Terry Aukes knows his soybean  seed . He evaluates soybean seed both personally as a farmer and professionally as seed department manager at Farmers Elevator Cooperative, in Larchwood, Iowa. “Match your choices to your toughest areas, and extract what you can in yield," he says. There is so much germplasm available to consider, and your choice should help you maximize each field's return on investment. There is so much yield variability, even among similar maturities.”
The challenge, says Fred Below, University of Illinois crop physiology researcher, is that many farmers do not pay enough attention to soybean selection. "They pay huge attention to corn selection, but seem to think they will get the same yield with soybeans regardless of the variety or maturity they choose; that is clearly not true.” You can increase soybean yields both through variety selection and better crop management, he says.
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Below's research confirms farmers can better maximize genetic yield potential by selecting varieties that respond to increased management. Soybean yields can vary by as much as 20 bushels per acre, grown in the same location, depending on variety, according to University of Illinois Variety Testing results.
Just as with corn  hybrids, proper soybean variety selection based on success in a management-intensive, high-yield potential production system is critically important, he says.
Below has compared full-season varieties in high-tech systems to more typical maturities in standard systems. He finds using a full-season variety in a high-tech system allows a longer period of vegetative growth for greater responsiveness to fertility and foliar crop protection. Of the 12 traited varieties with similar maturities from five different brands planted in 2012, yields ranged from 54.4 bushels to 66 bushels per acre in the high-tech setting. Longer maturity varieties averaged more than 3 bushels better than normal maturities.
Similarly, DuPont Pioneer uses local IMPACT (Intensively Managed Product Advancement Characterization and Training) trials to characterize varieties that will perform consistently on a range of environments in an area. Jan Jackson, IMPACT field testing lead for the northern business unit, says they test close maturity groups together; for example, a plot may contain late Group I, early and mid Group IIs. Generally, 40-50 variety comparisons are made per plot, and are placed in various environments to get a strong sense of performance against challenges.
"Yield differential can be sizeable within maturities," Jackson confirms. "If we compared only SCN-resistant varieties in a susceptible area, we might see a tight range of 5 bushels per acre difference. In areas without that susceptibility, yields from similar maturities might range by up to 10-15 bushels per acre.” Outside forces like cyst steal away yield potential, so select according to your circumstances, he says.
Aukes, the southwest-Minnesota farmer and seed-department manager, plants soybean variety blends. He planted WinField Precision Pak soybeans (PrPak) this season, a 50-50 blend of two soybean varieties of the same maturity. One variety is defensive and one is an offensive variety.
"Planting two varieties blended together addresses the variability in our fields," says Aukes. "In our cooperative's test plots, the blended seed has out-yielded each of the varieties on its own by 1-2 bushels per acre. That is quite a bit to me at current soybean prices."
Iowa State University research several years ago looked at different variety combinations blended at different percentage levels. "The premise is that two same-maturity varieties, given the unknowns of a growing season, can buffer the effects of weather and other stresses," says Eric Bartels, WinField product manager for western Iowa and southwest Minnesota. "Yields show one component is better than the other in any given area. But across the field, the synergies of the two bring up the field average to optimize all the acres."
Yield differences vary by field
Bartels says yield differences farmers may see planting PrPaks vary by field, as verified by WinField's Nationwide Answer Plot program, but he notes farmers with the most highly variable conditions will see the biggest bang for the buck. "That's where we see the greatest value, although every year and every field is different," he says. "This unique strategy can help you maintain yields on tough acres and capitalize on the highest potential on better areas."
Fred Below is testing four PrPak blend varieties this season for yield. His work is part of his "Six Secrets of Soybean Success" multiyear research effort to help farmers get more yield by identifying better management strategies. He places variety selection third in priority order of the six factors, but says he could easily move the factor to No. 2 with closer attention to fertility needs in conjunction with variety selection.
"We know variety selection is most important when combined with fertility and row spacing," he says. "In the nearly 12-bushel-per-acre swing across varieties of similar maturities in six Illinois high-technology plots last year, fertility produced the most yield difference across locations. The high-tech system mitigates other factors, although the drought may have limited the yield swing in 2012."
He encourages farmers to improve soil fertility through balanced crop nutrition and fertilizer  placement technologies to get the most out of the full-season varieties chosen.
"Soil fertility is the most overlooked component of soybean management for high yield," says Below. “Phosphorus, in particular, can be immobilized in soil and might not be available in sufficient quantities for modern soybeans. High-yield potential management systems (70 to 80 bushels per acre) remove as much phosphorus from the soil as does 150-bushel corn. Our work with corn has shown that spring placement of phosphorus in a band 4-6 inches beneath the row improves early plant growth and vigor. We anticipate a similar response for soybeans."
Other newer technologies – such as biological seed treatments that establish favorable relationships between the soybean plant and microorganisms – could also be a management strategy for enhancing uptake of critical nutrients like phosphorus and nitrogen. Below recommends complete seed treatments, particularly for farmers who plant early in the season. Fungicide, insecticide and nematicide treatments added an average 2.6 bushels per acre to yield in 2012.
Six secrets of soybean success
Fred Below, University of Illinois crop physiologist, identifies the following six management strategies as key to soybean success:
- Use crop management to mitigate the negative impacts of weather-induced variations in soybean yields that you cannot control.
- Improve soil fertility through balanced crop nutrition and fertilizer placement technologies.
- Maximize genetic yield potential by selecting varieties that respond to increased management.
- Protect yield potential and maximize seed fill by using foliar fungicides and insecticides.
- Enhance seed emergence and vigor through the use of fungicidal, insecticidal and plant growth regulator seed treatments.
- Use narrow row spacing for maximum light interception and optimized fertilizer placement strategies in corn-soybean rotations.
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