
South Carolina farmers who are considering double-cropping soybeans behind corn need to remember the practice presents both risks and rewards, and offers different returns in different years, depending on the weather.
To increase their profitability per acre, South Carolina farmers over the last 10 years have increased their acreage of double-crop corn and soybeans. In 2020, there were less than 5,000 acres of double-crop corn and soybeans in the state. That number climbed to 20,000 acres in 2023, with a slight drop in 2024.
Clemson University is developing best management practices to help South Carolina farmers decide if the practice will work for them.
Bennett Harrelson, a doctoral student working on the project, said the goal is making the system as least risky as possible and ensuring farmers can make a realistic soybean crop following corn.
“From a profitability-per-acre standpoint, there’s not many things that historical grain growers can do on their farm to increase their profitability per acre compared to a monocrop corn or monocrop soybean system,” Harrelson said at the South Carolina Corn and Soybean Growers meeting Dec. 17 at the Santee Conference Center in Santee.
“Corn really needs to be planted in March. If you waited until April, the risks become too great in this system to be able to give these soybeans a realistic shot. We have to harvest corn at high moisture,” he said. “Growers are typically stating out at 25% moisture content and working their way through as the corn dries down to about 15½% moisture content.”
Factors for soybeans
Harrelson offered some factors farmers should consider when double-cropping soybeans:
Planting window. Soybeans should be planted in July through Aug. 7, with indeterminate Group 5 soybeans performing best in the system.
“There is a challenge to planting these soybeans so late. You have to have a dryer to dry the grain to get it out of the field. You have to have irrigation to push those soybeans late in the year,” Harrelson said.
Plant height. Soybean plant height in the system is critical. The goal is to have tall and rank soybeans that can easily move through the combine at harvest.
Crop insurance. Harrelson said because the soybeans are planted so late, there is no insurance on the beans.
Nematode management. Using nematicides in both corn and soybeans, and planting a nematode-resistant soybean variety is a must, Harrelson said. He noted the “Cadillac treatment” in their research of using Ag Logic and Counter 20G, along with a nematode-resistant soybean variety, did a good job of controlling nematodes.
In the podcast Science for Success, Harrelson said residue management is a big challenge in planting soybeans following a corn crop.
Farmers need to work through all the corn residue to ensure they achieve a good soybean stand.
In their research at the Edisto Research Center in Blackville, S.C., Harrelson and his team evaluated strip-tilling the soybeans behind the corn, offsetting the rows and then planting the soybeans directly into the strip till path.
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