Is 2016 the year to grow more soybeans in rotation?

Commodity prices are low, production of corn and soybeans is high (particularly for corn), and growers want to both ensure a profit as well as save money. Is there an opportunity to grow more soybeans in a rotation and is a there a soybeans-on-soybeans yield penalty?

For years we have thought that the yield penalty for growing continuous soybeans was greater than for growing continuous corn. The reason was a buildup of soil pathogens that knocked off seedlings and led to poorer plant health. I have often wondered if this was myth or reality because most growers in the Corn Belt never have tried continuous soybeans, yet aren’t reluctant to grow corn two or more years in a row. I tend to believe it is more myth than reality, but like corn it takes extra awareness and management to make it work.

Greg Anderson, a rain-fed farmer from Newman Grove in northeast Nebraska, doesn’t believe there is a continuous soybean penalty. He has been growing 100% continuous soybeans on over 1,000 acres for 26 years. Anderson is very active in the soybean industry, having been on the Nebraska Soybean Board from 1993 to 2005, director at the United Soybean Board from 1999 to 2008 (Chairman in 2005), and back on the Nebraska board beginning in 2014. You could say he has soybeans in his blood, loves the crop and wants to help the industry.

I knew Anderson grew continuous soybeans and over the years media have written on his approach and success. He has told me on several occasions that his soybean yields continue to increase. “My yields are always above the Nebraska state dryland average and always above the county average. What’s important is that yields are not just maintaining, but are increasing.”

So why does he grow continuous soybeans? “As a smaller farmer who works alone, this system is easier to handle and less labor intensive (than corn). I can harvest earlier and am out of the field sooner in the fall. And when Roundup Ready® soybeans came available, growing continuous beans became much easier.”

Of course, he emphasizes that there is less grain to haul, no drying and fewer inputs to purchase. “The system is not going to gross the same as corn, but there is less expense and it is profitable.”

Anderson’s environment is different than Illinois’ since it is drier. His soils are lighter, similar to the timber soils of southern Illinois, and tend to be droughty. Think silty clay loam with a fairly high percentage of clay that forms a tight soil structure.

Anderson is a no-tiller, planting with a Krause® no-till drill in 10-inch rows at a seeding population of 165,000 with a soybean metering mechanism. He also broadcasts dry fertilizer each fall. The steps he follows to succeed in growing continuous soybeans?

1. Pay close attention to soil fertility
2. Choose best yield genetics
3. Don’t rely on a single seed brand, choose the best bean
4. Plant in narrow rows and at a higher population
5. Plant early; start April 20 to get the crop off to an early start
6. Treat seed to plant earlier and protect seed to get it out of the ground
7. Inoculate seed with rhizobia
8. Have a plan to apply an insecticide on aphids based on scouting thresholds
9. Have to think about white mold in wet years (Anderson hasn’t yet had an outbreak)
10. Apply a foliar fungicide at R3 depending on the year

“Key is managing the soil and fertility and keeping up fertility,” said Anderson. “Beans aren’t a scavenger crop and don’t have the root mass of corn, so growers need to feed beans like they feed their corn crop. I always add some trace (minerals) including zinc and ½ lb. boron.” However, he hasn’t applied foliar nutritionals yet.

His advice? “It takes the right soils to grow continuous soybeans. They have to drain, you need to keep the pH between 6.5 and 6.8, and organic matter needs to be high (his soils are now above 4% with no corn or wheat in the rotation). Continuous soybeans aren’t for everyone, but it works for me. Growers have to find the places that it will work and avoid fields where it won’t.”

If you have grown continuous soybeans anywhere in Illinois we would like to hear how they fared, what you did to make the system succeed or why you feel the system failed.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com or leave a comment below.