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Building soil for a changing climate

Jerry Hatfield of Ames, Iowa, speaks to farmers at field day
BOOSTING YIELDS: Jerry Hatfield, director of the National Laboratory for Agriculture and the Environment in Ames, Iowa, says three factors limit corn yields: high July temperatures during corn pollination, high nighttime temperatures during corn fill, and July and August rainfall.
How farmers manage soil can impact the health of the soil and crop yields.

The Upper Midwest is getting wetter over time, while the Southwest and Southeast are getting drier, according to Jerry Hatfield.

“We are getting more and more of our precipitation in intense storms, defined as 1.25 inches of rain or more per storm,” said Hatfield, director of the National Laboratory for Agriculture and the Environment in Ames, Iowa, on Aug. 3 in Dodge County, Wis. He spoke to about 250 farmers and agriculturists at the Healthy Soil-Healthy Water Farmers Alliance Field Day at the Hammer and Kavazanjian Farms near Beaver Dam.

Hatfield said intense storms cause problems with runoff and soil erosion. He also said the normal amount of precipitation is increasing.

“We have less dry years than we used to,” he noted. “Our weather is getting more variable. We are seeing more spring precipitation and less summer precipitation in Wisconsin and most of the Midwest, leading to wet springs and dry summers.”

Hatfield said the growing season in Wisconsin and across most of the Midwest is getting longer.

“Our frost-free season is getting longer,” he said. “We have nine more days of growing season in Wisconsin than we did 20 or 25 years ago.”

Getting wetter
The state is also seeing more hot nights — above 75 degrees F.

“Rising temperatures is not coming from higher maximum temperatures; it’s occurring because we are raising our nighttime temperatures,” he explained. “Nighttime temperatures above 75 degrees place a lot of stress on animals, humans and plants. This is especially critical during grain fill.”

Shifting precipitation patterns increases the potential for summer drought, Hatfield added. And short-term stress can affect yield.

“We need 2 inches of rain, and we only got 1 inch for the week — this can reduce yields,” he said. “If it doesn’t rain for three weeks in August, it can cost 40 bushels of yield loss in corn, because that corn had to rely on what moisture was stored in the soil.”

Hatfield said how farmers manage their soil can impact soil health and yields.

“We get compaction and crusting and water and wind erosion, and that leads to reduced plant growth and lower yields and reduced soil productivity,” he said, adding that soil needs air.

“If you have soil that is crusting and compacting, it’s a lot like a person having COPD. If you have COPD, you have a hard time breathing. So does soil that is crusted and compacted,” he explained.

Hatfield said there are three factors that limit corn yields:

• high July temperatures during corn pollination
• high nighttime temperatures during corn fill
• July and August rainfall

Take control with no-till
Hatfield is a big believer in no-till. “Conventional tillage continues to degrade the soil,” he said. “We can’t control the weather, but we can control our soils. We can rebuild soil, but it requires work. We have to restore the soil biological activity. You can’t till your way to good soil health.”

Hatfield also likes to have crops growing in crop residue.

“On hot days, the sun can cook the biology right out of the soil if there is no crop residue,” he said. “The soil can get up to 120 degrees on a hot day before the corn is tall enough to canopy and cover the soil.”

Hatfield said earthworms, insects and gophers are nature’s plows.

“When we improve the soil biology, we see less deficiencies in our crops, especially during the grain filling time,” he said.

A farmer’s job is to get rain into the soil, he said.

“The more you keep that plant unstressed, the more you increase your yields,” Hatfield said. “To offset more spring precipitation and more variable summer precipitation will require a soil system that can absorb heavy rainfall events and store moisture.”

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