I grew up in Winnipeg. :-) Weeding and the like is considerably
less "back breaking" than most of the manual labour we have now (like house painting, window washing, road construction, etc). I've harvested rice by hand (cutting with a hand sickle). It's fun.
In North America, we build these huge farms because it's the only way to eke out a profit. You need serious capital to get started and you have a single person looking after land from one horizon to the other. This happens because the price of wheat is $4 and change a bushel.
And although milk production is often below cost, because of regulatory pressures distribution costs are kept low. Compared to wheat, milk is dramatically more difficult to process and distribute, and yet the markup is many times less. If you look at the difference, you can see where all the money is going.
I suggest that you can increase the cost of production of wheat 8-10 times without significantly affecting the final price. This would allow you to have 5 times as many farmers. It would allow them to use smaller, less expensive equipment. It would allow them to reduce their reliance on loans and insurance, further reducing their costs.
And, yes, we have more than enough labour as long as we pay people a reasonable wage. In my father's generation, university students all used to work on the farms for their summer jobs. Now? Pizza Pizza. The whole reason we have "summer vacation" is so that students could work on the farms.
I live in rural Japan now. I literally live smack dab in the middle of rice fields. Because of the protectionist policies for the last 60 years (installed by the Americans, BTW), farming here is dramatically different. A farm here can be about the size of a residential lot in North America. And... guess what? None of my neighbours use herbicide on their fields. 2 applications of pesticide a year (once in the spring for slugs/snails, once a few weeks before harvesting for grasshoppers -- some of the farmers have been growing an early variety lately and so are able to get the rice off the field before the grasshoppers emerge, so they skip the second application. Some skip the first application by over-planting and then thinning -- by hand!).
And for those interested, they do have amazing planters and harvesters. A couple of guys use traditional tractors, but they make an absolute mess of the fields. Most people use these tiny go-cart like devices. You can plant a field in less than an hour and it barely disturbs the soil at all. It's amazing. They have another device that cuts and bundles the rice stalks, but everybody hangs and dries their rice by hand. Then they load it up into pickup trucks and thresh it at a central location.
Is my hope that we can fix the distribution system, inject cash back into farms, reduce farm size and increase the number of people working on farms realistic? I seriously doubt it. But I still think that it's important to understand that this is a problem of our own making. This is about money, not about science.