When I read this headline I had to rub my eyes and make sure of what I was seeing: 

Why a long-term no-tiller is plowing again on heavy soils …

Obviously this goes against many of the concepts we emphasize in No-Till Farmer. But I was interested in understanding the “why” behind this farmer’s decision, detailed in the pages of Farmers Weekly. So here it goes: 

Simon Cowell of Motts Farm in Essex, U.K. has been no-tilling for 20 years, where he raises wheat and a variety of other crops. He started no-tilling the farm’s predominantly heavy clay soils in the 1990s because of the challenges in establishing crops. 

No-till was a revolution, he told Farmers Weekly, as it transformed soil structure, improving trafficability, increasing biological activity and lowering input costs. It also allowed him to bring spring crops back into the rotation.

But after all this time, Cowell says he started seeing issues that perplexed him. Among other things, wheat and linseed yields had somewhat stagnated, not reaching highs he achieved before no-tilling.

With one whole field and part of a second field he turned to tillage with a Kverneland manual variable-width plow. He wanted to see if plowing once every 6-10 years could make a difference and improve yields. 

But that’s not the only reason. He detailed others: 

• He’s raising corps on old dairy farm and Cowell says he still has areas that have been permanent pasture since land was reclaimed from the sea roughly 300 years ago. In that time only 4 inches of topsoil has built up, he says. 

“I’ve always thought we could keep sequestering carbon and building organic matter and that layer would keep getting deeper. But it seems there is a natural limit,” he tells Farmers Weekly. “And in my arable fields I’ve already achieved that after 20 years. The scientists say you reach carbon saturation, and I think that’s what I’ve reached.”

But in the 20-plus years since switching to no-till, soil organic matter has increased from 3.5% to roughly 8%, with some help from applications of compost. 

• He also says earthworms aren’t taking wheat straw down anymore. When he started no-tilling chopped straw disappeared in 8 weeks. But in the last 5 years he says worms have lost interest. Cowell thinks it’s because the soil doesn’t need more carbon, “and the worms have enough to live on by cycling what’s in the soil already.” 

So he believed turning the soil would restart the process, mineralizing nitrogen and other nutrients in the process. He told the magazine, “When you’re direct drilling, you’re immobilizing nutrients to some degree if you’re building organic matter.

“There’s a 10:1 carbon-to-nitrogen ratio in organic matter, which means for every ton of carbon you put down, there’s 200 pounds of nitrogen you are tying up in the organic matter – it’s the same for other nutrients tied up in organic matter."

“And while the theory is you should get more nutrient cycling when the soil biology is working, it’s not going to be as much if you’re also building organic matter, as it is tying up more than it is releasing – otherwise it wouldn’t be building.” He suggests if that’s true, building organic matter has a nutrient cost.

As the growing season continues Cowell plans to compare wheat established following plowing in one of the fields with no-till in the same field. He will pull soil tests to see whether plowing mineralized organic matter and he seeks to quantify how much carbon has been lost.

Yields will also be compared in wheat this year, where the plowed land could only be planted 2 weeks after the direct-drilled crop.

A second field intended for spring linseed was plowed in November, with a neighboring field being used to compare. He’s hopes mixing deeper clay soil with the higher organic matter topsoil might reduce the impact of stratification.

• Cowell’s last reason for plowing comes after reading a book by Russian soil microbiologist Nikolai Krasilnikov. The book discusses the potential negative impacts on crop growth from toxic chemicals produced by crops and microbes. It’s not just root exudates but also bacteria associated with a crop that will prevent other plants growing, he argues.

“It seems these chemicals are pretty persistent, particularly in clay soils, and I’m wondering whether in a direct-drilling situation they’re hanging around and reducing yields. Krasilnikov suggests plowed soils have lower amounts of these toxic substances.”

Cowell says the decline in yields from some break crops, such as peas, on the farm has reached a point where he no longer grows them, which he sees as possible anecdotal evidence of this phenomenon.

Yield and cost will determine whether plowing becomes a more frequent practice. He’s working to pencil out what yield response is needed to justify the costs of plowing.

One thing the article doesn’t delve into is Cowell’s fertilizer or crop protection practices, soil tests or other data that might indicate whether something is out of balance in his soils due to natural causes or his own management decisions.

Having said that, I’m curious to see what our readers think about the questions raised here: Do earthworms really go underground permanently when their environment is saturated with carbon? Are your no-tilled soils stratified, and is it a problem? Does it really pay to reset the profile, so to speak? 

Feel free to sound off!