RALEIGH, N.C. — We have had several questions in the past 24 hours about continuing to plant soybeans this week with cool weather on the horizon. If you want to get something done this week, planting soybeans is going to be a safer bet then planting cotton or transplanting tobacco.
The general consensus from colleagues in the Midwest is that we need sustained temperatures (>4 hours) at or below 28°F to kill emerging soybeans. A good summary of this information from the University of Wisconsin-Madison can be found here.
I talked to Dr. Shawn Conley, Soybean Specialist at the University of Wisconsin-Madison, last week and Shawn said that if soil temperatures are 45°F or above and no cool rain is in the forecast for the next couple days, they will recommend growers can get started planting soybeans. We are well above those soil temperatures across North Carolina, with average soil temperatures across the state currently in the low-to-mid 60’s.
What you do not want to do is plant in front of cool rain snap. Across most of the state there is limited rainfall, if any, forecasted for the next week.
Although unlikely this coming week, if you do see what you think might be freeze injury in your soybeans, here are some photos from Purdue University of what to look for. It is recommended that you wait for several days after the freeze injury occurs before you assess damage; this allows the soybeans an opportunity to recover before making decisions about replanting.
With temperatures cooler than normal, if you have the option to plant seed treated with a fungicide, our preliminary data suggest that would be merited.
–Rachel Vann, N.C. State University