Manage Water with Controlled Traffic

Controlled traffic is an easy way to improve water management and, thus, soil health

This is a question/answer from John Kempf’s Eco Ag U seminar at the 2024 Acres U.S.A. conference.

Q: I’m from Maine, and this year we dealt with 20 inches of rain. But I know the rest of the country is struggling with drought. What’s a more regenerative approach to water management that works in all these different contexts?

John Kempf: There are a lot of aspects to managing water in the soil profile, as well as to managing water for the crop. We’ve already demonstrated that you can achieve the same overall yields and crop performance with 50 percent less water when you manage nutrition differently. That’s relevant for drought stress and managing low-rainfall environments.

And then, in a high-rainfall environment, as plants become healthier, they don’t stress as easily, and they don’t suffer from oxygen deprivation as rapidly when soils are saturated.

But the question of excessive rain is not a question about infiltration but about percolation. Percolation is a word that has largely been forgotten in our agronomy today. There’s this desire to focus on water infiltration rates. But percolation is just as important.

Back when soils were farmed with horses, there was of course lots of soil mismanagement in that era, but there wasn’t deep compaction caused by large, heavy machinery. There was a much better understanding of percolation — the ability of soil to quickly move water down deep, and quickly back up. That’s called percolation.

Of the many aspects of Gabe Brown’s story that are so inspiring, the piece that inspired me perhaps more than any other was his describing how soil cores from his farm that were four feet deep only had two feet of soil inside the core. In other words, his soils had 50 percent airspace all the way down to a four-foot depth. That gives you the ability to infiltrate a tremendous amount of water down deep quickly and percolate it back up quickly. Those types of soils could probably handle 20 inches of rainfall in a month, because the water can move down and can move back up. That function is severely degraded in most soils today.

But we have an example of a much better practice today in the southern hemisphere — many leading large-scale farmers in Australia run strictly controlled traffic on their entire farming operations. They drive their tractors only on the exact same tram lines. They are not compressing and putting pressure on any of their soil profile except those tram lines. This is becoming standard operating procedure on many broadacre farms.

And yet here in North America, we haven’t adopted this practice, for the most part. Why not? Because the situation hasn’t become bad enough yet. That’s the unfortunate truth. The stress hasn’t become significant enough yet.

I was at Loren Steinlage’s farm roughly four years ago, in northeastern Iowa, and Loren’s farm has been completely controlled traffic for at least a decade. Two years before I was there, they had hosted a field day and had dug a soil pit to view the soil profile. When they filled the soil pit back in, all the soil went back into the pit, without making a mound. And when I was there two years later, you could still see the spot, because it was now a depression — it was six to eight inches lower than everywhere else.

Digging the soil out of the pit had caused a significant loss of soil structure. That tells me that he had tremendous amount of airspace throughout the soil profile. And that came about as a result of controlled traffic.

For the life of me, I can’t figure out why we don’t do controlled traffic. It’s such a fundamental, easy thing to change. It really changes soil health and soil profile, and yet most people don’t want to do it.