Plant when soil conditions dictate, not calendar

BLOOMINGTON, Ill. — Planting soybeans earlier than what was the norm back in the day is another way to drive yield, but don’t overlook soil conditions and the forecast.

The goal of early planting is to increase yield by getting soybeans to flower early and extend the reproductive growth period, leading to more and bigger seeds in the pods.

Kelly Robertson, soil fertility agronomist, precision agriculture consultant, owner of Precision Crop Services in Benton, and ILSoy Advisor Soy Envoy, stressed the importance of looking at soil conditions first.

“The reason we like to see soybeans planted early is because they yield more, but one of the things that we do that can cut that yield is to plant them into less-than-ideal conditions,” Robertson said in an ILSoy Advisor presentation.

“There’s kind of an urban legend or myth that soybeans could be planted wetter or into conditions less suitable than corn can and still get maximum yield.

“We penalize ourselves when we plant into those conditions because we do the same things that we do in corn. We cause some sidewall compaction. We don’t get the seed slot closed, and what not.”

A field may look dry and ready for planting. Use a shovel to check the soil, and if the soil is shiny, it’s not fit to plant.

“Just like with corn, when we plant soybean too wet, even with spike closing wheels and other attachments to try to get the furrow closed, the seed trench can open up as the soil dries out exposing the seeds,” Robertson said.

“The other thing we do is maybe we’re a day or two early, we’ve got enough pressure from the spike closing wheels and the downforce on our planter to get the slot closed, but we’re mashing those beans in against the sidewall.

“Sometimes we want to apply too much pressure to close the seed slot when it’s wet and we end up burying the soybeans, and the soybeans try to leaf out underground. That’s not a good situation to be in.”

Planter Adjustments

It’s not unusual for planting conditions to vary across one field. The planter should be adjusted accordingly.

“The other thing we do is we set the planter in the best part of the field where we start and then as we go through the field we get into other conditions. We run into situations where maybe one row was planting real good and the other wasn’t,” Robertson said.

“We need to make sure we’re constantly adjusting our planter due to situations in the field. Remember, success with soybean planting is just like with corn. Plant when the soil conditions dictate it, not when the calendar does, for best results.”

Freeze

One risk for planting early is freeze damage. The median last frost date in Illinois ranges from late April in northern counties to early April in the south.

“Hard freeze medium dates run a week or two earlier depending on the county. Illinois experienced a late hard freeze the week of April 24, 2023. Areas as far south as I-72 observed hard freezes that morning with some young crops seeing injury,” Matt Reardon, Nutrien Ag Solutions senior atmospheric scientist, wrote in his recent ILSoyAdvisor post.

Steve Cromley, Pioneer field agronomist, said corn and soybeans were up and growing when the late April freeze hit his territory in central Missouri last year.

“The growing point of corn is below ground until about V6 growth stage. The growing point on a soybean plant is above ground at emergence and more susceptible to freeze damage at that point,” Cromley said.

“The soybean plant is also susceptible to freeze damage during emergence as that hypocotyl is emerging from the soil.”

Last year’s late freeze reaffirmed for Cromley that residue does affect temperature at the soil surface.

“Residue reduces the transfer of heat from the soil to the plants, resulting in cooler temperatures near the surface,” Cromley said.

“In multiple fields that had areas that were tilled and areas of no-till, the no-till areas were worse than in areas that had been tilled with no or very little surface residue.

“The no-till areas had to be replanted while the tilled areas had sufficient populations for maximum yield.”

Field Selection

For those planting early, Cromley recommended planting soybeans first in fields with very little or no residue.

“Also, avoid starting first in creek or river bottom fields. Low-lying areas are more susceptible to freeze damage and that was evident in 2023,” he said.

“I do not recommend planting shallow to encourage faster emergence, because once that plant starts to emerge, it is at risk of freeze damage. So, use a seed treatment and plant at normal depth.”

Other early planting recommendations include choose a variety with good resistance to sudden death syndrome; consider planting 10% to 20% more seeds per acre if conditions are conducive for seedling mortality. Only plant if favorable weather is forecast.

“The seed will imbibe moisture if available within 24 hours. Chilling injury can occur and lead to reduced stands if the seed imbibes cold water,” Cromley said.

“Soil temperatures should be above 50 degrees and predicted to stay above those levels before planting.

“One question I have gotten is should I plant soybeans before corn. Corn has a shorter optimal planting window compared to soybeans, and the yield penalty for planting corn late is greater than for soybeans. So, don’t delay your corn planting to get the soybeans in the ground.”