Describing super soybean yields: It's complicated
Fungicides? How about seed treatment? Or foliar nutrients. Inoculants, anyone?
While you might think those are the ingredients for higher-yielding soybeans, you'd only be partly correct. Growers need to first focus on the old-fashioned stuff: good variety selection, early planting, stress management, and good soil fertility. Then they may judiciously use the new stuff.
That's the advice from Shawn Conley, a soybean specialist at the University of Wisconsin-Madison. He knows that super yields are possible.
“We get 90 bushels per acre at some of our locations every year,” says Conley. That's about double the Wisconsin state average and the national average (41.5 bushels per acre in 2011).
Following are three common questions he gets at farmer meetings and his answers to those inquiries.
Q:I'm probably not going to get a 90-bushel-per-acre average, but I would like to boost average per-bushel yields from 45 to 55. How do I do it?
A: Start by identifying your soybean diseases, says Conley. Look for things like soybean cyst nematode, sudden death syndrome (SDS), white mold, and brown stem rot. You can find varieties that resist them or possess some level of tolerance to the common diseases in your fields. Find them and plant them.
“Really study the genetics when you make those selections,” he says. “With corn, some farmers will have 10 to 12 hybrids they choose from, but they only look at two or three soybean varieties. Sometimes, they just go with what their dealer has left over.”
Separate genetics from traits, he says. Genetics is where you actually get yield potential; traits just help protect that yield. Don't just select varieties that yield well in your local area and plot. Broaden your search to a variety of environmental conditions. You'll increase your chance for success, Conley says.
Don't ignore soil tests, either. Farmers fertilize for corn but not for soybeans. The fact is, high-yield soybeans use a large amount of potassium (K). Beans remove about 1.4 pounds for every bushel of grain produced. Plants deficient in K are more susceptible to some diseases and can be predisposed to increased aphid counts – all yield-robbers.
Low sulfur content may also limit soybean yields, particularly in a crop rotation including alfalfa. “Alfalfa is a big user of sulfur,” he says.
Q:When should I plant soybeans, and what maturities?
A: This can be the most important and least expensive cultural consideration that impacts soybean yield, says Conley.
“At our Arlington Research Station, we've seen an average yield loss of 0.4 bushels per acre per day when planting is delayed past the first week of May,” he says. This is because of decreased pod numbers, although soybeans will partially compensate through increased seed size.
Early planting increases risk for some seedling diseases, as well as brown stem rot and SDS. If you plant early, couple it with good disease-resistance management, including seed treatments.