Soil moisture for the state of Iowa remains below average as the winter freeze draws closer. Iowa State Climatologist Harry Hillaker explained that, statewide, Iowa saw just half as much rain as usual for November.
The unusually dry November followed an October with rainfall totaling a statewide average of 3.12 inches, half an inch more than the typical October average.
Denison, Iowa, reported 4.3 inches of rain from Sept. 1 to Dec. 4, about two-thirds the usual amount for that time period.
Unfortunately, Hillaker said that soil moisture remains well below the desired amount, especially in the northwest corner of the state.
“Things are worse north of Denison. They had a much drier fall up that way. Some places have maybe 3 inches of moisture, which is very little,” Hillaker said.
“They are already the driest part of the state and usually see less rain in the spring.”
In fact, as of Nov. 25, 81 percent of the subsoil and 57 percent of the topsoil were listed as “very short” in total moisture. Just 4 percent of subsoil and 14 percent of topsoil were listed as having adequate levels.
Soil in the west-central portion of the state is slightly better off, but still dry. Just 17 percent of topsoil and 1 percent of subsoil registered adequate levels of moisture.
For Denison, Hillaker estimated the soil moisture is, at best, 40 percent of the normal level for this time of year.
“Moisture levels remain low. The rain we did get fell on soils that were more depleted than usual at this time,” Hillaker stated.
As the frost nears, the opportunities for permeating rainfall are diminishing.
“Most areas are still short on moisture, which means there are not great consequences on the horizon,” Hillaker said. “Before too long, we anticipate soils to be frozen, and there won't be too much soil moisture recharge until they thaw out.”
Hillaker said that the low soil moistures were critical heading into the winter months because the average amount of rainfall for March and April would not be enough to fully recharge moisture levels.
“If we get normal rainfall in the spring, it still would not get us to capacity,” Hillaker stated. “Soil can hold 10 to 12 inches of precipitation. Assuming we receive normal precipitation, we still would be a bit on the short side.” He added that, typically, only about half of March's rainfall penetrates the soil.
Although the eastern portion of the state reports better soil levels than the west, soil moisture is still below desired amounts heading into winter. However, the prospect of good soil levels for the east remains a possibility after the thaw.
Hillaker said that soil is not the only aspect of agriculture lacking moisture as winter nears. Farm ponds and aquifers also have below-average levels of moisture and may stay as such into next year.
“Ponds and shallow aquifers have even worse prospects of getting back to normal. Soil needs to get saturated to see an increase of ground level moisture,” Hillaker said. “Farm ponds could be recharged, but it likely won't happen soon, maybe late next spring.”
While low water supply may be an issue next season, Hillaker said a long freeze and heavy snowfall could potentially benefit livestock producers more than crop growers.
“As far as pond levels and rivers, we would rather have ground frozen for more water to run off,” Hillaker said. But he added, “it would be more beneficial to have a frost-free season. We did get a benefit last winter from having the mild season by getting more moisture in the ground. But a deep snow cover would also help insulate the ground and keep it from freezing.”
Hillaker said that while a period of minimal frost would be ideal, any moisture would suffice.
“Right now, we will take whatever moisture we can get.”