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Research Highlights

Research Highlights
Michigan Researcher Focuses on Soybean Yield Potential with Several Management Strategies

Photo: United Soybean Board

By Carol Brown

The words ‘yield potential’ are key for crop farmers and thinking about yield potential is as important prior to planting as it is once the seeds are in the ground.

Michigan State University cropping systems agronomist Manindar Singh is conducting research to help soybean farmers improve yield potential across the growing season through several projects funded by the Michigan Soybean Promotion Committee. 

“I want to develop agronomic management guidelines that can optimize soybean productivity,” Singh says. “We are looking at management strategies to use before and at the planting time and identifying practices that will utilize the growing season to the full extent.”

Singh says the big picture is to improve farmer profitability, which is done by improving yield and maintaining low or reducing production costs. His research is focusing on a few main topics to help make the big picture clearer: the ideal planting time, maturity groups and seeding rates. The right combination of these variables could lead to high yield potential.

“The overarching goal is how can we close the canopy in soybeans earlier in the growing season, because in Michigan we are dealing with a relatively shorter growing season,” he says. “We have seen the trend of early planting over the last few years in the state and have found the optimal time for soybean planting is mid-May or earlier. We have seen an average increase of one to three bushels per acre with earlier planting from our 2019-2020 on-farm trials.”

If planting is delayed until closer to mid-June, yield can decline more than one percent per day. Singh saw that planting earlier than mid-May did not increase yield in their small-plot research. But when early planting is combined with a later maturity group, Singh saw benefits. 

Figure 1. Soybean Maturity Group selection yield by planting date at Mason, MI.

“If growers plant at the end of April or first week of May, we recommend selecting a later maturing variety to get more benefit from early planting,” says Singh. “For instance, Maturity Groups 2.2 to 2.5 are typical in our area, but if we push it another half or full maturity group, we’ve seen a yield increase of three to five bushels per acre.”

Singh explored other management strategies including seeding rate and row width and found that these could also affect yield potential. But the cost of seed needs to be considered for both of these strategies. 

“We found there is potential for growers to cut down on seeding rates without impacting their yield significantly,” remarks Singh. “There is quite a bit of difference if you are targeting maximum yield versus maximum profit. Let’s say we’re in mid-May and the seeding rate that would maximize yield is around 140,000 seeds per acre. But if we were to go for maximum income – the cost for planting the seed – the number is around 100,000 seeds per acre.”

Singh and his research team saw no benefit when using a high seeding rate with early planting. Yield was not reduced because the soybean plants were able to branch out. He did find that high seeding rates worked better at later planting times because of the shortened growing window. More plants in the field closes the canopy quicker, which impacts yield, he says.

Figure 2. Soybean seeding rate response.

This same thought process works for row spacing, with seed costs taken into consideration as well. In the shorter growing season in northern Michigan, Singh says 15-inch rows will also lead to a closed canopy sooner. But with narrow rows, white mold concerns arise, although he did not find disease pressure in his trials. 

“Even with narrow rows, you can cut down on seeding rates,” he says. “The canopy will be thin, and you will have more air movement and light penetration to help reduce white mold issues.”

Singh explored other aspects including benefits of inoculation and didn’t see significant yield benefits so far; COVID-19 prevented them from testing as many locations as intended last season. This research will continue in 2021, along with new studies looking at planting methods, seed priming and fertility under early planting.

Singh’s research shows that finding the right combination of planting date, maturity group and seeding rate could improve soybean yield. And this combination will need to be modified with each planting season due to weather and field conditions as well as costs of seed and other inputs. For farmers to improve their bottom line, thinking about yield potential is nonstop.

Resources:

Optimizing Soybean Planting Decisions for Maximum Yield/Profit presentation: https://www.canr.msu.edu/agronomy/uploads/files/2021_Soy%20management%20for%20high%20yield%20n%20profit.pdf

Michigan State University Extension Soybean Research webpage:  https://www.canr.msu.edu/agronomy/Extension/soybean

To find research related to this Research Highlight, please visit the National Soybean Checkoff Research Database.