No, farmers should not do another job along with farming, because it is a full-time job. Farmers are up very early to begin their work, and they work very late. Farmers already work enough, they do not have time to do another job. They do not need second jobs any more than anyone else does.
Many farmers live off of farming primarily or even solely. Sometimes this is very profitable. They should have the choice of whether they want to continue farming solely or to have another job. The future of farming may be unclear so it may be wise to take another job, but that doesn't mean they should be pressured to.