Iowa farmers should let their drought-ravaged soil rest this fall, according to state and federal agronomists.
“It’s in their best interest to forgo fall tillage and fall nitrogen applications,” Jason Johnson, a public affairs specialist with the Natural Resources Conservation Service in Des Moines, said Wednesday.
Fall tillage will only dry out topsoil even more and expose it to the potential for extreme wind and water erosion, said Decorah farmer Paul Johnson, who formerly headed the NRCS and the Iowa Department of Natural Resources.
“This is a big deal. I’m really concerned. We need to let the soil rest for a few months,” Paul Johnson said.
“We all remember the black ditches that used to be common in the winter when we did a lot of fall plowing. We need to be careful this year,” he said.
Jim Fawcett, an Iowa State University Extension field agronomist in Iowa City, said, “With the harvest wrapping up early, it’s very tempting for farmers to roll right into fall tillage.”
As of Tuesday, 76 percent of the state’s corn had been harvested, a full month ahead of the average pace, and soybeans, with 80 percent harvested, were two weeks ahead of normal.
“This is not a normal year, and farmers need to resist the fall tillage temptation,” Jason Johnson said.
Resting the soil will allow earthworms and microorganisms to improve the tilth and fertility of the soil, and leaving the maximum amount of crop residue on the soil will preserve moisture and protect the soil from erosion, he said.
“We are advising farmers to think long and hard before they do fall tillage,” said Virgil Schmitt, the ISU Extension field agronomist in Muscatine.
Schmitt said the main justifications for fall tillage — to break up compacted soil and increase water infiltration — are not valid this year because of the drought.
“Mother Nature has already taken care of that for us with the deep cracks and fracturing associated with the drought,” Fawcett said.
“This is a year in which fall tillage could hurt water infiltration rather than help it,” Schmitt said.
Fall application of anhydrous ammonia and manure, two of the main corn fertilizers in Iowa, could also be counterproductive this year, Jason Johnson said.
Because of the drought, this year’s crops did not use all the applied nitrogen, he said.
“Disturbing the soil will just help it escape. You’ll be better off leaving it alone until spring,” he said.