The Timing of Sugar Beet Harvesting Significantly Influences Roots Yield and Quality Characteristics

The accumulation of sugar beet (<i>Beta vulgaris</i> L.) root yield across Central and Eastern Europe typically occurs mostly from July to September but can vary substantially depending on precipitation patterns. When summer rainfall is insufficient, the period of intensive yield accumulation may be delayed, often affecting the technological quality of the roots. Conversely, as light and thermal conditions deteriorate in autumn, growth processes slow down, and each cultivar’s response to late-season conditions may vary. To investigate these dynamics, we examined nine sugar beet cultivars (Zeltic, Pacific, Mariza, Everest, BTS 2205N, Jaromir, Jantar, Eliska KWS, and Klara) under three harvest dates (8–10 September—first date; 7–8 October—second date; and 3–5 November—third date) during the 2020–2021 growing seasons. Both cultivar and harvest timing had a significant impact on root yield, sucrose content, and the concentrations of molasses-forming elements (K, Na, and α-amino N), though the magnitude of these effects strongly depended on weather conditions. In 2020, which was characterized by very high precipitation in June and August, harvesting in early September resulted in optimal yield for most cultivars, with no significant benefit from delaying harvest. However, in 2021, when precipitation was moderate and more evenly distributed, later harvest dates enhanced both yield and sucrose content in several cultivars (e.g., Eliska KWS and Jantar). Among all cultivars tested, Eliska KWS consistently demonstrated high root yield and sucrose content. The sucrose content in the roots was strongly influenced by weather conditions in each study year. In 2021, which had average water availability, sucrose content was high, and delaying the harvest led to an increase in sucrose content while reducing molasses-forming elements in the roots. In contrast, in 2020, during summer rainfall, the effect of harvest date on quality traits was significantly weaker and largely dependent on the cultivar. These findings underscore that choosing the optimal harvest date is highly site- and season-dependent, shaped by precipitation distribution, late-season temperatures, and cultivar genotype. In practical terms, these results can help producers and sugar processors align harvest schedules with local conditions to optimize both root yield and technological quality.