That's exactly why the number of farmers keeps reducing under capitalism. In socialism, you can get to democratically decide how much people are paid depending on the actual needs of the economy.
No, mate, I'm obviously not suggesting a return to feudalism. I'm suggesting that if humanity needs more people allocated in agriculture, it should allocate more people in agriculture.
Allocate doesn't have to be through violence, it can be through incentive. If farmers made twice as much as stock traders and worked 30h a week there would be plenty more.