Sugar beet response to varied plant populations—Current and historic trial results

Abstract Since the end of the 1980s, plant populations (PP) of 80,000–100,000 plants ha −1 have been considered optimal for sugar beet ( Beta vulgaris L.) cultivation without singling in temperate climate. Since then, however, yield levels and growing conditions have changed. To determine the current PP optimum, three field trials with PP from 55,000 to 130,000 plants ha −1 were carried out in Germany in 2022 and 2023, measuring canopy ground cover (CGC) via RGB images as well as sugar yield and taproot quality. Additionally, a meta‐analysis was carried out including literature data from the past 60 years (18 studies, 111 trials) to record possible changes in the optimum PP over the past decades. In the field trials, the sugar yield increased by 8% when the PP was increased from 55,000 to 100,000 plants ha −1 , while the CGC of 85%, indicating complete light interception, was advanced by 160°C day thermal time (base 3°C). In response to the PP variation, thermal time to reach 85% CGC highly correlated with sugar yield. Individual plants had no physiological source limitation, as they could more efficiently build up sugar yield with a higher taproot‐to‐leaf ratio, partially compensating for the yield loss due to the reduced plant number at lower PPs. PPs above 100,000 plant ha −1 produced only little additional yield. The meta‐analysis revealed no change in the optimal PP over the past decades. Thus, the PP of 80,000–100,000 plants ha −1 is still valid for current sugar beet cultivation with sowing to a stand in temperate climate.