This is from the NYT, about a farmer who tried to hire American workers rather than illegal immigrants:
Six hours was enough, between the 6 a.m. start time and noon lunch break, for the first wave of local workers to quit. Some simply never came back and gave no reason. Twenty-five of them said specifically, according to farm records, that the work was too hard. On the Harold farm, pickers walk the rows alongside a huge harvest vehicle called a mule train, plucking ears of corn and handing them up to workers on the mule who box them and lift the crates, each weighing 45 to 50 pounds.
The article is interesting throughout. See also Alex’s earlier post, for some added interpretation.