Untreated Soybeans Face Uphill Battle To Emerge Unscathed by Cold Soil Conditions
If you have an itch to plant untreated soybean seed in cool soils this week, let this truth change your mind. The longer seeds sit in cold dirt unable to fire a plant and emerge from the soil, the higher your risk that sudden death syndrome (SDS) will snuff out a chunk of your soybean yield potential later in the season, says Ken Ferrie, Farm Journal Field Agronomist.
“The beans planted last week here in central Illinois may take three weeks to get out of the ground, based on the weather forecasts, and that could be concerning,” he reports.
In scenarios where the seed just sits in the ground, the risk for SDS to develop trends higher. The disease can quickly decimate any early planting yield boost you might have anticipated capturing.
“While the gain from early planting can be five to 10 bushel per acre, we've seen SDS turn an 80-bushel soybean crop into a 40-bushel crop in a hurry,” says Ferrie in this week’s Boots In The Field agronomic podcast.
Furthermore, if your crop is infected by SDS, you likely won’t even be able to confirm it until weeks from now.
What happens is the fungus Fusarium virguliforme infects soybeans in their early growth stages, but the foliar symptoms won’t appear until it’s too late to protect against the disease. Growers can experience as much as 80% yield loss from SDS, according to Douglas Jardine, Extension plant pathologist and professor emeritus, Kansas State University.
The Impact of Seed Chilling
Farmers in areas that have soil temperatures below 50 degrees Fahrenheit also need to be leery of seed chilling issues if they choose to plant corn during an unfavorable weather outlook.
The issue is when seed corn takes on water and swells in that first 48 hours after being planted, the temperature of the soil moisture (water) is important. Water temperatures above 50 degrees give the seed cells elasticity, allowing them to stretch as they take on water, Ferrie explains. When water temperatures are below 50 degrees, the cells lack this elasticity and instead of swelling the cells tear.
“This is what we call seed chilling, and the signs of seed chilling can show up in different ways,” he says. “Sometimes the seed doesn't fire at all. Sometimes it'll throw a root but no shoots. Sometimes it'll throw a shoot but no roots.”
He says the most common form of seed chilling farmers see is corkscrewing that occurs at the mesocotyl, which can prevent the plant spike from reaching the surface.
Seed chilling can eliminate 7% to 10% of the corn stand in a field. In addition, late-emerging spike down plants can account for another 7% to 10% of the stand.
Once soil temperatures get above 50 degrees Fahrenheit, the problem of seed chilling dissipates quickly.
“Once the seed has swelled and germination fires, seed chilling is no longer much of an issue,” Ferrie says. “Even if temperatures drop into the 40s all that will happen is the plant is going to be slower to emerge.”
However, he adds, the longer corn seed and plants spend below the ground surface the higher the risk for loss to occur from seedling diseases and insect damage.
Reports of Low Germination Scores
Ferrie reports he is getting calls from farmers about entire lots of seed – both corn and soybeans – that have been discarded due to germination issues.
He says these two questions have come in from more than one grower: “If I'm going to push planting conditions with marginal seed quality, should I increase the population? Or, should I plant the ones with more ear flex?”
Ferrie’s response: “That's kind of like asking, ‘if I'm gonna shoot myself in the foot, should I shoot the big toe or the little toe?’ There is no good answer. I know we're showing some pretty amazing yields in our fixed-flex plots where we're seeing well over 200-bushel yields with corn planted at 22,000 population. But remember, these are picket fence stands planted at 22,000 where each plant gets equal sunlight. Don't expect the same results when you're planting 36,000 to get an ear count of 24,000.”
Going back to the original question about which toe to shoot off, Ferrie says that bumping up the population a little and using a more flex hybrid may make it a little less painful.
On the soybean seed side where there are lower germ scores, Ferrie says he would bump up populations. “Guys are bumping these 80% germs by 10% to bring those counts back up,” he reports.
You can get Ferrie’s complete agronomic recommendations on dealing with lower germination scores and getting crops off to a strong start this season here: Corn and Soybean Planting Now Underway in 16 States
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