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The truth about tillage

Tests show heavy tillage is your enemy by damaging water infiltration and soil health.

Think Different

“Why do we plow? To make the land like a sponge,” Lynn Boadwine remembers his dad and others telling him from the time he was a boy. Years later, the Baltic, South Dakota dairy farmer is seeing things differently. The results of a series of eye-opening, simple infiltration tests on his own land completed the turnaround in his thinking.

“The infiltration on the field that was manured, deep ripped and field cultivated was terrible,” he says. “I’m convinced now that heavy tillage is your enemy. I carry a spade with me now, and on the end rows I’ve tilled a lot, when I dig with that tile spade, I can see that the tillage harms soil structure more than it helps.”

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If it seems like common sense to you that tilling your land like a garden helps more rain water soak into the ground, you might consider trying a few simple infiltration tests to see for yourself whether tillage helps or hurts water infiltration.

That’s what Lynn Boadwine did last spring. In his part of the world, southeast South Dakota, he can’t depend on regular rains for a corn crop. “I don’t know a lot about water infiltration, but I know I’ve needed more water for my corn crop these past few years,” Boadwine says. “Corn silage is our best forage for dairy, but it doesn’t rain here every week and our corn fields can burn up quickly.”

Lynn Betts

 He’s tried cover crops with varying success. In his first experience several years ago with cereal rye he took a 25-bushel hit on corn yields and was disappointed. “So the next year I didn’t use cover crops. But we had runoff and soil erosion on land we chopped for silage,” he says, “so I went back to cover crops the next year. Besides the protection the cover crops gave the soil, I was pleasantly surprised by what I thought was better soil porosity with the rye roots growing in the soil.” Still, he wasn’t sure. He decided to talk it over with Al Miron, a fellow Minnehaha County farmer.

“Lynn was trying cover crops, but was unsure of their value,” Miron says. “He called and we talked about whether the cover crops were doing him any good. He knew I was a long-time no-tiller and that I’ve used cover crops to improve soil health,” Miron says. “We decided to do a series of water infiltration tests, on his ground and mine, to see what we’d find.”

 

Take water infiltration test

They enlisted the help of Extension Soils Field Specialist Anthony Bly of South Dakota State University in Sioux Falls. Bly ran replicated tests on five fields last spring—two on Miron’s farm and three on Boadwine’s farm.

 “It’s a pretty simple test anyone can conduct,” Bly says. “We pounded a 6-inch diameter water infiltration ring about three inches into the ground, and poured a small bottle of water (500 ml) onto the soil in the ring. That simulates about an inch of water. Then we used a stop watch to see how long it took for the water to disappear into the soil. To simulate a bigger rain, and what happens with saturated soil, we poured a second bottle of water after the first one finished soaking in. Then we clocked the total time for both bottles to soak in.”

 

Water infiltration varied greatly

As Boadwine and Miron observed, Bly replicated the test four times in each of the five fields on April 7 and 8. “The soil was relatively dry in all the fields, so the infiltration rates were relatively fast,” Bly says. “Infiltration rates vary with soil moisture, soil type, and other factors—what we were trying to do was compare the rates with different types of tillage, ground cover, and cover crops.”

Bly put together average absorption times for each field and charted the results. The first field was one of Miron’s no-tilled fields, with a cereal rye cover crop growing in the spring that had been aerial-seeded in growing corn in August of 2016. The average time for the first inch of water to soak into the soil was 27 seconds, and the second inch took 3 minutes and 51 seconds. In a nearby location with no-till but without a cover crop, the first inch took 40 seconds to soak in and the second inch took 4 minutes and 46 seconds to soak in.

The third test was on Lynn Boadwine’s farm, in a field harvested for silage with no cover crop, with no tillage done that spring before the test was done. The first inch took 1 minute and 22 seconds to infiltrate, and the second inch took 8 minutes, 8 seconds to soak in. The fourth test was on a Boadwine field harvested for silage with no tillage afterward, but with a radish and oats cover crop established. The first inch soaked into that field in 41 seconds, and the second in 4 minutes and 29 seconds.

Lynn Betts

Nightcrawlers that live in no-till soils make burrows from the soil surface to deeper in the soil profile. The burrows give water infiltration an assist that doesn’t happen in tilled fields.

The final test was in a field harvested for corn the previous fall that was deep ripped in the fall and then field cultivated and planted to oats just the day before the test. The freshly-tilled field took 9 minutes, 45 seconds to absorb the first inch of water and 27 minutes, 13 seconds for the second inch to infiltrate. That reading was off the charts compared to the non-tilled and cover-cropped fields.

 

Heavy tillage is your enemy

“The infiltration on the field that was manured, deep ripped and field cultivated was terrible,” Boadwine says. “I’m convinced now that heavy tillage is your enemy. I carry a spade with me now, and on the end rows I’ve tilled a lot, when I dig with that tile spade, I can see that the tillage harms soil structure more than it helps.”

Bly says that in the dozens of tests he’s conducted, there have been only a few cases where tilled fields infiltrated faster than no-till fields. “Sometimes a no-till field won’t have much cover, and the pores get plugged,” Bly says. “But by far, no-till fields have better water infiltration.”

“The perception among many farmers is that with no-till, the soil is too firm, like a road that you’ve driven on. They think fluffing up the soil with tillage helps it,” Bly explains. “If the soil is really dry, it can take on some water initially from that fluffing, but it doesn’t last long. The pores are disrupted with tillage. What happens when you throw soil around at the surface is the soil that’s dislodged fills any remaining pores. Then water only slowly leaks into the soil, and the rest runs off.”

Bly says what farmers think is firm soil with no-till is actually good soil structure, with aggregated soils. “Two principles of healthy soils--keeping the soil covered and limiting disturbance of the soil—have a lot to do with better water infiltration,” Bly says.

 

Infiltration tests are eye opener

Miron wasn’t surprised by the test results, because he’d watched similar comparisons a few years earlier on his farm. “I noticed that after years of no-tilling, there was less water running off my farm, but I didn’t know if it was the residue on the soil surface preventing water runoff or if lower runoff was due to improved water infiltration,” Miron says. “When the NRCS came to my farm and I watched the infiltration tests, it was an eye-opener for me. It sticks with me now that once you seal up those pores in the soil with tillage, absorption stops and runoff begins.”

Seeing is believing, Miron says. “We did the tests as a demonstration for a group of farmers from the Ukraine I’ve been working with,” he recalls. “We ran the tests on tilled ground and my no-till ground. They anticipated less runoff on tilled ground, and thought the test was rigged because I had selected the locations for the tests. So I told them to pick the spots. We had the same results again—they were convinced at that point.”

Miron is retired from a career as an animal nutritionist, and has made it his mission to improve soil health on his farm and promote the idea to other farmers. “In 125 years of agriculture we’ve reduced organic matter by 50 percent. That’s not sustainable,” Miron says. When he bought his farm, organic matter levels were 0.7% on the hills and 3% in the valleys. He’s bumped them up to about 5% using no-till and cover crops. He’s on the board of the South Dakota Soil Health Coalition, a farmer-led group that’s promoting soil health practices.

 

Work in progress

“We’re trying to find a way to make things work,” Boadwine says. “We have challenges with timing, to get manure injected and use no-till and cover crops. But when you take all that stover off you need to keep the soil protected—and I think land protection goes hand in hand with water infiltration.

We need to get roots growing in the ground, we’ll need more alfalfa in our rotation to do that, and we’ll have to remember not to mess with the top of the soil. Tilling to make the soil act like a sponge is a fallacy.”

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