Soybeans had a really good year in 2016, says Emerson Nafziger, University of Illinois Extension agronomist. “In the last five years, soybean yields have gone up 4 bushels per acre per year in Illinois.”

Nafziger gives credit to the weather, genetics and good management. “I don’t think we can expect 4 bushels an acre a year for the next 10 years, but we’ll take it when we can get it,” he says.  

Even though he expects yield increases to slow some, Nafziger says managing crops according to expected weather conditions is key. He shares six findings from the 2016 season and agronomic recommendations for soybeans next year:

1. Mother Nature still rules. Nafziger gives the “favorably average” weather conditions primary credit for the outstanding 2016 crop. Soybeans started strong, with just enough rainfall in May. A warm and dry June resulted in a good canopy and roots, and soybeans flowered a little earlier than normal. July tended toward wet, and August started out on the dry side — but then rains returned. Soybean plants responded with excellent seed fill from an outstanding canopy, he notes.

2. Timely planting sets the stage. Soybeans planted in late April outyielded late-May plantings by setting the crop up for ideal weather conditions during pod set and seed fill, Nafziger notes. He advises planting soybeans from mid-April through early May, as weather and field conditions allow.

3. Rotation creates complications. Nafziger says soybeans following several years of continuous corn topped crop rotation trials this year, averaging 10 more bushels per acre. But continuous soybean yields were lower than in previous years. Nafziger speculates that soil microbes play a role in both phenomena and hopes to study this further.

4. Seeding rate sweet spot tough to pinpoint. Stands were consistently 85% of seeding rates in his trials in 2016, but Nafziger found that the plant stand needed to produce the best yield varied widely — from barely more than 50,000 at one site to more than 190,000 at another. Just as surprising, there was no relationship between yield level and optimum population. He recommends a seeding rate of 140,000 to 150,000 per acre, noting that this should provide enough plants in the majority of fields.

5. Jury still out on nitrogen and soybeans. Nitrogen at planting in an irrigated field with lower organic matter showed a 20-bushel-per-acre advantage in 2016, Nafziger notes. However, he adds that the majority of other trial locations across the state indicated soybeans had little to no response to nitrogen. For most fields, adding nitrogen is unlikely to provide an adequate return on investment.

6. New tech is not a drag. Nafziger reports that new Roundup Ready 2 Xtend soybeans performed as well as or slightly better than RR2 soybeans in the majority of University of Illinois variety trials. LibertyLink varieties also performed well in the trials.

“The genetic improvement in soybean continues, and I think it’s been responsible for a good chunk of yield improvements we’ve seen,” Nafziger says. “But genetics, the weather and management all work together to produce the yields we get. Today’s varieties are more efficient in using resources, so we may not need to increase inputs, even at higher yield levels.”