Response of eight sugarbeet varieties to increasing nitrogen application. I. Root, sucrose, and top yield

Nitrogen management affects both the root and top biomass production of sugarbeet (Beta vulgaris L.). An interaction between genetic factors and the amount of N applied may influence variety selection for different N management and cropping systems practices. A three-year field study was conducted with the objective of comparing the relationship between applied N and root, sucrose and top yield for selected commercial sugarbeet varieties. Eight varieties were treated with five amounts of N (0, 90, 179, 269, and 358 kg N ha-1) at a furrow-irrigated site in northwest Wyoming. Variety affected sucrose concentration and sugar loss to molasses (SLM) in all three years, root yield and sucrose yield in one of three years, and top dry matter (TDM) yield and sucrose:TDM ratio in two of three years. All yield parameters were affected by the amount of N applied (N) in all three years. The variety x N interaction was significant for only the sucrose:TDM ratio in two of three years and was most prominent with 0 or 90 kg ha-1 applied N at which two varieties produced higher amounts of sucrose per unit TDM than the other six varieties. Results do not suggest that N fertilizer management should be variety-specific, but the significant interaction in sucrose:TDM ratio indicates that there may be differences in N response among varieties based on how they partition photosynthate between roots and tops, especially at low levels of available. These differences can help determine which varieties are best suited for different management objectives.