Effect of atmospheric carbon-dioxide enrichment on development and yield of sugar beet (Beta vulgaris L.)

Context Rising atmospheric carbon-dioxide (CO 2 ) concentrations are expected to influence sugar beet development, yield, and quality, yet most existing evidence are from greenhouse experiments with limited validation under field conditions. Methods This study evaluated the effects of elevated CO 2 (eCO 2 , 600 ppm) on sugar beet development, yield, and quality under free-air carbon-dioxide enrichment (FACE) conditions. Field experiments were conducted in 2023 and 2024 using two modern sugar beet varieties grown under ambient CO 2 and eCO 2 . Leaf area index (LAI), taproot diameter, leaf and taproot biomass, white sugar yield, and taproot quality parameters were assessed, including an intermediate harvest. Results Under eCO 2 , LAI and taproot diameter were generally higher across both varieties and years. Taproot biomass was consistently higher under eCO 2 at both intermediate and final harvests. The white sugar yield was 1.2–1.3 times higher than ambient CO 2 across both varieties and years. The taproot-to-leaf ratio of both varieties generally increased under eCO 2 . Sugar content under eCO 2 showed a slight increase in 2023 and a slight decrease in 2024 across both varieties, with no consistent response of other taproot quality parameters across years. Conclusions The results demonstrated that under field conditions, the primary effect of eCO 2 on sugar beet is enhanced taproot biomass rather than consistent changes in sugar content. This field-based evidence highlighted that future increases in atmospheric CO 2 could increase white sugar yield primarily through higher taproot biomass production, providing valuable insights for breeding strategies aimed at optimizing biomass allocation.