Yields Squeezed By Soil Compaction

ANKENY, Iowa (DTN) -- Deep tillage isn't necessarily the answer to alleviate soil compaction and prevent subsequent yield loss. In fact, the once go-to fix may do more harm than good.

Aaron Daigh, a North Dakota State University assistant professor of soil physics, recommends farmers leave chisel plows and disk rippers in the shed this spring to save time and money and to prevent more potential problems. If there are already ruts from heavy equipment traversing wet fields during harvest, which is still ongoing in the Upper Midwest, the damage is most likely already done, he said.

Farmers can expect crops to yield 20% less, on average, for the next two years in areas where ruts are visible, according to Daigh. Compaction prevents proper root growth, water infiltration and water availability.

"It's been quite a year for ruts and compaction for sure, and there's plenty of evidence everywhere," Daigh said, referring to pictures on social media of buried combines, tractors and grain carts. "There's still compaction happening with winter harvest."

Many farmers believe deep tillage is the way to alleviate compaction, Daigh said. For it to possibly work, Daigh added, subsoil needs to be dry and shanks of the primary tillage tool need to get at least 2 inches below the compacted area to lift and break up the ground. A penetrometer is needed to get accurate compaction depth readings.

The tool typically has a detailed color-coded gauge that shows farmers the resistance of the soil based on how much pressure is needed to break through it. Root penetration typically stops at 300 or more pounds per square inch, Daigh said.

"Without a measurement, farmers are just aiming in the dark," Daigh said. "What we see with deep ripping, it has a low success rate and you just burn time and diesel. Even if you try to rip it, there will still be a level of yield loss."

The soil expert urges farmers to wait until fields are fit to do any tillage. However, he understands farmers have tough decisions to make when weighing spring field work needs, the weather and soil conditions.

"As painful as it sounds, my advice is patience, patience, patience," he continued. "It's very tempting to go out and till to fix problems and get the ground to dry out faster. But if it's too wet to plant, it's too wet to till."

Tilling while it's wet will only "smear or slab-over" soil, which will prolong and enhance compaction problems and exacerbate future yield losses, Daigh said. "Just know compaction is bad and it has a lifespan."

He advises farmers to fill in ruts once fields are dry so fields are smooth for proper seed-to-soil contact while planting. Otherwise, farmers risk poor emergence and stand issues, which also contribute to yield loss. He recommends using secondary tillage implements like a field cultivator for cuts a few inches deep, hitting them at an angle and not digging underneath.

For deep ruts, a skid steer or an excavator may be needed to fill in holes, coupled with light tillage to smooth the surface.

GOOD ADVICE

Joe Morken of Casselton, North Dakota, plans to follow Daigh's advice. All equipment will stay in the shed until fields are totally dry, and that includes the combine, even though he still has about 1,000 acres of corn still standing. North Dakota has the most acres of unharvested corn at about 1.4 million, followed by Wisconsin at 988,000, according to the latest USDA reports.

Morken said combining soybeans last fall left enough ruts 3-4 inches deep.

"We'll wait to harvest and till until fields are dry so we don't do any more damage," he said.

Morken said he didn't notice a yield hit in 2019 despite shallow ruts left after the wet 2018 harvest because he waited until conditions were fit to commence fieldwork.

Once fields dry this spring, Morken plans to hit ruts with a field cultivator to fill them, apply inputs and plant corn. Then he'll combine the remaining 2019 crop, which is standing well except for some outside rows that collected more snow. After that, he'll plant soybeans if time allows.

"We're having an early snowmelt and fields are draining, so it may not be too bad," Morken said. "But we get a few 1- to 2-inch rains in late April and May; there will be a lot of PP (prevented planting) up here."

COMPACTION PREVENTION

The University of Wisconsin (UW) Extension established guidelines to avoid soil compaction:

-- Wait for better soil moisture conditions before conducting fieldwork, but that's not always possible.

-- Reduce axle loads, maintain low equipment tire pressure or use machinery with tracks if possible.

-- Manage equipment traffic patterns to contain and reduce soil damage.

-- Don't assume subsoiling is needed.

-- Surface tillage might be needed to address ruts.

-- Cover crops can help.

"Preventing soil compaction from happening is usually the best management approach," according to UW Extension.

Multiple freeze-and-thaw cycles will naturally alleviate soil compaction as will extreme dryness if deep soil cracks occur. Planting cover crops is also one of the better ways to prevent it, experts say.

Fibrous and tap roots from barley, wheat, tillage radishes and other plants work their way through compacted soil to break it up. Plus, cover crops enhance aggregate stability to better handle heavy equipment.

"Believe it or not, you don't have to rut up fields just because it's a wet fall," said Barry Fisher, USDA Natural Resources Conservation Service soil health specialist based in Indianapolis. "A system that builds better aggregate stability will prevent that."

Matthew Wilde can be reached at matt.wilde@dtn.com

Follow him on Twitter @progressivwilde

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