Yield potential of spring-harvested sugar beet (Beta vulgaris) depends on autumn planting time

• Sugar beet is a potential winter crop for industrial sugars.
• Sugar beet yield increased with the length of the season (thermal time).
• September/October planted beets yielded 71–118 t ha−1 in the spring.
• Minimum winter temperatures are potential limitation to production.

Sugar crops grown for biofuel production provide a source of simple sugars that can readily be made into advanced biofuels. In the mild climate of the southeastern USA, sugar beet can be grown as a winter crop, providing growers with an alternative crop that is complementary to existing summer crops. Experiments evaluated autumn planting dates from September to December on the yield of five varieties of sugar beet harvested in the spring. A linear relationship existed between sugar beet canopy width and thermal time. Plant canopy diameter increased <50% between February and May for September-planted beets, while the November-planted beets increased 180–230% during this same interval. The earlier diversion of energies to root production in September-planted beets relative to November-planted beets was reflected in yield. Sugar beet yield increased with increasing thermal time (Tbase = 3 °C) and season length. The earliest planted beets in the autumn had the highest yields, with average yields ranging from 71 to 118 t ha−1 in the spring. The lowest harvested yields (42–69 t ha−1) were produced when beets were planted in late-December 2012 and mid-November 2013. Yields were variable, but equivalent to summer production in Midwest USA. There were no detectable differences in planting dates or among varieties for sugar content in the sugar beets, with Brix averaging 16.1%. One of the potential limitations of autumn-planted sugar beet production in the Southeast USA is the minimum winter temperatures; beets planted in late autumn were stressed with cold temperatures in the early winter. Additional research is needed to evaluate cold tolerance on the various stages of sugar beet growth.