It may prove difficult for some folks to believe, but recent University of Nebraska research work indicates that glyphosate applications may result in fluctuations in the nitrogen status of Roundup Ready soybeans.

In several research trials, the chlorophyll content was reduced after nearly every glyphosate application, which probably created periods of decreased nitrogen levels.

“Though this research, we can see that although the glyphosate resistant soybean is able to tolerate glyphosate, it is incorrect to think that the plant is completely unaffected by this herbicide,” says Lori Abendroth.

Chlorophyll Vs. Nitrogen

The Nebraska agronomist says the chlorophyll content that is often referred to as the “greenness” of the leaf is used to reference the amount of nitrogen contained within the plant. When a plant that experiences nitrogen stress becomes yellow, it is seen as a reduction in chlorophyll.

As atmospheric nitrogen is converted by the nitrogen-fixing bacteria to nitrogen compounds that are usable by the plant, Abendroth says they are transported to the above-ground portion of the soybean plant. When glyphosate is applied to the soybean plant, it is moved downward and can possibly interfere with the nitrogen-fixing process.

“If an inhibition does occur within the nodules, we would expect to see less nitrogen being moved to the leaves,” she says. “Nitrogen moves in a cyclical pattern within the plant and nodules will respond to nitrogen stress by converting more nitrogen to meet the demands of the growing plant.

“Once the plant has enough nitrogen, the bacteria conversion process will…