Were they forced to join, did they sign up out of patriotism? Was it because of Religion? You'd think an army wouldn't want a bunch of farmers with no fighting experience in the front lines, nor would most farmers want to join the army and die.
I answered a similar question here:
I am a lesser noble in Western Europe circa ~1200, the King has just sent me orders to muster as many men as I can to join him on campaign, what do I do?