It is significant that jury is made up of farmers because they are fair minded.
Step-by-step explanation:
Jury is made of the farmers and it is significant to have such a jury made up of the farmers. This jury has been formed because it is said that the farmers are mostly fair minded.
So having and being fair minded, farmers will give the decisions which will be fair and just for all the people and not biased towards any one. That is why Atticus always put a Cunningham on the jury.