Soybeans Following Soybeans

  • High soybean prices relative to corn can favor shifting acreage away from corn to more soybean production.
  • In some cases, this may involve planting fields to soybeans in two consecutive years.
  • Planting soybeans in the same field in consecutive seasons is generally not recommended by extension agronomists; however, there are several management considerations that can help maximize productivity for growers pursuing this strategy.

Yield Potential

  • Growers should expect lower yields in second year soybeans.
  • Research results have varied, but a yield reduction of 3-5% compared to soybeans following corn is not an unreasonable expectation.
    • 2.3% average yield reduction in an 8-yr Univ. of Kentucky study with individual year reductions up to 13% (Grove, 2017).
    • 6.5% average yield reduction in a 4-yr study in Ontario
      (OMAFRA, 2009).
    • 0% average yield reduction in a long-term Univ. of Wisconsin study (Lauer et al., 1997).
  • Plant stress caused by environmental conditions, diseases, weed pressure or insects can easily increase yield losses in second year soybeans
     

Management Considerations

Field Selection

  • Avoid poorly-drained soils due to higher risk of Pythium, Phytophthora, sudden death syndrome, and brown stem rot. 
  • Avoid fields with herbicide resistant weed species and fields where white mould has been a concern.
  • Consider cover crops in fields with slopes prone to erosion – soybeans produce less residue than corn and decompose more quickly.
     

Variety Selection

  • Avoid planting a field to the same soybean variety two years in a row.
  • Select soybean varieties with high levels of disease resistance.
  • Test for SCN and select SCN-resistant varieties, be sure to rotate resistance sources.
    • SCN proliferates in long-term soybean cropping systems.
    • Resistant varieties can reduce SCN reproduction by 70-80%.
       

Seed Treatments

  • Use a fungicide seed treatment to protect against diseases such as Pythium and Phytophthora that can increase in severity under continuous soybean production.
  • Pioneer® brand soybeans treated with ILeVO® fungicide seed treatment provides control of sudden death syndrome and certain soil-borne nematodes such as soybean cyst and root knot nematodes.
    • Soybeans treated with ILeVO fungicide treatment produced significantly higher grain yield (4.9 bu/acre) in high SCN environments in Pioneer testing (O’Bryan and Burnison, 2016).
    • In moderate SDS environments the addition of ILeVO fungicide treatment increased grain yield 4.5 bu/acre.
       

Soil Fertility

  • Growers often routinely rely on carryover fertilizers for soybean when rotated with well-fertilized corn.  Soybean after soybean may require additional fertilizer, especially potassium.
     

Disease Management

  • Many diseases can overwinter on soybean residue, some can be managed with fungicide, some cannot.
  • Stem canker and pod and stem blight can overwinter on residue but fungicides are not as effective on these.
  • Septoria brown spot and frogeye leaf spot are two diseases that can be managed with foliar fungicides.
  • Scout fields regularly to check for disease problems.
     

Weed Management

  • Any weed escapes in the previous soybean crop are likely to result in greater weed management challenges in second-year soybean.
  • Use multiple modes of action
  • Soil residual herbicides applied pre-emergence and with a post-emergence application can help manage problem weeds.
     

Authors: Dan Emmert and Mark Jeschke

March 2017

References

Grove, J. 2017. Yield penalty from second year soybean. Univ. of Kentucky. https://graincrops.blogspot.com/2017/01/yield-penalty-from-second-year-soybean.html

Lauer, J., P. Porter, and E. Oplinger. The corn and soybean rotation effect. Univ. of Wisconsin. http://corn.agronomy.wisc.edu/AA/A014.aspx

O’Bryan, K. and M. Burnison. 2016. Performance of soybean seed treatments against SDS and SCN in on-farm trials. Pioneer Agronomy Research Update.

OMAFRA. 2009. agronomy guide for field crops. http://www.omafra.gov.on.ca/english/crops/pub811/2tillage.htm

Image courtesy of Case IH.