The Real Dirt on no-Till: Why Herbicides Aren't Saving the Environment

No-till corn reduces erosion over moldboard plowing--but is it the only way?

Tillage is bad. That’s the message I was getting in all of my agronomy classes at Ohio State. No-till farming was the most environmentally friendly system ever developed. It reduced soil erosion, kept the soil surface covered year-round, added organic matter to the top few inches of soil, and left all those wonderful earthworm tunnels and root channels intact.

But it only worked with chemicals. The only way to do no-till, I was told, was by spraying the fields with glyphosate to “terminate” weeds and cover crops. For best results, it was also important to plant genetically modified glyphosate-resistant crop plants—which were the most environmentally friendly invention ever! I was also told that organic farming must automatically be bad for the environment because the only alternative to herbicides was the moldboard plow and constant cultivation, which would leave bare dirt year-round and cause serious soil erosion.

I was always a little skeptical of the claim that the only way to protect the environment was to use herbicides. But it wasn’t until I learned about the Universal Soil Loss Equation (USLE) in my soil conservation class that I was finally able to do some calculations for myself. The USLE is what the USDA’s Natural Resources Conservation Service uses to compare erosion rates under different tillage systems. Farmers can influence erosion rates in two ways—through cropping practices (type of crop and tillage system) and supporting practices (contour plowing, strip cropping, and terracing).

According to the USLE, herbicide-dependent no-till corn has 87% less erosion than fall plowing with a moldboard. But there are other ways to reduce erosion. Using a chisel plow on corn, for example, reduces erosion by 50% over a moldboard. So does planting and cultivating on the contour. Erosion is reduced 75% if the field is chisel-plowed on the contour. If that chisel-plowed corn is strip-cropped with a small grain or grass, erosion is reduced just as much as with no-till—with no herbicides at all! Even better, planting a steep slope in grass reduces erosion by 96% over moldboard-plowed corn—twice as effective as no-till corn. No-till’s not the only—or even the best—way to reduce soil erosion.

But the USLE is just a model. What’s happening in the real world? I looked at the NRCS’s National Resources Inventory, which has measured soil erosion since 1977, and it turns out that herbicide-dependent no-till hasn’t actually reduced soil erosion at all on a national level. Between 1982 and 1997, soil erosion in the United States decreased by 40%—mostly due to the increased use of non-chemical conservation tillage techniques like chisel plowing. Ever since the first glyphosate-resistant soybeans were released in 1996, soil erosion rates at a national level have not decreased at all. They’ve actually gone up a little.

So guess what? It’s the tried-and-true nonchemical soil conservation methods—chisel plowing, contouring, strip cropping, and grass farming—that have achieved the only measurable reductions in soil erosion in US history. Organic farmers use all of those practices, usually at a higher rate than conventional farmers. So don’t believe the chemical companies when they say that their products are better for the environment than organic farming. They’re not. Herbicide-dependent no-till hasn’t significantly reduced soil erosion or helped the environment at all. The claim that it has is just chemical company propaganda.