When we think about glyphosate, we often picture its immediate effect — weeds withering and dying after being sprayed.
But what about the longer-term impact on the very soil it’s sprayed onto? While glyphosate is marketed as a broad-spectrum herbicide, its presence in the soil may be causing a far bigger problem than we realize.
In agriculture, healthy soil is everything. It’s the foundation for plant growth, nutrient cycling, and biodiversity. Yet, evidence is mounting that glyphosate — and its breakdown product AMPA — might be quietly degrading that foundation.
Breaking Down, But Not Breaking Free
Glyphosate doesn’t just vanish after application. It binds tightly to soil particles and can persist for months — or even longer in certain environmental conditions. The herbicide’s breakdown product, AMPA (aminomethylphosphonic acid), is even more persistent.
But it’s not just the persistence that’s concerning — it’s what happens while it’s in the soil.
Soil Microbes: The Invisible Casualties
Glyphosate targets the shikimate pathway, which is present in plants and many microorganisms but not in animals. This has led to the assumption that it’s harmless to humans and other non-plant life. But here’s the problem: soil microbes do have this pathway, and they play a crucial role in maintaining soil health.
- Bacterial Imbalance: Some studies show that glyphosate reduces beneficial soil bacteria like Pseudomonas and Bacillus, while allowing potentially harmful pathogens to thrive.
- Fungal Disruption: Fungi that help decompose organic matter and support plant roots can also be negatively affected, leading to reduced soil fertility.
- Reduced Nutrient Availability: By disrupting microbial communities, glyphosate can decrease the availability of essential nutrients like nitrogen and phosphorus.
If soil microbes are disrupted, the entire ecosystem suffers. It’s like pulling threads from a tapestry — eventually, the whole thing unravels.
The Earthworm Dilemma
Earthworms are often called the engineers of the soil. They aerate, decompose organic material, and improve soil structure. But studies have shown that exposure to glyphosate and its byproduct AMPA can reduce earthworm reproduction, alter behavior, and decrease survival rates.
One study found that glyphosate exposure led to decreased casting activity — the natural process by which earthworms move soil and deposit nutrient-rich castings on the surface. Without this activity, soil quality declines, and plant health can suffer.
Why are we risking the loss of these essential soil engineers for the sake of killing weeds?
The Myth of Safe Residues
One of the biggest misconceptions about glyphosate is that it breaks down quickly and harmlessly. While it’s true that glyphosate eventually degrades, the timeframe is highly variable. In low-oxygen environments, like compacted or waterlogged soils, glyphosate can persist even longer.
When AMPA remains in the soil, it doesn’t just sit there harmlessly. Studies suggest that AMPA itself can disrupt microbial balance, interfere with root development, and even increase soil acidity, affecting long-term fertility.
If glyphosate’s breakdown product is just as problematic — or even more so — shouldn’t we be more cautious about widespread use?
Agriculture’s Invisible Cost
New Zealand’s agriculture sector is heavily reliant on glyphosate for weed management, but that’s not the whole story. Glyphosate is also sprayed on some crops just before harvest as a desiccant — a practice intended to speed up drying and make harvesting easier. This means that residues can end up directly on food crops and persist in the soil after harvest.
While farmers may see short-term gains from glyphosate use, the long-term consequences could include:
- Lower yields: Due to nutrient depletion and reduced microbial support.
- Soil degradation: Less organic matter and poorer soil structure.
- Increased residues: Spraying before harvest can lead to higher glyphosate levels remaining in the soil and in the harvested crop.
When soil health declines, it’s not just an agricultural problem — it’s an environmental and economic one.
Why Aren’t We Talking About This?
Despite growing evidence, the discussion around glyphosate remains narrowly focused on its direct toxicity rather than its ecosystem impact. Regulators focus on residue limits rather than the cumulative effects on soil biodiversity.
If glyphosate is so safe, why are scientists raising alarms about its long-term impact on soil health? Are we too focused on short-term agricultural efficiency to consider the broader ecological damage?
Final Thought
Soil is more than just dirt — it’s a living, breathing ecosystem. When we compromise it, we compromise our food security, biodiversity, and long-term agricultural sustainability. Glyphosate’s impact on soil health may be one of the most overlooked aspects of its use.
If protecting our soil means rethinking glyphosate, then it’s time to ask harder questions about what we’re willing to sacrifice for convenience.
Resources & References
Curious to dig deeper? Here’s a collection of resources that challenge assumptions and shed light on the claims we’ve covered in this article. Dive in and see what the research really says.
The Impact of Glyphosate on Soil Health
This comprehensive report by the Soil Association reviews scientific evidence on glyphosate’s effects on soil organisms, highlighting concerns about its persistence and potential to harm beneficial microbes.
Read the full report [PDF]
Effects of Glyphosate on Earthworms: From Fears to Facts
Published in the journal Integrated Environmental Assessment and Management, this study examines the sub-lethal effects of glyphosate on earthworms, including impacts on reproduction and behavior.
Access the study
Persistence of Glyphosate and AMPA in Agricultural Soils
This research article explores how glyphosate and its primary metabolite, AMPA, persist in different soil types, emphasizing factors that influence their degradation rates.
View the article
Effects of Glyphosate-Based Herbicides on Earthworms and Soil Functions
Published in Environmental Sciences Europe, this study investigates how both glyphosate and its commercial formulations affect earthworm activity and soil health, noting significant alterations in soil functions.
Read the study
Beneath the Orange Fields: Impact of Glyphosate on Soil Organisms
This briefing by PAN Europe summarizes findings on glyphosate’s detrimental effects on soil organisms, including disruptions to microbial communities and earthworm populations.
Download the briefing [PDF]
Dynamics of Glyphosate and Aminomethylphosphonic Acid in Soil
This study examines the degradation patterns of glyphosate and AMPA in soil, providing insights into their long-term environmental impacts.
Access the research
These resources offer a deeper understanding of the potential risks associated with glyphosate use, particularly concerning soil health and ecosystem integrity. For further information or specific inquiries about any of these topics, feel free to ask!
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