The tillers of the earth
are the ploughmen, and they are called to be ashamed because the harvest has failed. This expression is based on comparing the harvest with someone who has not achieved his goal and is therefore ashamed and disappointed with his expectations. They withdraw from the people in shame, because the people expected them to produce something for them to eat.1
11 Be ashamed, O tillers of the soil; wail, O vinedressers, for the wheat and the barley, because the harvest of the field has perished.