In response to producer questions, this article addresses planting and economic considerations for planting soybean after soybean in 2017. In Part 2, we share considerations for in-season management.

A recent USDA report shows Nebraska soybean planting is expected to be up nearly 10% from last year.  This increase in soybean acres could come from any of the following rotation changes:

• Situation 1: Shifting a corn-corn (C-C) field to a corn-corn-soybean (C-C-S) field in 2017. 
• Situation 2: Shifting a soybean-soybean (S-S) field to a soybean-soybean-soybean (S-S-S) field in 2017.
• Situation 3: Shifting a corn-soybean (C-S) field to a corn-soybean-soybean (C-S-S) field in 2017.
• Situation 4: Converting wheat and/or sorghum acres to soybean in 2017.

More articles in this series

Rotation Considerations

A series of long-term rotational studies from Wisconsin and Minnesota  have been conducted through the years comparing continuous corn, continuous soybean, corn-soybean rotation, and five years of corn followed by five years of soybean (Crookston et al 1991, Porter et al 1997, Pedersen & Lauer 2003).  Results, summarized in Table 1, have consistently shown:

• First year soybean following five years of corn consistently yielded the highest through the years (Situation 1 above).  
• Second year soybean often yielded similar to soybean in the corn-soy rotation (Situation 3 above).  
• Third-fifth year soybean yields were similar to those of continuous soybean (Situation 2 above).  

Another Wisconsin study from 2009-2011 conducted within the long-term rotational study mentioned above, showed the following soybean yields five years in a row after five years of continuous corn: Year 1: 56.8 bu/ac, Year 2: 54.6 bu/ac, Year 3: 55.8 bu/ac, Year 4: 53.6 bu/ac, and Year 5: 51.6 bu/ac. The soybean-corn rotation yielded 56.2 bu/ac (Marburger, et al., 2016).

A corn-corn-corn-soybean-soybean rotation study (Irmak et al., 2014) showed 10 out of 11 irrigation treatments resulted in greater grain yields with soybean following soybean at Clay County. The all-treatment average grain yield was 70 bu/ac in the first year and 73 bu/ac in the second year, with some treatments having over 11 bu/ac greater yield with soybean following soybean after three consecutive years of corn. A nine-year University of Illinois study also found increased soybean yields with a corn-soybean-soybean rotation (57.9 bu/ac) compared to corn-soybean (52.5 bu/ac) at one location. (Situation 3 above)

When comparing continuous corn or soybean rotations, a recent journal article (Seifert, et al) looked at yields, soil and weather conditions, and crop histories across the Midwestern U.S. and found an average continuous corn yield penalty of 4.3% and a continuous soybean penalty of 10.3% from 2007-2012. (Situation 2 above)

Data collected from long-term experiments show that soybean following corn in a two-year corn-soybean rotation out yields soybean in a continuous soybean sequence by 5% to 15%, as summarized by Fox et al., 2013. This is consistent with recent data reported by University of Wisconsin researchers.

See the individual studies referenced in this article for additional details on material and method and statistics.

**Penalty from growing continuous soybean compared to corn/soy rotation in data averaged over six states.

Considerations on Highly Erodible Land

Please contact your local USDA-NRCS Resource Conservationist to communicate the temporary change in the conservation plan (crop rotation, tillage, etc.) on file for your highly erodible land (HEL) fields. There is increased risk of ephemeral gully erosion from fall and spring rains in HEL fields when planting soybean after soybean.

Variety Selection

Variety selection is an important management decision whether planting soybean after corn or after soybean. Listen to agronomist and Nebraska Extension Educator Nathan Mueller discuss variety selection down to the field level. Selecting soybean varieties for disease resistance becomes a higher priority in continuous soybean. If your field has tested positive for Soybean Cyst Nematode (SCN), it will be important to use varieties resistant to this pest and to rotate the sources of that resistance. You need to also weigh the importance of other varietal resistance differences for diseases like Phytophthora, Sudden Death Syndrome (SDS), and for disorders such as iron deficiency chlorosis (IDC).

Production Factors

Planting date, seeding rate, and inoculant are important factors in soybean production and economics regardless of cropping system. Planting in late April to early May in Nebraska is the primary way to increase soybean yields. In some situations planting fewer acres of corn may allow earlier soybean planting. Additional savings of nearly $10.60/acre can be achieved by reducing soybean seeding rates from 150,000 seeds/acre to 120,000 seeds/acre. Most of this work was conducted in corn-soybean rotations. UNL researchers don’t recommend inoculant in medium to heavy textured fields where soybeans have been planted in the past three years and no drought or flooding occurred. In most soybean-after-soybean sequences, inoculation would not be necessary.  

Economic Analysis

Table 1 provides an economic analysis of planting decisions in 2017 based on current crop and previous crop planted. Prices and costs were from the Nebraska Extension 2017 Crop Budgets. These budgets can be downloaded in PDF or in an Excel format that allows you to input your costs.

* Prices used for corn and soybean are estimated market year price for 2017 from the WASDE report, April 11, 2017. 

Summary

The rotation research cited shows highest soybean yields are obtained after several years of corn.  Yields of second year soybeans are similar to those of soybeans in a corn-soybean rotation.  Yields of third to five year soybean are similiar to continuous soybean and subject to potentially greater yield penalty. Variety selection and rotation of resistance traits such as SCN are important. Likewise, selecting fields that are highly productive or historically have higher yields would be a good choice for soybean after soybean.

When considering the economics using Nebraska Crop Budgets and April 2017 WASDE prices, non-irrigated soybean following corn is the most profitable rotation followed by non-irrigated no-till soybean following soybean.

See Part 2 of this article for information on in-season management considerations with soybean-after-soybean.

References

Conley, S.P., S. Naeve, and John Gaska.  2016.  Best Management Practices for Growing Second Year Soybeans, The Soy Report, University of Wisconsin.

Crookston,R. K., J. E. Kurle, P. J. Copeland, J. H. Ford, and W. E. Lueschen. 1991. Agronomy Journal 83:108-113.

Elmore, R., J. Specht, J. Rees, P. Grassini, and K. Glewen.  2014.  Why Planting Soybean Early Improves Yield Potential, UNL CropWatch.

Fox, C.M., T.R. Cary, A.L. Colgrove, E.D. Nafziger, J.S. Haudenshield, G.L. Hartman, J.E. Specht, and B.W. Diers.  2013.  Estimating Soybean Genetic Gain for Yield in the Northern United States-Influence of Cropping History, Crop Science.

Grassini, P., B. Farmaha, J. Specht, T. Hoegemeyer, and R. Elmore.  2017.  Rotation Impact on Irrigated Corn and Soybean Yields in Nebraska, UNL CropWatch.

Hicks, D.R. and T. R. Hoverstad.  The Rotation Effect for Corn Yields. 

Irmak et al., 2014. Soybean Yield, Evapotranspiration, Water Productivity, and Soil Water Extraction Response to Subsurface Drip Irrigation and Fertigation, University of Nebraska-Lincoln Department of Biological Systems Engineering.

Lauer, Joe.  2015.  The Corn-Soybean Rotation X Tillage Interaction: No Tillage Required When Rotating. University of Wisconsin.

Marburger, D.A., S. Mourtzinis, J.M. Gaska, and S.P. Conley.  2016.  Do Crop Rotation and Tillage Influence Soybean Seed-Applied Inoculant Decisions?  Agronomy Journal 108:402-406.

Mueller, N.  2016.  Soybean Variety Selection (Market Journal video).

Mueller, N., R. Elmore, C. Shapiro, J. Rees, and L. Thompson.  2017.  Making Data Driven Decisions for Soybean Inoculation, UNL CropWatch.

Nafziger, E., E. Adee, M. Johnson, B. Mansfield, A. Peltier.  2013.  Can We Rotate Our Way to Higher Crop Yields?, University of Illinois.

National Ag Statistics Service.  March 31, 2017.  2017 Nebraska Prospective Plantings. 

Pedersen and Lauer.  2003.  Corn and Soybean Response to Row Spacing, Rotation, and Tillage.  Agronomy Journal 95:965-971.

Porter, P.M., J.G. Lauer, W.E. Lueschen, J.H. Ford, T.R. Hoverstad, E.S. Oplinger, and R.K. Crookston.  1997.  Environment and the Corn-Soybean Rotation Effect.  Agronomy Journal 89:442-448.

Rees, J., L. Thompson, K. Glewen, G. Zoubek, N. Mueller, and B. VanDeWalle. 2017. 10 Years of Research Shows Benefit of Reducing Soybean Seeding Rates, UNL CropWatch.

Seifert, C.A., M.J. Roberts, and D.B. Lobell.  2017. Continuous Corn and Soybean Yield Penalties across Hundreds of Thousands of Fields, Agronomy Journal109:541-548.

Sindelar, A.J., M.R. Schmer, V.L. Jin, B.J. Wienhold, and G.E. Varvel. 2015. Long-Term Corn and Soybean Response to Crop Rotation and Tillage.  Agronomy Journal 107:2241-2252.