Agronomic Considerations for Dealing with Unharvested Sugarbeets

Destroying Unharvested Sugarbeets

• Sugarbeets can survive the winter, under certain conditions, in the Michigan/Ontario growing area.
• Suggestions to minimize the risk of "weed sugarbeets" in 2009 include:
  • Choose a tillage method that will chop up the beet.
  • If feasible, leave conventional beets (rather than Roundup-Ready beets) unharvested to improve spring herbicide options if there is regrowth.
  • Defoliating is an added expense, but will expose the crown to freezing temperatures sooner. Any fall regrowth of shoots would deplete root reserves, while intact tops could add to root reserves if extended mild fall weather occurs.

Cropping Considerations After Unharvested Sugarbeets

Soybeans:

• This appears to be the best choice following unharvested sugarbeets. It does not appear that any special management practices would be required, based on research results.
• In Ontario, soybeans grown after waste beet spreading in 2005 did not exhibit adverse effects as long as the beets had been spread in mid-April or earlier. Unharvested sugarbeets will have an even longer time period for breaking down before soybean seeding.
• Corn:
  Corn growers may have experienced the "corn after beets syndrome" (stunting, purpling, reduced vigour). This would be expected to be more severe after unharvested beets.
• If you are planning to plant corn in this situation, a generous starter fertilizer program that includes some nitrogen to account for any early temporary nitrogen tie-up by the decomposing beet residue and some phosphorus to help address the "corn after beets syndrome" would be advisable.
• Most importantly, plan to do a pre-sidedress nitrogen test (PSNT) to determine nitrogen sidedress needs.

Seed Corn:

• This crop would not be advised after unharvested sugarbeets.

Spring Grains:

• Although these are good choices following unharvested sugarbeets, they are not commonly grown in significant acreages in the Ontario sugarbeet growing area.

General:

• The more the sugarbeets are cut up and exposed to the soil and winter conditions, the less the effect on the following crop, based on experiences in other growing areas.
• By leaving the 2008 crop in the field, normal crop removal of phosphorus and potassium is not occurring. These may be the fields where you can avoid additional P and K fertilizer expense in 2009. Look at recent soil tests for these fields. Fall 2008 or spring 2009 soil tests, however, will not accurately show the nutrient content that is still tied up in the relatively fresh sugarbeet residue.
• There may be a temporary early-spring tie-up of nitrogen as rapid root decomposition occurs with the first warm temperatures.
• In Ontario research with waste beet spreading in 2005, beets that were spread in January and exposed to winter soil conditions were in a more advanced state of breakdown by spring than fields that had beets applied in May.
• Beets cut up and mixed by fall tilllage can be expected to experience significant dessication and breakdown over an open winter with many freeze/thaw cycles; possibly less so if significant snow cover persists. This earlier breakdown should result in less nitrogen tie-up and earlier nitrogen release than would have been experienced with spring application of waste beets (or than would be experienced by a more frozen Minnesota/North Dakota winter).
• In Ontario conditions, nitrogen released in the fall or through mild winter periods can be lost to leaching.
• In Ontario greenhouse experiments in 2005, emergence of corn, soybean, and winter wheat was poor where concentrated sugarbeet residue had been applied. Potential problems could be minimized by tillage that produces smaller pieces and mixes the residue well with the soil.