In theory you use less. Roundup Ready is supposed to use lower quantities of weedkiller but do so earlier in the growing season when everything is more vulnerable to it (thus making a resistant crop useful).
It's not a great sales slogan: "Roundup Ready - increases costs by increasing the amount of spraying you can do".
1995: Be very careful with weedicides... a few drops on our crops will kill them.
2015: Just spray the whole field... weeds, crops and all.
How roundup-ready crops are sold as a good thing, I really have no idea. Somehow the world has been convinced that dousing their food in weedicide isn't a bad idea.
"Glyphosate and its degradation product, AMPA, residues are considered to be much more toxicologically and environmentally benign than most of the herbicides replaced by glyphosate."
Like the above poster said, it's how they're applied.
I live next door to this. Every year my vineyard is blasted by idiots growing corn or soy (farmed by subcontracts of leases off my neighbours land, nice and hands off). Because it's Roundup Ready they don't care or think, they just blast. It's an ecological nightmare.
I'm not concerned about my health, I think glyphosate is mostly harmless to humans. I'm concerned about ecological diversity -- I have a bush lot, I can see the immediate damage this stuff causes to native plants.
Last year I took the growers pesticide training course here. It was very enlightening to see from the co-participants in my class just how derisive they were of the general public's concern about their large scale use of pesticides in areas they consider "theirs", as if there are no neighbours, human or natural.
And it's not like we're talking farmers growing 'food' next door -- it's soy or corn for animal feed. The land owner gets $150 an acre. It's barely profitable. It's stripped the life out of the top soil, so if you factored in the actual value of the land over 50 years, it's probably negative profit considering the permanent topsoil depletion.
It's a stupid way to organize human affairs, a total short term waste of precious expendable resources. Modern industrial agriculture is moronic and technocratic arm-chair libertarian justifiers of it who read a couple articles in The Economist and watch a TED talk are complicit in its ugliness.
