Yield potential of spring-harvested sugar beet depends on autumn planting time

Authors: Webster, Theodore; GREY, T - University Of Georgia; Scully, Brian; Johnson, Wiley - Carroll; Davis, Richard; BRENNEMAN, T - University Of Georgia

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2015
Publication Date: 1/4/2016
Citation: Webster, T.M., Grey, T.L., Scully, B.T., Johnson, W.C., Davis, R.F., Brenneman, T.B. 2016. Yield potential of spring-harvested sugar beet depends on autumn planting time. Industrial Crops and Products. 83:55-60.

Interpretive Summary: The US passed the Energy Independence and Security Act in 2007, which required utilization of 136 billion L of liquid renewable fuels by 2022. In an effort to restrict the amount of corn diverted from food production to meet this goal, sugar-based crops have been investigated as an alternative biofuel feedstock. Bioethanol from sugar beet has a comparable, or superior rating for greenhouse gas emissions, relative to both corn and sugarcane. While not traditionally grown in the southeastern coastal plain, sugar beet has potential as a biofuel feedstock and alternative winter crop for growers in the Southern USA. Sugar beet is very adaptable to various edaphic conditions, tolerating soils with pH greater than 6.5 and various textures and organic matter contents, and can be grown on marginal land. Sugar beet has many benefits over competing biofuel crops, including: 1) lack of conversion of harvested material into sugars; 2) an established industry in other regions; 3) existing varieties, germplasm, and breeding programs; 4) effective and registered tools to ensure crop protection; 4) alternative potential end-use products beyond only biofuels (e.g. dairy feedstock, bioplastics, pharmaceuticals, and any other industrial sugar needs); 5) lack of physiological maturity, so crop can be harvested over a range of time based on demand. Field studies found positive linear relationships between sugar beet yield thermal time (Tb=3°C), with yields increasing with season length. The earliest planted beets in the autumn had the highest yields, with average yields for each year ranging 69 to 118 Mg/ha in the spring. The lowest harvested yields (42 to 69 Mg/ha) were produced when beets were planted in late-December 2012 and mid-November 2013. Yields were variable, but equivalent to summer production in Midwest US. 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.

Technical Abstract: 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. Experiments evaluated autumn planting dates from September to December on the yield of five varieties of sugar beet that were mechanically 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 to 230% during this same interval. The earlier diversion of energies to root production in September-planted beets relative to November-planted beets was seen in yield. There were positive linear relationships between sugar beet yield thermal time (Tb=3°C), with yields increasing with season length. The earliest planted beets in the autumn had the highest yields, with average yields for each year ranging 69 to 118 Mg/ha in the spring. The lowest harvested yields (42 to 69 Mg/ha) were produced when beets were planted in late-December 2012 and mid-November 2013. Yields were variable, but equivalent to summer production in Midwest US. 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.