Controlling Yield-Limiting Factors for Wisconsin Soybean Yields April 23rd, 2014

Date: April 23, 2014
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Linda Funk
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Controlling Yield-Limiting Factors for Wisconsin Soybean Yields

Linda Funk, Executive Director of The Soyfoods Council,


Controlling Yield-Limiting Factors for Wisconsin Soybean Yields 

Madison, WI, April 2014 —Wisconsin soybean farmers face many unique challenges during the growing season, most notably the impact of the weather on planting, growing and harvest conditions. The variability in weather can play a major role in determining the level of soybean insect, weed and disease pressure. Making timely decisions during the crop season can be the key to maximizing yields.

“Farmers have many considerations that effect soybean yield including variety selection, planting date deciding to apply inputs such as potassium, calibrating their planters for maximum yield and managing for seedling and plant diseases, yield-robbing pests and seedling,” says Shawn Conley, Wisconsin State Soybean and Wheat Extension Specialist. “Timely decision-making can be the key to maximizing profit potential with these most yield-limiting challenges.”

He recommends that soybean farmers compare variety performance results from multiple sources including university and private results, locations and environments.

“One common mistake can be only looking at local data from your own farm, a neighbor’s farm or from county data,” Conley says. “Local data, while interesting, only provide a glimpse at how well that soybean variety performed last year in a narrow area. Comparing variety performance over many different environments and factors will offer farmers the best predictive ability for next year’s environment.”

Planting multiple soybean varieties to diversify plant genetics may be a good strategy in lowering risks of
yield loss due to stress factors. Conley recommends paying attention to maturity groups because later-maturity group soybeans often lead to increased yield; however, timeliness of harvest and frost must be considered.

Once a group of high-yielding soybean varieties has been selected, the next decision is choosing varieties that meet specific disease, insect and weed resistance/tolerance characteristics keeping specific fields in mind.

Planting date can be one of the most important and least expensive cultural considerations that impact soybean yield.

Research conducted at the University of Wisconsin’s Arlington Agricultural Research Station has shown an average yield loss of 0.4 bushels per acre per day when soybean planting has been delayed past the first week in May. Yield loss in delayed plantings can be attributed to decreased seed number per acre.

Delayed plantings of soybeans can partially compensate for reduced pod number per acre through increased seed size. Early soybean planting dates can lead to increased risk of seedling diseases, white mold, brown stem rot (BSR) and sudden death syndrome (SDS).

Row spacing can be a factor in yields as well. The yield response of soybeans in wide rows versus narrow can vary by zero to 18 percent. The amount of water and light drives yield.  On average, research shows a seven percent yield difference between wide (30 or more inches) and narrow (15 inches and less) rows.
There can be greater yield loss in wide rows (more than 30 inches) versus narrow (less than 15 inches) because of increased weed competition. Row spacing does not affect canopy penetration of foliar fungicides.
Narrow row spacing may increase incidence of white mold; however, genetics (disease tolerance) and environment play a much greater role in managing this disease than row spacing. Wheel tracks from ground-driven sprayers decrease grain yield in 7.5- and 15-inch-spaced rows when applied to R3 and R5 (reproductive stages) soybeans. The extent of yield loss can be based on sprayer boom width.
More topics for the soybean growing season are covered in the Wisconsin Soybean pocket guide available at  In addition, Conley provides regular updates on soybean information. Visit


The Wisconsin Soybean