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Research Highlights

Research Highlights
Soybean planting date and tillage systems can affect variable rate seeding

By Carol Brown, USB database communications

Variable rate application for planting soybeans is a technology that can help farmers fine-tune their plant populations within a field. By varying seeding rates across a field, farmers can reduce seed costs.

Researchers in Michigan are taking this a step further by exploring if soybean planting dates and tillage systems can improve yield when combined with variable rate planting.

“When farmers are asked when they begin planting soybeans, many times the general answer is ‘after I finish planting corn’,” said Missy Bauer, lead project investigator and independent crop consultant.“We saw this as an opportunity for yield gain if they pushed soybean planting a little bit earlier. We also wanted to look at the effect of vertical tillage compared with no-till planting early.”

Bauer’s approach to variable rate planting is based on the idea that seeding rates should be increased in less productive zones in the field and decreased in highly productive zones. She wanted to determine if seeding population prescriptions should be changed based on planting date and/or tillage method.

Missy Bauer led an on-farm study that compared early and later planting dates of variable rate seeding in no-till and vertical tillage situations in 2017 and 2018.

To find the ideal combination, her team studied several scenarios at two locations on private farmland in south central Michigan over two growing seasons.

“By using actual farm fields, we’re trying to embrace the variability that’s actually in the field,” Bauer said. “Knowing there’s different soil types out there, we’re managing by those soil types and tracking yield by soil type and management zone.”

The field study included two planting dates, vertical tillage and no-till systems, and two variable rate planting prescriptions calculated to result in either a higher average plant population across the field or a lower average population. The best economical treatment across the research site locations was a combination of early planting with vertical tillage and lower seed population planting rates, according to her research report.

“Early planting date increased yields on average of 3 to 4.8 bushels per acre (bu/ac) over the two years. If we planted early, we were fine with the lower average population,” Bauer said. “The vertical tillage performed better than no-till in both early and later planting date situations.”

“With earlier planting dates, beans are bigger, and they have earlier canopy closure,” Bauer said. “If farmers get out there earlier, they can get by with average or lower populations. But if they get planting late, the theory is we should push populations to get canopy closure sooner.”

Bauer said seed population should be adjusted based on planting date by increasing numbers with later planting dates. If planting late, vertical tillage and higher populations were important and increased yields an average of 3.2 bu/ac, compared to no-till with lower populations.

Bauer owns B&M Crop Consulting with her husband, and they have worked on numerous projects with checkoff support from Michigan Soybean Promotion Committee, including studies on white mold, soybean cyst nematode and sudden death syndrome.

Case IH and Great Plains Ag provided in-kind support for this study.

Also, read the article in Farm Journal on this research.

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