Dry conditions during the fall and frigid temperatures this winter led to a deep freeze in Iowa’s soil.
Some farms are still experiencing frost more than three feet deep because cold air was able to travel through cracks in the soil from a dry finish to the 2013 harvest season.
But the deep freeze may provide some benefits for farmers if they can practice patience and wait for warmer temperatures to return before starting the 2014 planting season.
“This time of year our temperatures are extremely variable,” said State Climatologist Harry Hillaker. “It is characteristic of the season to go between both extremes (warm and cold temperatures).”
The frost helps fracture the soil, breaking up any compaction as it freezes and thaws with the spring temperature.
“For the most part, it is a good thing,” said Iowa State University Extension field agronomist Aaron Saeugling. “Frost is one of the best tools we have to break up soil compaction.”
Less compaction allows the soil to absorb water deeper into the subsoil and makes it easier on seeds as they germinate and break through the topsoil.
“Until that frost is gone, the topsoil is going to be extremely wet and saturated,” said Hillaker. “Any moisture has nowhere to go until the frost is out of the ground.”
Air, soil temperature
On average, this March is 10 degrees cooler than years past. Unlike 2013 when the temperatures were consistently low, this March started with record-low temperatures before quickly climbing to near-record highs less than a week later.
Hillaker said average temperatures for mid-March in southwest Iowa is typically in the upper 40s.
Besides temperature, the total amount of moisture for this March is below average, as well.
“It looks to stay that way,” Hillaker said. “It doesn’t look like any tremendous amount of moisture is expected across the area in the extended forecast.”
Saeugling said if the area did get a warm rain or high temperatures, the frost could leave the soil quickly.
“If we have a prolonged, slow warm up, obviously it is going to take longer to warm up the soil,” Saeugling said.
Wayde Ross, Natural Resources Conservation Service district conservationist for Union and Ringgold counties, said the area is still on the dry side according to drought monitor maps.
“What little runoff we are getting, it is running into the cracks (in the soil),” Ross said. “The ponds are still low.”
The soil in southwest Iowa is averaging in the low- to mid-30s. Optimal growth temperature of the soil for corn is above 50 degrees and soybeans are above 54 degrees.
At Iowa State’s research sites in Greenfield and Lewis, Saeugling said the temperature is 33 to 35 degrees about four feet below the surface.
Ross agreed that the frost will not delay when farmers should be in the field planting based on soil temperatures and initial plant dates for crop insurance.
The initial planting date for corn in Iowa is April 11. Soybeans are scheduled for April 21.
“Last year was rather difficult season to say the least,” Hillaker said. “It was dry enough to get into the field, but the soil was way too cold until the middle part of May. It was a frustrating season.”
While a majority of the timing for when farmers will get in the field is weather dependent, if farmers till or use no-till practices is also a factor for this growing season.
“If you do tillage, it turns the soil and warms it quicker,” Ross said. “When you don’t strip the soil, it works as an insulator.”
The delayed start to spring has stunted the growth of annual weeds. Ross said by not disturbing the soil, it does not stir in the weeds where they have a chance to germinate.
“Farmers will have a chance to address weed control,” Saeugling said. “We are still about 30 days out. The ground is still frozen pretty hard, but when they do get going, they are going to hit it hard and fast.”
