Iowa Soil Temperatures Available Online To Help Make Planting Decisions

Iowa Soil Temperatures Available Online To Help Make Planting Decisions

It's tempting to get into fields as soon as top 3 inches are suitable, but consider what's happening further down in soil profile.

Iowa State University Extension agronomists are concerned that the air temperature is warming up but farmers will jump the gun and start fieldwork and planting corn before soils are ready. If you get into fields too early on wet soils, you risk causing soil compaction problems that could create issues with root systems later on.

PATIENCE PAYS OFF: Patience is a scarce commodity at planting time. But don't get into fields before the ground is ready. If heavy equipment is pressing down against frozen ground down in the soil profile, the soil compaction problem is aggravated.

"It's tempting to get out there as soon as the top few inches of soil are ready, but you need to consider what's happening further down in the soil profile," says Mark Johnson, an ISU Extension field agronomist in central Iowa. "If heavy equipment is pressing down against frozen ground below, soil compaction will be enhanced in the area between the upper worked area and the hard frozen area. This spring, working the ground as little as possible will most likely pay dividends."

Another question he's getting from farmers concerns when to terminate cover crops prior to planting corn and soybeans this spring. "If you have cover crops on your land, be sure to work on terminating the acres going to corn first," says Johnson. "Killing a cover crop at least 10 days ahead of corn planting is best. Termination ahead of soybean planting is not as necessary. In fact, you can terminate all the way up to and including preemergence of the beans without concern for yield penalty."

 Patience is a scarce commodity at planting time
"You should plant corn after soil temperatures have risen above 50 degrees F and weather forecasts ensure that warm weather continues," advises Mark Licht, another ISU Extension field agronomist. "Remember to stay patient when it comes to planting so you can avoid the planting mistakes that would haunt your crop throughout the growing season."


Soil temperatures for each county in Iowa are available at Iowa State Mesonet and Ag Weather facts along with other weather information. That includes soil moisture readings for the network locations in Iowa that have the new weather stations installed. Those stations have sensors which measure moisture content in the top 5 feet of soil.

Early planting date for crop insurance replant coverage
Keep in mind the crop insurance "early planting date" to qualify your corn for replant coverage. That's April 11 for Iowa, says Kevin Erickson, crop insurance specialist with USDA's Risk Management Agency at the St. Paul regional RMA office, which covers Iowa, Minnesota and Wisconsin.

If you plant corn in Iowa on April 11 or thereafter, you'll qualify for replant coverage if you have crop insurance. However, if you plant corn earlier than April 11 and end up having to replant the crop later, you'll have to pay for the replanting yourself, says Erickson. Your corn crop will be covered by crop insurance for other indemnity claims that you have coverage on, but you will not receive payment for replanting, if your original planting date is earlier than April 11.

For soybeans, the early planting date for crop insurance purposes is April 21, says Erickson. If you are in Iowa and plant beans earlier than April 21, you will not be covered by the replant provision of crop insurance.

Can rain soak in if frost is still deeper in soil profile?
This past winter was so cold that frost formed as deep as 6 or 7 feet in the ground in some areas of Iowa. Rain in early spring will help take some of the frost out but the rain likely won't contribute much, if any, to soil moisture replenishment, says Licht. Spring rains, like spring snowmelt, doesn't add much to soil moisture reserves because the frost prohibits downward infiltration. In fact, while early spring rains can help take out frost, it often leads to tremendous amounts of surface water runoff and soil erosion. The best case scenario is to get the frost out with warmer weather and then get some moderate rains to replenish the soil moisture profile.


In northwest Iowa, soil has thawed a little during the past week, says Paul Kassel, ISU Extension field agronomist at Spencer. Frozen soils in some areas are extending into spring, and farmers are concerned cool soil may limit early season root growth. "The solution for frozen soil down in the soil profile is a week of warm rain. I'm not sure how we order warm rain instead of cool rain, but I'm optimistic warm spring temperatures will also help thaw the soil out," he says.

Much of Iowa still needs soil moisture recharge
One thing the very cold winter didn't do was break the drought. Much of Iowa still needs a recharge of reserve subsoil moisture, says Clarke McGrath, ISU Extension field agronomist at Harlan in western Iowa.

Taking a look at the drought monitor website you can see that most of Iowa currently ranges from abnormally dry to a few areas of severe drought with a majority of the state in a moderate drought. "We often catch up in the spring, as rain recharges soil moisture supplies, but that brings on another set of challenges," says McGrath. "No matter what this spring's weather will challenge us with, Iowa's farmers and retailers always get the job done and done well on the vast majority of our acres. Be safe this spring and don't get in too big of a hurry."

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