact v. normal 5 0.071 0.156 0.085
Hand harvested v. low impact 15 0.034 0.136 0.102
Low impact v. normal 15 0.136 0.332 0.196

Hand harvesting 5–15 0.029 0.034 0.0005
Low impact harvesting 5–15 0.071 0.136 0.065
Normal harvesting 5–15 0.156 0.332 0.176

Fungal identity: Studies showed that Botrytis developed from 52% of the damaged root tissue and Penicillium from 50%. Some individual species of Fusarium were found. Damage by the sclerotia-forming fungus Sclerotinia was observed occasionally in the neck.
In summary, this study showed that the degree of damage to sugar beet is critical for sugar losses in storage. There is a positive correlation between increasing degree of damage and increasing sugar losses. The root tip is much more sensitive to damage than other parts of the sugar beet root. The tissue is primarily attacked by fungi such as Botrytis and Penicillium, which are very prevalent in the soil.