BRANDON – The hilltops in many farmers’ fields look a lot like the tops of many older farmers’ heads: pretty bare, with only a thin, wispy covering.
They’re hardly worth shaving with the combine at harvest.
But farmers don’t need to accept the baldness of their hilltops, David Lobb of the University of Manitoba’s soil science department told farmers at Manitoba Ag Days in Brandon.
It’s a condition that can be reversed and is not an inevitable sign of an aging farming system.
Read Also
VIDEO: Green Lightning and Nytro Ag win sustainability innovation award
Nytro Ag Corp and Green Lightning recieved an innovation award at Ag in Motion 2025 for the Green Lightning Nitrogen Machine, which converts atmospheric nitrogen into a plant-usable form.
“There’s an underutilized resource sitting at the bottom of the hill,” Lobb said.
Research has demonstrated that the barrenness of hilltops isn’t caused by water or wind erosion. The main culprit is tillage, which drags soil downhill on every field operation. Not only does soil naturally slide downhill because of gravity, but farmers also use their machinery differently when going up and down hills. Many farmers need to lift equipment or gear down as they drive up hillsides, bringing little force to the soil that could drag it up. But when going down, the tractor and implements exert far more force on the soil, taking it down the hill.
After decades of this shaving, many hilltops and hill sides become bereft of topsoil, while the lower land at the bottom of the hill ends up with a double layer. Wetlands can become clogged and polluted with the too-rich topsoil.
In bad cases, the hilltop not only loses all of its topsoil, but the infertile and inorganic subsoil begins to be dragged off too, covering the thick layer of topsoil at the bottom of the hill with a layer of subsoil, making it less fertile.
Thousands of farmers have noticed this hilltop problem, and many have hoped to alleviate it by converting to minimum tillage.
They have been disappointed. Nothing happens. The minimum-tilled hilltop remains unproductive.
Lobb said this makes sense, because topsoil takes decades or centuries to build, and a few years of minimum till won’t make up for previous stripping.
But there’s a further problem: minimum tillage is still tillage. Every time the seeder goes through the soil, it’s moving soil. The degree can be surprising.
“The revelation that high disturbance seeders can actually be as erosive as an older plow is pretty controversial,” Lobb said in a later interview.
“If you tell farmers that zero-till isn’t really zero-till, they’re pretty surprised.”
So if the topsoil has been stripped and minimum tillage isn’t the answer, what is to be done?
Lobb’s answer is simple: get the topsoil back to the top of the hill. It’s a concept that may sound crazy to the prairie farmer, but to millions of farmers around the world it was – and is – a common practice.
Lobb showed photographs of French farmers in the 1930s transporting soil at the end of a growing season from the bottom of a field to the top.
Lobb said land rental agreements in France in those days often required farmers to return mobile topsoil to its previous location.
Today, in the terraced paddy fields of Asia, returning topsoil is so common a practice it has a Chinese name: Tiaoshamiantu. Farmers usually do it by scooping soil into baskets and carrying it back to its origin.
Fortunately for North American farmers, there are less labour intensive methods. For example, plows can be used to plow up soil rather than drag it down.
Also, an earth scraper can lift a few inches of soil from low-lying areas and redeposit it on the hilltop. Four to five inches of replaced topsoil can transform a hilltop’s productive capacity.
Lobb said one of the experiments he took part in saw a hilltop’s production increase by 21 percent on the first year in which it had new topsoil and by 83 percent the next year. The effect on the lower land from which topsoil had been removed was minimal.
Lobb said farmers may see earth moving as a demanding process and wish to attempt to simply build up hilltops’ organic matter by cropping. However, he added, that will never happen because those hilltops aren’t producing real organic matter.
“On those eroded hilltops you’ve got almost no potential to produce biomass,” said Lobb.
“Well, it’s never going to recover if it’s not producing biomass. Any recovery that occurs is offset by harrowing or seeding.”
It would make much more sense to practice a bit of Tiaoshamiantu.
