Beautiful planting conditions followed by serious cold and snow last May gave Ontario agronomists a living experiment in what happens when crops are planted into cold conditions.
How did the early planters fare?
It depends. As well, the story is different depending if you’re talking about early planted corn or soybeans.
Why it matters: Farmers are constantly pushing earlier planting in a bid to get more yield.
Three agronomists talked about their experiences with early planting at the recent Ontario Agricultural Conference.
Chuck Belanger, a market development agronomist with Maizex talked about planting early into clay in the southwest of Ontario, Deb Campbell, owner of Agronomy Advantaged discussed central Ontario and Chris Olbach, an area agronomist with Pioneer covers eastern Ontario.
Belanger focused on the need to take soil type into account when deciding whether or not to plant early.
“I’m not against planting early, I just think we have to be careful on some of the soils when we plant early,” he said.
How cold is cold?
It’s not just soil temperature that needs to be checked, he said, but also the weather forecast after planting. It might be 10 C at 4 p.m. on the day the field is planted, but how cold will that soil be over the next couple of days? Will the cold persist for the next seven days? A soil temperature of 10 C is considered the minimum needed for planting corn and soybeans.
Belanger implanted soil temperature probes at two locations last year, in Essex County and near Stayner. He found up to a 14 C fluctuation in soil temperature in one day.
Olbach also used soil temperature probes installed at planting depth of two inches to monitor soil during the early May cold snap. A field was planted on the evening of May 5 and the soil was well above 10 C. However, between May 8 and 10 it got to -3 C, with snow.
Seeds can double their weight in the 30 minutes after exposure to moisture, he said, and if that water is cold, that means stress for the seed.
Olbach found that the soil temperature fluctuated much less at two and three inches than it did at an inch, so measuring at soil planting depth is important.
He took the test of cold water imbibition to another level, hauling ice to a field at planting in an attempt to lower soil temperature and test the stress tolerance of a hybrid, which was supposed to be more tolerant. The soil temperature was lowered for eight hours and it reduced stand counts to 85 per cent of planted seed, but final yield showed little difference.
Belanger, Olbach and Campbell all emphasized the need to consider hybrid or variety before planting in colder conditions.
Belanger had a concrete example around the early May cold snap from 2020. A trial collaborator planted a clay loam corn field on May 8. That field got 2.5 inches of snow shortly after and then 2.9 inches of rain from May 15 to 17. A second field next door with a different co-operator wasn’t planted until after the May cold snap.
By July 24, a big difference could be seen between the two fields, with the early planted field looking much less healthy. That showed in final yield with the early planted field yielding 183 bushels per acre and the later-planted field 235 bushels per acre.
That’s not surprising as stand counts for the early field were 23,500 emerged plants from 36,000 planted seeds and 32,800 emerged plants from 34,000 planted seeds in the second field. Replanting of the early field was discussed, but didn’t happen.
In Campbell’s area, the cold weather meant severe chill for the seeds. Air temperatures got to -10 C in early May and frost reached two inches into the soil. Growers in her area of central Ontario are more worried about getting corn planted early enough to reach maturity before the first fall frost than they are about a June frost, she said, and as a result they will push early planting.
Seed that gets cold will stay in the ground a long time before germination. That makes seed treatments important for early planting, she said.
Also, pay attention to refugia seeds — the ones that contain non-traited seed in order to limit the development of resistance. Are those seeds going to germinate as well as the rest of the seeds that we planted? Campbell asked. Take a look to check.
Changing ideas on soybeans and early planting
Campbell said there needs to be more focus on soybeans and cold planting, as she saw some successes from farmers that planted soybeans into great soil conditions in a good field, before the early May cold snap. One farmer planted May 8, the night before a significant snow and still ended up with a yield of 83 bushels per acre on his “snow beans”.
If planted early, soybeans can avoid summer moisture stress at pod fill.
“If you can get to the first of July with five or six nodes on that plant and if it flowers in the first week of July in Ontario, that’s a sweet place to be and puts you in a high-yield scenario.”
Campbell said that there’s been data to support cooler condition soybean planting for 15 years and “That’s 15 years of solid data telling us repeatedly to plant soybeans early.”
Remember before planting in cooler conditions:
- Cold water soon after planting will set back seeds and yields.
- Watch the forecast 48 hours or more after planting.
- Choose well-drained, loamier soils.
- Choose a hybrid with more stress tolerance.
- Use full seed treatments.