Commentary: A Pesticide-Free Farm Can Have Worse Soil Than One Sprayed With Roundup

Ten weeks before the midterm elections, a weed killer is threatening to split one of President Donald Trump’s political alliances.

The Washington Post reported Wednesday that anger over pesticides is straining the relationship between Trump’s MAGA movement and Robert F. Kennedy Jr.’s Make America Healthy Again movement. Some MAHA activists are even targeting Trump’s nominee to lead the Food and Drug Administration over the administration’s support for domestic glyphosate production.

Their argument sounds reasonable. Use fewer pesticides and farms become healthier.

Not necessarily.

A pesticide-free farm can have worse soil than one sprayed with Roundup.

That sounds backward. I once would have thought so too. But in my work studying soil microbial communities, I have learned how poorly labels such as “natural,” “chemical,” and “regenerative” describe what is actually happening underground.

Start with weeds. They have to be controlled. A farmer can kill them with an herbicide. Or a farmer can cut, uproot, and bury them by repeatedly disturbing the soil.

Glyphosate made the first option cheap and effective enough that many farmers could till less. Research on U.S. soybean farms found that the arrival of glyphosate-tolerant soybeans increased conservation tillage by about 10 percent.

That matters because tillage does much more than remove weeds.

USDA warns that tillage breaks down soil structure, reduces water infiltration, increases runoff and erosion, and destroys habitat used by soil organisms. Soil is crowded with bacteria, fungi, and other organisms that cycle nutrients and interact with plant roots. They live in pores and around soil aggregates. Run steel through that habitat year after year, and you change it.

We also have evidence of what happens when glyphosate stops working well.

Researchers followed soybean management across the United States from 1998 through 2016 as glyphosate-resistant weeds spread. With no resistant species present, predicted no-till adoption was 44.4 percent. By the time eight resistant weed species were present, no-till use had fallen 7.6 percentage points. That was a 17.1 percent decline among no-till users.

The researchers estimated that the resulting shift toward tillage caused nearly $245 million in water-quality and fuel-emission damages between 2008 and 2016. Their estimate did not include carbon released when soil was disturbed.

This was not a study of a glyphosate ban. But it exposes the problem with treating pesticide reduction itself as proof of environmental progress.

Remove the sprayer and something still has to control the weeds.

Sometimes the replacement will be better. Cover crops, crop rotations, precision spraying, and newer mechanical technologies can reduce reliance on herbicides without returning a field to intensive tillage.

But sometimes the replacement is a cultivator or plow.

Picture two soybean fields.

One receives a limited amount of glyphosate but is rarely tilled and remains covered with crop residue. The other uses no synthetic herbicide but is cultivated repeatedly, exposing and disturbing the soil.

Which field is healthier?

“Pesticide-free” cannot answer that question.

Microbes cannot read labels either. A bacterium does not know that a farm is organic. A fungus has no idea that a practice is called regenerative. What matters underground is what actually happens there. Moisture changes. Roots grow or disappear. Chemicals arrive. Soil gets turned over.

None of this makes glyphosate harmless. Its effects on people and ecosystems deserve scrutiny. Nor does it mean farmers should spray more of it.

It means we should stop judging a farm by one chemical.

That point matters now because the Trump administration is trying to satisfy two goals at once. It is promoting regenerative agriculture and soil health while facing MAHA pressure for tougher action on pesticides.

On some farms, those goals may clash.

Washington should push for ways to reduce herbicide use without driving farmers back toward heavy tillage. Better rotations, cover crops, targeted spraying and new weed-control technologies can help.

But politicians should stop assuming that removing a pesticide automatically makes a field greener.

The better test is down in the dirt.

If Roundup disappears from a farm and the plow comes back, we should not call that an environmental victory before we look at what happened to the soil.