ASSBT Biennial Meeting – Feb. 24 – Feb 27, 2025 in Long Beach, CA
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Static Nitrogen: Evaluating an alternative method for determining nitrogen requirement in sugarbeet.


The current method for determining nitrogen (N) requirement in sugarbeet, the Yield-Based Approach, calculates N fertilizer requirement by applying a ‘lb N per ton beets’ multiplier to the projected yield for a given field. As yields continue to increase over time, this method results in higher and higher N recommendations and a constant demand for research-based updating of the N multiplier. Despite the trend for increasing yields, research has shown the amount of N required to achieve those yields has remained relatively stable. For this reason, researchers from Amalgamated Sugar’s SBQI team, in partnership with soil scientists at the USDA-ARS, have been exploring possible alternatives to the yield-based approach. From 2014 to 2018 a study of 14 fertility field trials concluded that nitrogen requirement could be reduced in the Pacific Northwest and that a flat-rate, or static, approach should be considered as an alternative to the yield-based approach (Tarkalson et. al, 2014). Further work in 2018-19 at 6 field sites identified a static-N range of 180–230 lb N/acre was optimal to maximize sugarbeet yield and quality. This report details the findings of static N research at a further 6 field sites in 2020 and 2021. These studies compared the Yield-Based approach to a range of Static N alternatives (180, 205, 230 lb N/A), as well as N recommendations from a commercial soil testing laboratory. Results showed the Static rate approach better matched N supply with crop need, and that both the Yield-Based Approach and Soil Lab recommendations significantly over-estimated N fertilizer requirement. The current Yield-Based method resulted in an average of 81 lb N/acre excess fertilizer N when compared to the Static N approach.