Grower News: The Facts About Growing Second Year Soybeans

BY David Schiff | December 19, 2016 - 

This is a difficult topic to address because growing second year soybeans is not a best management practice. That said, economic realities and forecast pricing have many growers seriously considering making an exception.

In a recent article by Shawn Conley, Seth Naeve and Jon Gaska, they tackle the problem head on in responding to a post penned by Gary Schnitkey and Darrel Good entitled 2017 Crop Budgets and Current Prices Say Switch to Soybeans and Expect Low Yields.

Schnitkey and Good think farmers may plant 5 million more acres of soybeans in 2017 than in 2016 based price ratios and input cost. It’s a good bet many of these acres will be second year soybeans.

So  if you are considering second year soybeans, here are some recommendations to keep in mind. These points come directly from the article written Shawn, Seth and John:

  • Balancing short-term versus long-term profitability (i.e. economic sustainability). Short-term profitability may drive some farmers to consider planting more soybeans in 2017.  Data from our long -term rotation experiment clearly shows the benefit of crop rotation to the soybean crop. It is amazing that after 5 years of corn, it only took 3 years of soybean for the yield to drop to continuous soybean (20+ years) yield levels. Good news is that 2nd year soybean yielded the same as soybean in a corn-soybean rotation. We could hypothesize then that the yield of the 3rd year of continuous soybean (in our experiment) would be similar to a 2nd year of soybean in a corn soybean (C-S-S) rotation. Our data clearly shows that 3 or more years of continuous soybean gives you a 4+ bu per acre hit when compared to a corn-soy rotation and moves you close to that of continuous soybean. In short, you are setting your long-term profitability up for a hit. So what do you do? If it were my land I would stick to my rotations on my owned land and consider 2nd year soybeans on the rented ground.
  • Be aware that soybean after soybean will alter the pest complexes in your fields.  Some of these alterations may take years to undo as you will be making a long-term impact on your soil and resulting soil health. Also don’t automatically think that simply adding a cover crop to this S-S rotation will “fix” these issues.
  •  Plant a different variety than was planted in that field last year and make sure it has strong disease resistance traits to the problems you have in that field! Every variety has a weakness and planting the same variety on the same land 2 years in a row will expose that weakness.  Note that these varieties must be truly different.  The same bean in a different color bag will greatly increase your risk of disease losses.  Please see our 2016 Wisconsin Soybean Variety Performance Trials for information.
  • Test for SCN and select SCN resistant varieties. SCN proliferates in long-term soybean cropping systems. 
  • Be prepared to scout your fields more intensively to get ahead of any disease problems. Increased disease pressure may provide an opportunity to see yield responses from fungicides and insecticides.  You may need to include these costs into your original economic decisions.  
  •  Keep seeding rates lower if white mold was a problem in the field 
  • Use a seed treatment at the max a.i. fungicide rate. 
  •  Use a pre-emergence herbicide and use multiple modes of action. If you had weed escapes, expect even larger problems in soybean after soybean. 
  • Soil sample and replace K if needed: I know growers are going to want to cut back on inputs but 2016 brought us record yields. An 80 bushel soybean crop meant you removed ~98 pounds per acre of K20 equivalent fertilizer. Growers often routinely rely on carryover fertilizers for soybean when rotated with well-fertilized corn.  Soybean after soybean may require additional fertilizer, especially K. 

Again, planting second year soybeans is not a best practice. If you’re so inclined, these recommendations can help you make the best of a challenging situation.

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