When my wife was a kid, her mum took her and her siblings to the local farms to pick fruit, spuds etc during school holidays, as did many of the other local families.
When my kids were young, my wife took them with her and did the same thing. When I was on short time at work I joined them, picking spuds for the local farmers.
As someone mentioned, travellers (they hadn't sunk to being pikeys then) would regularily turn up and do the work for some cash.
This worked well enough for the farmers for god knows how long, until they suddenly had a never ending supply of very cheap labour queuing up to work for them.
I don't believe for one minute they will go broke without this. They are well known for being the greediest of greedy businessmen.
I well remember a local multi millionaire farmer, sat in his brand new range rover, telling me that if he didn't get another few acres of spuds harvested in the next couple of days he would go bankrupt.
I told him he was talking utter bollix, he went slightly red in the face, laughed, and then drove off.
They are angling for enormous post Brexit subsidies. If they are too greedy and price their goods too high, people will vote with their wallets / purses and buy imported produce instead, and that is how markets should work.