Innovations in the Field

Sponsored by BASF

This yearlong endeavor looks at how four farmers are evaluating technology and agronomic information that can boost the productivity of their operations.

The 100-Bushel Soybean Playbook

by Patrick R. Shepard

Brad Koen (right) worked with Heath Whitmore to design a cover-crop program that fits his minimum-till/no-till system. PHOTO: LANCE MURPHEY

Soybeans can be unpredictable. Lately, growers have been achieving more consistency and breaking the yield threshold through the use of well-timed management moves. Brad Koen is one of the agronomists helping Arkansas growers push soybeans toward the 100-bushel yield goal. The former University of Arkansas agronomist and private consultant and now, a BASF Innovation Specialist, offers several field-proven soybean management plays:

Plant early

"If you could change just one thing in your soybean operation that would help increase your yield, it would be plant earlier," says Koen. "I like to see growers [in the Mid-South] start planting beans the first week in April and finish by May. We typically start with mid-Group IVs, and switch to Group Vs in May."

"I think you have more yield potential with Group IVs planted early, but they're not going to sit in the field waiting for you. When they're ready, you have to get in there and cut them," Koen adds.

"We also plant less seed than many other growers who plant early in the year. We've been planting between 130,000 and 140,000 seed per acre. Planting earlier gives you more sunlight and more days to move your crop through the growth stages. It gives you more time for vegetative growth, so you don't want a lot of plants crowded together and competing against each other because then they'll grow real tall and lodge on you. Conversely, when we plant later in the season, we want a thicker population so the plants will compete and grow taller."

Supplement nitrogen

Koen has seen an 8-bushel increase by aerially applying 45 units of nitrogen at the R3 growth stage. He recommends using a prill urea with a urease inhibitor. "By the time the nitrogen gets rained or irrigated in, the crop is at about R4 or R5, which is when the plant needs the supplemental nitrogen," Koen explains. "The timing of application is critical. If you apply too early, the soybean plant becomes lazy and reduces its own production of nitrogen, which is extremely important. A soybean plant makes about 65% to 70% of its own nitrogen. The rest of the nitrogen is mined from the soil."

Soils with low organic matter seem to respond best to supplemental nitrogen, he says. "After further research, we found that any time our organic matter was less than 2.5%, we averaged 8.3 bushels increase per acre by applying nitrogen at R3. Any time it was over 2.5% organic matter, we averaged only 1 bushel per acre."

High-yield soybeans can also suck up potassium. Koen notes that a 60-bushel bean crop can remove about 75 pounds of potassium per acre. "If you're cutting 100-bushel soybeans, you're removing close to 100 pounds of potassium," he adds. "As we increase our yields, we have to increase our fertilizer applications."

Fine-tune fungicides.

Koen likes to see beans growing and green all the way to harvest. If beans begin drying down too early, he says growers miss out on yield. "You need the bean to finish developing, because that late-season weight is where much of your extra yield comes from," he explains. "In our high-yielding fields, beans will often remain green a week to 10 days longer than the check plots beside them."

Koen adds that the R3 nitrogen application helps soybeans stay green and healthy longer, but he also suggests sequential fungicide applications when shooting for higher yields.

"We apply the first shot of Priaxor at R3 and follow with the second in two to three weeks at R5. We overlap our fungicides so the plant does not stress due to disease or other environmental conditions. Even with no diseases present, we see an extra 4 to 6 bushels on a single application of Priaxor, and an extra 10 to12 bushels with two applications. This increase is due to the plant health benefit of Priaxor. It improves photosynthesis and leaf health, which equates to improved yield potential. It also aids in the soybeans handling stresses such as drought," he says.

Decide on desiccants. Pushing soybeans to the max can result in green soybeans late in the year. Spraying a desiccant to knock the leaves off has become a more popular management tactic in these situations. Koen says the good news is that also means yields are apt to be good in those scenarios.

Use seed treatments

Koen notes that University of Arkansas entomologist Gus Lorenz's research on seed treatments that include both an insecticide and a fungicide show a positive economical return-on-investment about 70% of the time. "That's impressive," Koen says. "We started using seed treatments and found we got a better stand and a healthier start."

Narrow the bed.

The narrower the rows, the better. Koen recommends switching from 38-inch beds to 30-inch beds. "You can accomplish the same thing if you twin-row a 38-inch bed, essentially having a 30-inch bed," he adds.

Manage irrigation

Koen believes row water is the most efficient way to irrigate in the Mid-South. During extremely hot summers, pivots have a difficult time getting enough moisture down to the soil line. "We mainly grow indeterminate beans that continue adding new blooms and growing," he says. "So I do not like to see irrigation during the vegetative growth stages unless we're in a droughty situation that might cost us some plants. It's also important to avoid overwatering."

Pester the pests

Weeds in soybeans mean lost yield, and Koen is a big fan of overlapping residuals. For example, he suggests applying Verdict at planting and coming back over the top about three weeks later at the V3 stage with Roundup and Zidua. "That's a great system for controlling glyphosate-resistant marestail and pigweed," he says. "If you do get some escapes, you still have the flexibility of applying a contact herbicide like fomesafen."

"Likewise, we can't allow insects to nibble at yields. We begin at planting with an insecticide on the seed and scout weekly and treat at economical thresholds."

For more information on developing a high-yield soybean strategy, contact Koen at