Improving Nitrogen Management in Pacific Northwest Sugarbeet Production.

Nitrogen (N) management is an important factor in sugarbeet production.  Avoiding both under and over supplying N is critical to optimizing yield and quality. Past research has been critical to improving sugarbeet N nutrition.  However, continued research is needed to evaluate recommendations due to evolving varieties and management practices. From 2005 to 2010, studies from 14 locations (14 site-years) were conducted by agronomists from the Amalgamated Sugar Company and scientists at the USDA-ARS Northwest Irrigation and Soils Research Laboratory to evaluate the effect of N supply (fertilizer N + spring soil residual N [NO₃-N + NH₄-N]) on sugarbeet production in Pacific Northwest sugarbeet production area.  At each site-year, the effect of various levels of N supply on estimated recoverable sucrose (ERS) yield, root yield, sucrose concentration, brei nitrate concentration, and nitrogen use efficiency (NUE) were assessed. N supply significantly affected ERS yield for 6 of the 14 site-years. For the 8 N non-responsive sites, the maximum ERS yield was assumed to be the lowest N supply.  The average N requirement at maximum ERS yield across all site-years was 2.25 kg N Mg^-1 beet and ranged from 1.4 to 3.7 kg N Mg^-1 beet. Thirteen of the 14 site-years had an Nr at or below 2.8 kg N Mg^-1 beet, substantially less than current recommendations of 3.5 to 4.0 kg/Mg.  Nitrogen requirements can be reduced in the Pacific Northwest sugarbeet production area compared to past recommendations resulting in significant N fertilizer amount and cost savings.