Indeterminate soybeans can add nodes through the R6 reproductive growth stage, which creates additional potential for yield development. By keeping insects and diseases in-check late in the season, you can take advantage of the opportunity to boost yields.
A common assumption is that indeterminate soybeans are done creating yield by the R6 reproductive growth stage. Most of the time, that’s simply not the case, according to Brad Beutke, an agronomist with Crop Tech Consulting, based near Heyworth, Ill.
"You don’t want to make the mistake of walking away from soybeans too early," he cautions.
Instead, he tells farmers to continue scouting soybeans for insects and disease pressure through R6, and to consider treating the crop if problems with either issue accelerate. In addition, irrigating the crop up to R7, until the leaves practically fall off, is usually a financially positive decision as well. The reason: "We’re pulling in the final 20% of dry matter into the seed itself at that point," Beutke explains. "From a management standpoint, do whatever you can to eliminate stress late in the season to hold onto those pods."
Beutke shared that message with consultants and farmers attending the Farm Journal Corn College near Coldwater, Mich., earlier this week. In addition, Beutke taught attendees how to stage soybean plants, essentially determining the specific point of development of a soybean plant in order to make agronomic decisions.
"It’s important to know how to determine specific soybean growth stages, especially once the plants reach the reproductive stages, so you can determine treatment thresholds for insects and disease," he explains.
In the vegetative growth stages, you can gain some insight on soybean root development and how well the plant is producing its own nitrogen. However, vegetative stages are not nearly as important to soybean yield as the reproductive stages.
In an "average" year, Beutke says the majority of yield potential in soybeans is produced in the middle and upper middle portion of the crop.
"The middle parts of the plant have good trifoliates and create a lot of energy, while the lower trifoliates are typically shaded and drop off," he says. "The top third of the plant, in indeterminate beans, keeps adding nodes to the plant, so you can build more beans high up in the canopy and increase yield."
That is not the case with determinate soybeans, Beutke adds. "Once your crop reaches the reproductive stages, you are not able to add nodes or additional yield," he says. "At that point, you’re simply trying to protect yield."
Thank you to the 2014 Soybean College sponsors:
BASF, Great Plains Mfg., Honeywell, Plant Tuff, SFP, Top Third, Wolf Trax