Location: Agricultural Systems ResearchTitle: Nitrogen Fertigation Interval for Sugarbeet Grown on Soils With a High Leaching Potential Author
Submitted to: Journal of Sugar Beet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2019
Publication Date: N/A
Interpretive Summary: Applying sufficient nitrogen fertilizer to crops without negatively impacting the environment has long been the goal of agricultural managers. Exceeding the crop’s nitrogen uptake capacity can cause nitrogen pollution to the environment through leaching and gaseous losses to the atmosphere. The efficiency with which plants utilize fertilizer nitrogen can often be improved by matching fertilizer application timing with plant demand leading to both agronomic and environmental benefits. Optimizing nitrogen fertilizer management is particularly important to sugar beet growers because too much nitrogen available late in the growing season reduces crop quality and economic return. ARS researchers in Sidney, MT conducted a field study to determine the best timing for multiple small nitrogen applications to sugar beet grown on soils that have a high risk of nitrogen loss by leaching. They concluded that extending the nitrogen application period past the conventional cutoff date of June 30 does not increase sucrose yield. In fact, applying nitrogen fertilizer as late as August 15 lowers crop quality leading to a reduction in economic return of $146 per hectare.
Technical Abstract: Nitrogen management for sugarbeet is challenging due to variable effects of weather on soil N transformations and N losses and may be particularly difficult on soils subject to N leaching. A field study was conducted to determine if extending the in-season N application termination date beyond the conventional cutoff date of 10 weeks after planting would improve sucrose yield. Three in-season N application timing treatments were evaluated each consisting of three fertigation events totaling 84 kg N ha-1 in addition to a preplant application of 67 kg N ha-1. Treatments were 28 kg N ha-1 applied: (1) every 7-8 days from June 15 to June 30 (10 weeks after planting); (2) every 14-16 days from June 15 to July 15; and (3) every 28 to 32 days from June 15 to August 15. Treatments did not affect yield components, except in 2009 when terminating N application on August 15 reduced root sucrose concentration by 6.0 g kg-1. Compared to the conventional June 30 cutoff, gross economic return was negligible for the July 15 cutoff and was consistently negative (-$145.94 ha-1) for the August 15 cutoff showing no advantage to extending the N application period beyond June 30.