Sugar Beet Soil Science

Nitrogen management in sugar beet production can be a bit touchy compared to other crops. Sugar beet root yields are maximized with vigorous growth early- and mid-growing season. Adequate nitrogen availability early in the growing season promotes this growth. Sugar beet root quality, however, is promoted when the crop begins to run out of nitrogen late in the growing season.

Essentially, too little nitrogen early in the growing season decreases root yield, while too much nitrogen late in the growing season decreases root quality. Root quality is defined by the sugar and impurity concentrations of the harvest root. Sugar beet processors frequently pay premium dollar for higher quality sugar beets, making it well worth a producer's time to pay special attention to nitrogen management practices. Much research has been devoted to nitrogen management in sugar beet production and will continue as new and different nitrogen management practices are created and tested.

Nitrogen Source and Timing Trials

We just completed field trials to examine nitrogen sources and application timing of nitrogen fertilizer on sugar beet production. These trials were conducted in an area where previous data and producer experiences strongly suggested a good sugar beet crop required substantially more nitrogen than other areas of the Red River Valley. The original hypothesis proposed that additional nitrogen fertilizer was required because N was probably lost through denitrification when soils were excessively wet. Previous research supported this hypothesis. Two three-year trials examined:

  • spring vs. fall pre-plant fertilizer application;
  • banding near the seed row vs. uniform broadcast;
  • urea vs. a poly coated slow release nitrogen source; and
  • all the above mentioned factors combined with applying some nitrogen fertilizer as a sidedress at the 10- to 12-leaf growth stage.

Results

  • Unlike previous research, the sugar beets required more normal or lower nitrogen rates to achieve maximum root yield in these three research years. As a result, there was no difference between fall and spring applied nitrogen.
  • Polycoated urea was not different than urea when applied in the fall but decreased yields and increased quality when applied in the spring.
  • Sidedressing nitrogen had little effect on yield.
  • Banding nitrogen was not always different than uniform broadcast, but when there was a difference, higher yields were obtained with the uniform broadcast.

Further data analysis and interpretation from these trials and combining these results with previous years' results is currently underway. Refined results will be updated on this site when the process is complete. The Sugarbeet Research and Education Board of Minnesota and North Dakota and Minnesota's Agricultural Fertilizer Research and Education Council partially fund this research.

This research was conducted in collaboration with:

  • John Lamb, Department of Soil, Water & Climate, CFANS, St. Paul Campus – Lamb replicated the trials comparing urea to polycoated urea, spring vs. fall nitrogen applications, and some nitrogen applied as a sidedress in the sugar beet growing areas in central Minnesota (Southern Minnesota Beet Sugar cooperative growing area). The results were similar to those of the Red River Valley.
  • Katy Smith, UMC – Smith monitored nitrogen gas, methane, and carbon dioxide emissions from one of the trials in the Red River Valley. These gases were monitored to estimate nitrous oxide emission potential representing denitrification losses of nitrogen from the field. To this point, results suggest there might be some difference in denitrification among the treatments, but overall there was little denitrification loss during the three years of the trial. Combined with the low nitrogen required for maximum yield, there was apparently much less nitrogen loss from these sugar beet fields than we hypothesized from previous research.

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