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.
"Are hybrid seeds designed to be one use only like terminator seeds? How is the vendor lock-in structured?"
Plant breeding 101:
Every individual has two copies of each gene: one comes form the father, on from the mother. It has been observed that individuals who mostly have different maternal and paternal versions, are more vigorous. This is called heterosis, or hybrid vigor [1].
Now, just to produce children with a high number of genes that have different paternal and maternal copies, it would be enough to have a father and a mother who mostly do not have same copies. But if father has versions G1 and G2, and mother has versions G3 and G4, the child can have any of (G1,G3), (G1,G4), (G2,G3), (G2,G4). So the features of the children are not predictable.
So plant breeders have invented this method, to use inbreeding to produce highly homozygous [2] lines first. Suppose (G1,G3) is the type you want. So first breed line A of plants which always have (G1,G1) and similarly for other genes. And breed line B which consistently have (G3,G3).
Now use A as father and B as mother, and voila, you can produce offspring that consistently have (G1,G3). So the offspring exhibit hybrid vigor, but are also predictable and similar to each other. Quality and consistency!
Now sell these seeds, everyone wants to buy highly productive consistent quality seeds. Profit!
But as long and you are the only possessor of the parent lines A and B, you are the only one who can produce this particular type of hybrid offspring. The customers only get the offspring, and you keep the lines A and B safe and secret.
If the customer tries to mate those (G1,G3) individuals with each other, they will get a mix of (G1,G1), (G1,G3) and (G3,G3), so the next generation will not be nearly as productive crop as the pure hybrid seed was.
So, the "vendor lock-in" is structured by not giving anyone else access to the parent lines A and B.
This is not intentional. Its how genes work. The seed on a plant depends on the pollinator. Just like fruit trees - you plant that seed from the apple you just ate, it won't grow more of those apples. It will grow whatever that apple was pollinated with.
This is true for many flowers and garden crops, it is not true for corn, soybeans, & similar.
The viability of hybrid offspring depends on the closeness of the parents. Lots of flowers can be bread from very diverse stock and the offspring are sterile, cash crop hybrids are not made from such diversity and are generally re-plantable.
Corn is generally carefully crossed as a last step in hybridization. The next generation will grow a plant almost completely dissimilar from the one being sold.
Its an issue trying to support farmers in developing countries. Our Romanian sister church didn't accept our corn hybrids. They had their own 'land race' seed they've been creating for generations, which works well on their difficult soil. If we sent them hybrids, they'd work for one season. And then they would be dependent on us for continuous shipments of seed each spring. We left them with their self-sufficient seed.
Hybrid seeds already did that 50 years ago.