Evergreen Problems Webinar will be on April 22 from 7-8:30 p.m. Please call Platte County Extension at 402-563-4901 to RSVP. They will send you the Zoom link and password. There is no fee.
Considering Carbon: opportunities and challenges webinar will be held April 21 at 11 a.m. CST. Info & registration here: https://nationalaglawcenter.org/webinars/climate21/. There is no fee.
Reminder: Household Hazardous Waste Collection April 24th for Seward (8 a.m.-Noon) and Butler (1:30-4:30 p.m.) counties.
Soybean germination and planting: When I first began Extension, research on early soybean planting was just beginning. At the time, I hadn’t thought about planting soybean at the same time as corn, or even before corn. Soybean genetics and seed treatment improvements have allowed for this. Our recommendation for increased yield is to aim for planting the last few weeks of April if conditions are right, use a seed treatment, and plant 1.75-2″ deep. It seems like each year during planting season, we experience 1) soil temps in the mid-40’s with solid soil conditions and on a warming trend and 2) the potential for cold snaps with cold rains/snow after planting. What should one do and what’s the time-frame for risk of chilling injury?
For soybean, and corn for that matter, I’m not as concerned about #1 if the soil is fit and proper seeding depth (2”) is maintained. For #2, if the soil conditions are right and there’s at least 24 hours before a cold snap, consider planting beans instead of corn. That’s because soybean imbibes (takes up) water more quickly than corn. Once that imbibitional period is completed, the risk of chilling injury also ends. The seed can then remain (in osmotic phase) at cooler soil temperatures for a period of time in a sort of ‘dormant state’, until warmer temperatures return for continued seedling development.
In March 2021, Dr. Jim Specht and I began indoor and outdoor demonstrations. To be clear, we’re not recommending planting soybean in March in Nebraska. And, the point of these studies wasn’t to encourage increasing risk of pushing planting prior to cold snaps. I’m grateful for conditions like this year that make the decision to not plant easy when we know it’s staying cold with precipitation in the forecast. Our demonstrations just provided time looking at windows of 40-50F soil temps and increasing/decreasing trends. Soybeans are just beginning emergence from the March 10 planting in York. Soil temps in soybean and corn residue and living rye cover crop have been monitored since then and can be seen in an article at cropwatch.unl.edu. The soil under rye cover was 1-5 degrees cooler than under corn residue which was 1-2 degrees cooler than under soy residue.
We used coolers at 60F and 36F at the York Co. Fairgrounds to conduct an indoor experiment, explained in more detail at cropwatch.unl.edu. Enough trays were planted with soybean and corn seed so they could be switched between the coolers every 2 and then 12 hours for a total of two days. We didn’t have space for replications. All trays were removed to my house after 72 hours. They were kept at 50F for 9 days (which in many cases, early planted soybean do set in the soil for a period of time before emergence). Then they were kept at 60F soil temp with emergence counted each day until termination April 8. In the soybean, similar percent emergence was found in the 60F control; and where soybeans were at 60F for 8, 10, 12 and 48 hours before switching to 36F. This showed that we no longer saw reduced emergence upon 8 hours prior to a cold snap (in this non-replicated experiment). This potential 8 hour critical period has been within the time-frame of published research studies and non-published field observations.
The 36F to 60F switch showed that a warming trend in the first 2-6 hours led to greater emergence. We don’t recommend planting into soils at 36F, but it served as a nice low extreme. We would anticipate the emergence would improve if the soil temp was 40F or mid-40’s with a warming trend.
What does this mean? If soil conditions are right for planting and seed is planted around 2” deep with a seed treatment, I’m not as concerned about planting soybean or corn at 45F soil into a warming trend. For planting prior to cold snaps, if one chooses to do this, we say aim for at least 24 hours for soybeans and 48 hours for corn. We know not every soybean field is completely planted at 24 hours prior to a cold snap, so to me, this gives some insight why we’ve seen fields, including two on-farm research ones in Seward county last year, still have 86% emergence prior to snow falling eight hours later. Also key is when the beans will emerge compared to frost potential. If the beans are in the ground or have cotyledons exposed, we haven’t observed a need to replant due to frost damage thus far. It’s when the hypocotyl hook is at the soil line that can result in replant potential. Thanks to York Co. Ag Society for use of their coolers, Jerry Stahr for use of his field, Jed Erickson for providing the corn and soybean seed, and Dr. Jim Specht for his help in spite of being retired!