5 Soil Facts
Jethro Tull isn’t just a 1960s and 1970s rock band. An English agriculturalist by the same name lived in the 1600s and 1700s. He loved to till the soil. And till. And till some more.
“He believed the more you tilled, the better the soil,” says Aaron Daigh, a North Dakota State University (NDSU) soil scientist. Tull reasoned that the tiny soil particles caused by tillage pulverizing the soil would be easier for plants to suck up as they grew.
Fortunately, farmers and soil scientists have come a long way since those days in understanding soils. Still, there are some soil facts that often fly under the radar. Here are a few to keep in mind from Daigh and Jodi DeJong-Hughes, University of Minnesota (U of M) Extension crops educator.
1. Rocky soils are a pain. But it could be worse.
Farmers in states like Minnesota and the Dakotas may cuss the rocks that glaciers deposited thousands of years ago. On the plus side, these glaciers also helped create some of the best soils in the world.
“Up here, it is amazing how black and deep the soils are,” Daigh says. He compared that with the bright red soil of western Arkansas (where he grew up) that had just 1 to 2 inches of topsoil.
2. There’s a downside, though, to farming deep and rich soils.
“You can abuse these soils, but you won’t be able to see the effects right away,” says DeJong-Hughes. One way to check whether soils are being battered is to fly over them during the growing season.
“If the crop is doing better in the wheel tracks of the tractor and planter, you are doing too much tillage,” she says. “It’s making the rest of the soil in the field fluffy. She’s coined the term fluffy soil syndrome for this scenario.
3. Hazy day? Blame the clay.
Ever notice how windy days often have a hazy hue to them?
That effect is due to the clay particles that have become detached from the soil, says DeJong-Hughes. These particles travel far. Some particles have traveled from Minnesota and North Dakota to as far east as New York City, she says.
Meanwhile, detached sand and silt particles gravitate to ditches.
4. Well-structured soils are chock-full of benefits.
“Roots move through them quickly,” says DeJong Hughes. “They like the path of least resistance.”
Meanwhile, soils with excellent soil structure contain plentiful pores that promote excellent water and gas exchanges.
So how do you build soil structure? “Cover crops help,” DeJong-Hughes says. “So do more intense crop rotations. Adding manure is fantastic for the soil.”
5. Unfortunately, tillage will break down soil structure with whatever form of tillage you choose.
This even includes the slight tillage used in no-till to make way for the seed. So what do you do? After all, you still need to farm.
One way you can prevent tillage from worsening soil structure is by staying off fields when they are wet. Field operations performed on excessively wet soils can have decade-long soil structure consequences.
DeJong-Hughes and Daigh cite a 1981 trial in Finland where a tractor-trailer combo drove over excessively wet plot areas. Twenty-nine years later, Nordic researchers performed a computerized topography (CT) scan of soil samples pulled at a 0.9 to 1.2 foot depth. CT scans were compared with a control soil that dried before field traffic passed over it.
After nearly three decades later, the soil structure of the areas through which the tractor-trailer drove was still damaged. The researchers noted the damage would have been worse today, as equipment is larger.
Realistically, farmers are sometimes backed into a corner during wet falls. They face a tough choice between harvesting on wet soils or letting corn linger over winter. Fortunately, Upper Midwest farmers have a soil compaction buster better than any deep ripper.
“Around here, there are extreme winter lows and summer highs, the biggest spread in continental North America,” says Daigh. “When our soils crack when it is dry, it can easily go 8 to 9 feet below the ground. That is the best form of deep tillage.”
Watch Spring Soil Temperatures
Soil temperatures are a huge factor in determining what to do when rain, snow, and bone-chilling temperatures sweep across your fields.
Jay Zielske, an account manager for DuPont Pioneer in southern Minnesota, noted in a newsletter last year to customers that cold weather brings with it concerns about imbibitional chilling injury. Damage from the seed imbibing cold water runs the gamut – from seed death to maladies like corkscrews or fused coleoptiles.
“It definitely is a phenomenon that can occur,” he says. “However, its occurrence isn’t always predictable, as numerous factors come into play.”
The magic number when it comes to imbibitional water uptake is 50°F., note University of Nebraska (U of N) agronomists and Extension educators.
Once planted, corn seeds need a 48-hour window when the soil temperature at planting depth does not drop much below 50°F. Below 50°F., potential exists for chilling injury to affect seed germination and seedling growth. Soil temperature decreases after this time are less likely to affect seed germination.
The U of N scientists note that debate exists about what specific temperature and timing cause imbibitional chilling. If temperatures dip down to the low 40s in the first 48 hours after planting, seed chilling risk is high. Some scientists suggest that corn will not be injured at soil temperatures as low as 41°F. However, injury risk from imbibitional chilling at those low temperatures still exists.
Soil Health Helps Feed the World
Talk to any agricultural company, and you’ll hear that its products are needed to feed a growing global population estimated to hit 9.7 billion by 2050. Still, products alone won’t be able to do it. Improving soil health will also be necessary, says Annie Dee, president of Dee River Ranch in Aliceville, Alabama.
“My dad bought property in Florida in the 1950s, and when I got out of college, I went to work on that farm,” she says. “In the late 1980s, I moved to Alabama. I started farming in sandy soils (in Florida) and then farmed heavy soils in Alabama. Some of the greatest opportunities I’ve had are to improve soil health, to build organic matter, and to improve the CEC (cation exchange capacity) of soils. Improving the soil is a real way to feed 9.7 billion people by 2050.”