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9 Tips for growing soybeans a second or third year

DarcyMaulsby/iStock/ThinkStock soybean pods closeup
While not encouraged, if you’re going to grow soybeans on the same field for multiple years, take these ideas into consideration.

Source: Cool Bean

According to the USDA, soybean acres will surpass corn acres in 2018. And some of those will be from second-year soybeans. University experts at have some tips and best management practices for those who may be planting second- or third-year soybeans.

  • Balancing short-term versus long-term profitability(i.e. economic sustainability). Short-term profitability may drive some farmers to consider planting more soybeans in 2018.  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 continuous soybean for the yield to drop to within 7% of continuous soybean (20+ years) yield levels whereas 2nd year soybean yielded within 5% of 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 7+ bushel-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? Experts would stick to rotations on 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 varietythan was planted in that field last year and make sure it has strong disease resistance traits to the problems in that field! Every variety has a weakness and planting the same variety on the same land two years in a row will expose that weakness.  Note that these varieties must be truly different.  The same soybean in a different color bag will greatly increase your risk of disease losses.  Please see the 2017 Wisconsin Soybean Variety Performance Trials for information.
  • Test for SCNand select SCN-resistant varieties. SCN proliferates in long-term soybean cropping systems.
  • Be prepared to scout your fields more intensivelyto 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 treatmentat 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. Growers are going to want to cut back on inputs but 2017 brought us above trend yield. 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.
TAGS: Management
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