Perspective: The remarkable interaction between glyphosate and soil

jack dewitt


I was browsing the Internet the other day, looking for ideas to write about. I came across an opinion written by a Canadian farmer who publishes in a Canadian newspaper, the Financial Post. The title was “Organic farming gets all the hype, but it doesn’t feed the world” by Toban Dyck. His was an opinion I could agree with, so I scrolled down to look at the comments. One from NRN (Not Real Name) caught my eye. He says, “Yesterday I was driving the Southern SK (Saskatchewan) countryside. Mile after mile of chem-fallow with 3-inch high dead standing stubble. It looked devoid of life. Hard even for insects to survive in that. No birds were around. I know organic cannot feed the world, but don’t try to convince me that industrial ag is sustainable.”

Well, I thought, NRN and those with a similar view might benefit from a farmer’s perspective. So I wrote him an open letter:

NRN, I know your opinion is shared by many people removed a few generations from the farm. But consider a few things that are not apparent when you look at those fields while driving by at 100 kilometers per hour (62 mph). First of all those “industrial” farms are likely owned by family farmers who bristle at the word industrial, because they care deeply about the soils and livestock that provide their livelihood. “Industrial” implies a non-caring, profit-only mind-set. A way of life, profit or not, is the attitude of family farmers. Sure, they may farm lots of acres with big machinery, but that’s what it takes to make a living these days, and it doesn’t mean they don’t take care of their land and livestock.

Those fields “devoid of life” are deceiving. You see, that 3-inch stubble is protecting the soil from wind or water erosion, and providing food and cover for insects and no doubt for some birds that prefer the open prairie. If you had stopped and walked out into a field with a shovel you would find, under the cover of straw, moist soil supporting billions of microbes at work digesting organic matter and making nutrients available for the next crop. Earthworms may not be numerous, but they would be at work there also. The cover of straw will keep the soil cool and moist well into the hot summer, and in the fall or next spring, the farmer will likely direct-seed canola, wheat, peas or some other crop. His/her machine will disturb the soil and its hard-working inhabitants hardly at all. Or, you might find there is already a crop growing, having been direct-seeded a few weeks ago and not yet tall enough to be seen from the road.

The fields have most likely been sprayed with Roundup, and that may disturb you. The International Agency for Research on Cancer (IARC) has declared glyphosate, the active ingredient in Roundup, a “probable” human carcinogen, a decision that has triggered thousands of lawsuits. So far, three trials have been completed, and juries have found in favor of the plaintiffs. That does not prove Roundup causes cancer: Juries are not generally good judges of scientific arguments. There are some studies that claim to prove glyphosate is a carcinogen, and nearly a thousand that claim it is not. The IARC chose to put the chemical in the same “probable” category as working the night shift, eating barbecued meat and french fries, and working in a beauty shop.

To a farmer, Roundup is a wonder chemical that has allowed direct-seed farming to develop. You see, a farmer can spray a weedy field or a cover crop with Roundup one day and seed it the next day without tilling the soil. Roundup slowly kills most everything green but leaves no residue harmful to the newly seeded crop. Roundup also will not harm the soil biota or the insects, or birds and other animals that may inhabit the field. No other herbicide comes close to this portfolio of favorable attributes. By reducing tillage and encouraging a perpetual cover over the soil, Roundup has prevented the erosion of billions of tons of topsoil over the last 40 years.

Glyphosate kills plants by disrupting the shikimate pathway in plants. The shikimate pathway is part of the plant machinery that manufactures the amino acids phenylalanine, tyrosine, and tryptophan, all of which are essential to growth and maintenance of a plant. They are also essential to growth and maintenance of animals, but animals, including humans, must get them from plants (beans, nuts) and products from animals that consume plants (eggs, milk, beef), because animals and invertebrates do not possess the shikimate pathway and cannot make these amino acids. That is why glyphosate is considered nontoxic to humans. If we consume it in tiny amounts, it is quickly discarded by the kidneys and liver.

Glyphosate droplets that hit the soil are quickly deactivated. The glyphosate molecule carries both a negative and a positive charge: negative on both ends and positive in the center (such molecules are called zwitterions), as explained by Dr. Stephen Duke of the University of Mississippi. Deactivation is principally caused by chemically binding to iron and aluminum oxides in the soil, and to other metal ions that may be available such as copper. These bonds are soon attacked by various soil bacteria and other organisms that tear the molecule apart to use the carbon, nitrogen and phosphorous the molecule contains, completely destroying the molecule and recycling the nutrients for eventual plant uptake. Some of the glyphosate may also displace phosphorous anions bound to clay particles, a more permanent bond that can last for years in some cases.

A decade or two ago, your trip would have passed by fields turned black or brown from tillage. They would have no residue to protect the soil from wind or water erosion. Birds would have no cover, and surface insects would be few if any. The soil biota would have a feeding frenzy on the buried residue, then crash when it was all used up. Roundup has been a soil conservation promoter like no other in the last 40 years. It would be a huge setback for conservation, for sustainability, and for food production in general, if it were ever banned.


Jack DeWitt is a farmer-agronomist with farming experience that spans the decades since the end of horse farming to the age of GPS and precision farming. He recounts all and predicts how we can have a future world with abundant food in his book “World Food Unlimited.” This article was republished from Agri-Times Northwest with permission.

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