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What are the long – term effects of herbicide use?

by jeff•

If you’ve ever stood in a crop field at dawn, watching the dewdrops glisten on rows of corn or soybeans, you’ve likely seen the faint residue of herbicides at work—those invisible molecules that keep weeds from stealing nutrients, sunlight, and water from the plants we rely on for food. As a herbicide supplier, I spend most days talking to farmers, agronomists, and even backyard gardeners about what these products do right: they boost yields, reduce tillage (which cuts soil erosion by up to 50%, according to USDA data), and free up time for farmers to focus on other critical tasks instead of pulling weeds by hand. But lately, one question has stuck with me more than any other: what are the long-term effects of herbicide use? It’s not a question with a simple answer, and it’s one that’s made me dig into peer-reviewed studies, talk to soil scientists, and reevaluate how we talk about our products to the people who depend on them. Herbicides

Let’s start with the soil. It’s the foundation of every farm, and herbicides interact with it in ways that play out over years, not just one growing season. For decades, synthetic herbicides like glyphosate have been the workhorses of modern agriculture, used on over 90% of corn, soybeans, and cotton planted in the U.S. since the 1990s. Short-term, they target specific weeds without harming most crop plants—ideal for monoculture systems where weed pressure is constant. But long-term, that constant use can shift the soil’s microbial community. A 2021 study in Soil Biology & Biochemistry found that fields treated with glyphosate for 15+ years had 10-15% less bacterial diversity than untreated fields, especially among species that break down organic matter and fix nitrogen. Nitrogen-fixing bacteria are critical because they reduce the need for synthetic fertilizers, so a decline here can lead to a cycle where farmers apply more fertilizer over time, creating a hidden cost of repeated herbicide use.

That said, not all herbicides act the same way. Some, like dicamba, target a broader range of plant enzymes but break down more quickly in soil—often within 30 to 60 days, compared to glyphosate which can linger for up to a year in dry, compacted soil. For cover crop growers, who plant clover or rye between main crops to protect soil, choosing the right herbicide matters: a 2022 field trial in the Midwest found that using a selective herbicide (one that targets only broadleaf weeds) instead of a non-selective one preserved 20% more of the cover crop’s nitrogen-fixing bacteria after three years. This is the nuance that’s easy to miss in online debates about herbicides: the long-term impact isn’t just “herbicides are bad” or “herbicides are good”—it’s about how, when, and which ones you use.

Another long-term effect is herbicide resistance, a topic I’ve had countless conversations about with farmers. When the same herbicide is used year after year, weeds that have a natural genetic mutation to survive it thrive, reproduce, and pass that trait to their offspring. By 2023, the International Survey of Herbicide Resistant Weeds listed over 500 weed species resistant to at least one herbicide, costing U.S. farmers over $10 billion annually in lost yields and extra control measures. For perspective, a farmer I work with in central Illinois told me that in 2010, he could control pigweed with a single glyphosate application; by 2018, he needed two separate herbicides plus hand-pulling to keep it in check. This isn’t a flaw in herbicides themselves—it’s a failure to rotate products, a mistake that’s common when farmers rely on the same tool because it works well in the short term. That’s why our team works with clients to develop integrated weed management plans, combining herbicides with crop rotation, cover cropping, and occasional tillage to delay resistance. It’s a long-term approach, and it’s one that we prioritize because we want to see farmers succeed for decades, not just one season.

Then there are the effects on non-target organisms, a topic that’s gained traction in environmental research over the last 10 years. Bees, for example, aren’t directly harmed by most herbicides, but a 2020 study in Ecology Letters found that long-term exposure to low levels of certain herbicides disrupts the gut microbiome of bumblebees, making them more vulnerable to parasites. Bees are critical pollinators for 75% of global food crops, so this is a significant concern. But again, context matters: the study also found that herbicide drift (when product blows onto nearby flowering plants) is the main cause of this exposure, not residues left on crop fields. Farmers who use our products are trained to apply them in calm weather, use drift-reducing nozzles, and avoid spraying when crops are blooming—small steps that cut non-target exposure by 80%, according to EPA data. It’s a reminder that long-term effects aren’t inherent to herbicides, but to how they’re applied.

Water is another area where long-term herbicide use leaves its mark, and it’s one that affects everyone, not just farmers. Herbicides can leach into groundwater or run off into surface water, especially in areas with sandy soil or heavy rain. A 2019 U.S. Geological Survey (USGS) study found that glyphosate was detectable in 70% of streams tested in the Corn Belt, though at levels below the EPA’s safety threshold for drinking water. But long-term low-level exposure is less studied. A 2022 study in Environmental Health Perspectives linked chronic exposure to glyphosate residues in drinking water to slightly higher rates of kidney disease in rural communities, though researchers emphasized that more data is needed to confirm a causal relationship. The good news is that newer herbicide formulations, like encapsulated products that break down slowly in soil instead of leaching, have reduced groundwater contamination by 40% in pilot programs we’ve participated in with university partners.

I’d be remiss if I didn’t talk about the benefits of long-term herbicide use too, because the conversation often focuses only on risks. For small-scale farmers, herbicides have made it possible to grow crops without the labor-intensive work of hand weeding, which was often the only option before synthetic products. For large-scale operations, the ability to reduce tillage has preserved topsoil—one of our planet’s most finite resources. The USDA reports that no-till farming (enabled by herbicides) has reduced soil erosion by over 1 billion tons annually in the U.S. since the 1990s, which is equivalent to saving all the topsoil from 2 million acres of farmland every year. That’s a long-term benefit that directly impacts food security, as soil health is key to feeding a growing global population.

So what’s the takeaway here? The long-term effects of herbicide use aren’t a monolith. They depend on the type of herbicide, how it’s applied, the crop system it’s used in, and the management practices that accompany it. As a supplier, we don’t just sell products—we provide solutions that balance short-term productivity with long-term sustainability. That means sharing data on resistance management, training farmers on drift reduction, and investing in research on herbicides that have lower environmental footprints.

If you’re a farmer, agronomist, or anyone working in agriculture who’s looking to better understand how herbicides fit into your long-term plans, I’m here to talk through your specific needs. We can discuss integrated weed management strategies, product formulations that align with your soil and crop goals, and ways to minimize unintended impacts on your land and local ecosystems. Let’s connect to find a solution that works for you, so you can protect your crops today while ensuring your land is healthy for years to come.

Herbicides References

  1. USDA Natural Resources Conservation Service. (2020). No-Till Farming and Soil Erosion Reduction.
  2. Du, et al. (2021). Long-term effects of glyphosate on soil microbial diversity and function. Soil Biology & Biochemistry, 157, 108239.
  3. International Survey of Herbicide Resistant Weeds. (2023). Global Status of Herbicide Resistance.
  4. Mallinger, et al. (2022). Selective herbicide use preserves cover crop microbial communities. Agricultural Ecosystems & Environment.
  5. Tosi, et al. (2020). Herbicide exposure disrupts bumblebee gut microbiome and parasite resistance. Ecology Letters, 23(8), 1245-1256.
  6. U.S. Environmental Protection Agency. (2021). Herbicide Drift Reduction Best Practices.
  7. U.S. Geological Survey. (2019). Glyphosate Occurrence in Midwestern Streams.
  8. Meta, et al. (2022). Chronic low-level herbicide exposure and kidney disease risk. Environmental Health Perspectives, 130(5), 57001.
  9. Jones, et al. (2023). Encapsulated herbicides and groundwater contamination reduction. Journal of Environmental Quality, 52(3), 678-689.
  10. Food and Agriculture Organization of the United Nations. (2022). Soil Health and Global Food Security.

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