Static Range Nitrogen Management in Northwest U.S. Sugarbeet Production
1USDA-ARS, 2Amalgamated Sugar Company
Nitrogen (N) management is important in sugarbeet production. This paper presents data to support additional research to evaluate a new N management approach in the Northwest U.S. Evaluation of historic data suggest that static N management (fixed range of N supply independent of yields) may have advantages compared to yield goal-based N management in the Northwest U.S.
To evaluate the potential use of static N management, the following information was gathered:
- Average sugarbeet root yields from 1970 to 2016 across the Northwest U.S. were obtained from the USDA-National Agricultural Statistics Service (www.nass.usda.gov).
- Research-based sugarbeet Nr factors were obtained from published recommendations and research data from Amalgamated Sugar Co., University of Idaho, and USDA-ARS (Amalgamated Sugar Company, 1977; Stark et al., 1997; Tarkalson et al., 2016).
To evaluate the relationships between N supply and optimizing sugarbeet root yield in the Northwest U.S., the following analysis was performed:
- The research based Nr factors were multiplied by the average root yields during the time the research was conducted to determine the time-specific optimum N supplies. These time-specific optimum N supplies were compared to scenarios where Nr was not adjusted over time as root yields increased.
Yield Goal Based N Management of Sugarbeet
- The premise of the yield goal based N management is based on a N amount applied per ton of sugarbeet root (Nr = lbs N/ton beet)
- Nr factors were determined based on research studies conducted periodically. New Nr values were published in 1977, 1997, and 2011.
- New research data was summarized in 2021 from studies in 2018 and 2019. This data will be presented later.
Graphical Comparison of Root Yield, Nr, and N Supply Needed To Maximize Sucrose Yield Over Time
--Average annual root yields in the Amalgamated Sugar Co. growing area (Idaho, Oregon, Washington) (red circles)
--Publihed Nr factors (blue circles): A = 1977 published Nr - University of Idaho and Amalgamated Sugar Co.; B = 1997 published Nr - University of Idaho; C = 2011 published Nr - Algamated Sugar Co. and USDA-ARS; D = 2021 determined Nr - Algamated Sugar Co. and USDA-ARS.
--N supply (soil available N top 3ft in spring + fertilizer N) needed to maximize sucrose yield (black squares). Calculated as: Research Nr * Root Yield.
- The average N supplies needed to maximize sucrose yield were within a range of 13 lbs N/acre. This indicates that as yields increase the needed N supply is similar from 1977 to 2021.
- Greater N supplies are not needed as yields increase.
Recommended N Supplies Over Time Using Latest Nr Factor
- Graph shows the recommended N supplies using the most current published Nr factors.
- Recommended N supplies increase over time with a given Nr factor because yields are increasing every year.
- New research (new Nr) recalibrated the actual needed supplies.
- The fast-increasing yields over time leads to excessive recommended N.
- To use a yield goal-based approach over time, continued research each year will be needed to adjust the Nr factor. This would be impractical based on research-based constraints.
- 20 site years representing all research sites that make up published recommendations in 2011 (2005-2010) and 2021 (2018-2019).
- The bars represent the amount of excess N fertilizer was applied using a Nr based approach compared to what was needed to maximize yield.
- All but 2 sites had excess N supplied.