On 2015 Sep 05, Andrew R Kniss commented:

It is certainly plausible that herbicides (glyphosate or other) might have some direct effect on earthworms. However, due to the design flaws, these effects cannot be evaluated from this particular study. The problems with this paper boil down to two main points:

1) One of the herbicides applied in the study was "Roundup Speed" which contains the herbicide pelargonic acid in addition to glyphosate, so it is impossible to conclude anything about the direct effects of glyphosate. 2) More importantly, the researchers didn't include a control treatment where they killed the plants without herbicides. All of the effects on earthworms and nutrients observed in this study could simply be due to killing the plants. It is perfectly plausible the exact same effects would be observed if the plants were clipped or pulled out of the pots.

In addition, the glyphosate rate used in this study is far greater than would be used in field applications of this product. I calculated the amount of glyphosate applied to the pots (adding up the three applications they made) and converted it into the amount of glyphosate per unit area. It turns out the amount of glyphosate applied to each pot is equivalent to a field rate of 12,680 grams per hectare. A typical application rate in a field of glyphosate-resistant crops would be somewhere between 800 to 1,300 grams per hectare. So the amount of glyphosate they applied is about an order of magnitude too high to be relevant to most field situations.

Blog post with more detail: http://weedcontrolfreaks.com/2015/09/dead-plants-are-probably-bad-for-earthworms/

On 2015 Sep 05, Andrew R Kniss commented:

It is certainly plausible that herbicides (glyphosate or other) might have some direct effect on earthworms. However, due to the design flaws, these effects cannot be evaluated from this particular study. The problems with this paper boil down to two main points:

1) One of the herbicides applied in the study was "Roundup Speed" which contains the herbicide pelargonic acid in addition to glyphosate, so it is impossible to conclude anything about the direct effects of glyphosate. 2) More importantly, the researchers didn't include a control treatment where they killed the plants without herbicides. All of the effects on earthworms and nutrients observed in this study could simply be due to killing the plants. It is perfectly plausible the exact same effects would be observed if the plants were clipped or pulled out of the pots.

In addition, the glyphosate rate used in this study is far greater than would be used in field applications of this product. I calculated the amount of glyphosate applied to the pots (adding up the three applications they made) and converted it into the amount of glyphosate per unit area. It turns out the amount of glyphosate applied to each pot is equivalent to a field rate of 12,680 grams per hectare. A typical application rate in a field of glyphosate-resistant crops would be somewhere between 800 to 1,300 grams per hectare. So the amount of glyphosate they applied is about an order of magnitude too high to be relevant to most field situations.

Blog post with more detail: http://weedcontrolfreaks.com/2015/09/dead-plants-are-probably-bad-for-earthworms/