Effect of Harvest Date and Storage Period on Root Yield and Quality of Two Sugar Beet (Beta vulgaris L.) Varieties

Rim Mansour
Ghab Research Center, General Commission for Scientific Agricultural Research (GCSAR)
Faculty of Agriculture, Damascus University,
2010

Abstract

Applying the recommended agricultural practices on sugar beet can give higher root production and sucrose content, affecting the extractable sugar. However, delay transport of fresh roots to the factory will cause a big loss in sugar content of roots. Therefore, it will be necessary to deliver the harvested sugar beet roots directly for manufacturing and not leave them in the field under the environmental circumstances such as high temperature at harvest time, and thus to avoid the qualitative and quantitative deterioration of sugar beet root because the sucrose changes into reducing sugar (glucose and fructose) by respiration of roots and invertase activity, and it will be difficult to extract sugar from the roots. Therefore an increase in sucrose content could be achieved, and in some cases the product will be only molasses. On the other hand, storage method of sugar beet could mitigate the deterioration in quality and root weight.
This study was conducted at Ghab Research Centre for two seasons 2008 and 2009 to study the effect of harvest date and length of storage period on root yield and quality of two sugar beet varieties (Beta vulgaris L.). Planting date was in winter. Two varieties were used: monogerem (Scorpion) and multigerm (Sultan). The roots were harvested at three harvest intervals (180, 210, 240 days post-planting) to determine the effect of harvest date on root yield and quality. The harvested roots were stored by three storage methods (uncovered, covered with shoots, shaded area) to determine the effect of storage method and number of days ( from harvesting to manufacturing of sugar beet roots) on qualitative deterioration of and root weight. Split-plot design with four replications was used.
The results showed that harvest date at interval 210 days post-planting resulted in high percentage of sucrose content (%), purity (%), shoots per plant (g) in both years, extractable sugar per unit area in second season 2009, while delay harvest time to 240 days after planting increased percent brix (%) and reduced sugar (%), root length (cm) and its diameter (cm), root yield. Moreover, storing roots in shaded area might mitigate deterioration of sucrose content in both years, purity percent, root weight (g) and brix (%) in the first year 2008. While storing roots by covering with vegetative shoots reduced percent brix and percent purity and root weight. It has been found that keeping roots for 24 hours after harvest increased brix on average 11.34% , 3.88% and 4.16% in reduced sugar at 24.17 , 5.94 and 15.45% for the three harvest dates respectively. Sucrose and purity percent were decreased on  average 3.02 and 13.67% at first harvest date, 0.65% and 5.26 at second harvest date, and 2.45% and 6.53 at third harvest date respectively, along with root weight at average 9.17% at first harvest date, 5.93% at second harvest date,2.63% at third harvest date.
Key words:
sugar beet, harvest date, storage method, varieties, yield, quality,  traits, postharvest.