It is known that glyphosate is toxic to the bacteria, which
forms nodules and fixes nitrogen in soybeans, when the bacteria
is grown in direct contact with glyphosate in petri dishes.
However, does glyphosate affect the bacteria in the roots of
Roundup Ready (RR) soybeans? Researchers in Arkansas (King and
others) tested this question by spraying inoculated RR soybeans
in nitrogen-free soil in the greenhouse. When the RR soybean
seedlings were sprayed twice with 1.5 qt/a of Roundup Ultra (at
5 days after emergence and again at 10 days after emergence),
there was a reduction in the weight of the nodules and a slight
reduction in the shoot weight at 9 days after the second
glyphosate application. However, by 30 days after the second
glyphosate application, the soybeans recovered. The shoot
weights, nodule weights, and nitrogen concentration in the
soybeans were the same if sprayed with glyphosate or not. They
also sprayed larger soybeans three times with 1.5 qt/a of
Roundup Ultra (at 18, 25, and 32 days after e