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Glyphosate has much less influence on nutrients in crops than has been thought for years. A small-scale student test is the likely cause of misconceptions about this herbicide. This is apparent from a reconstruction of two decades of research into the effects of glyphosate on nutrients in crops, carried out by the popular scientific magazine Plant nutrition courier.
Glyphosate binds to calcium and magnesium, manganese and zinc. Other nutrients such as copper and iron can also be chelated (sequestered) by this active ingredient. Researchers disagree about the circumstances under which this occurs: only in the sprayer tank, or also in plants. The controversy can be traced to a small-scale student test, according to a reconstruction of two decades of research into the effects of glyphosate on the nutritional status of crops. The test was conducted around 2000 by a student from Purdue University (USA). The previous history and aftermath of this trial have been mapped by the popular science magazine Plant nutrition courier.
Yellow soy
The reason for the student trial was the then unexplained yellow coloration (‘yellow flash’) of glyphosate-resistant soy, shortly after spraying with this herbicide. The symptoms are reminiscent of manganese deficiency, a well-known phenomenon for soy growers on calcareous soils. The student test was conducted with two varieties: a glyphosate-resistant variety and a cultivar that was sensitive to glyphosate. The glyphosate-resistant variety cannot properly take up the required nutrients from the soil, is the firm conclusion of the student and his supervisor. A more extensive follow-up test yields conflicting results, but the conclusion is maintained and is even extended with the statement that glyphosate itself also hinders the uptake of nutrients. The results of these tests are widely circulated in lectures and alarming articles. However, other researchers later show that a degradation product of glyphosate has caused the temporary yellowing in soy.
Other researchers also report to measure lower levels of nutrients in glyphosate-resistant crops, but critics point to the incorrect or limited design of some of these tests and the disputable conclusions drawn from these and other studies. New research results have also been reported in recent years that prove the contrary. In these tests, glyphosate doesn’t affect nutrient contents in glyphosate-resistant crops.
Ongoing discussion
Despite ever better research techniques, the assumed chelation of nutrients by glyphosate has never been demonstrated in plants, according to the analysis of the Plant nutrition courier. Nevertheless, the discussion continues and there are farmers who unnecessary provide their crops with additional nutrients. And still very recently German researchers have questioned the risk analyses of the European Food Safety Authority (EFSA). In their eyes, this agency of the European Union has not adequately considered studies the researchers think to show the binding of nutrients.