Alan Greer of the University of the West of England has written a particularly good contribution to the referendum debate in relation to agriculture for the Royal Society of Edinburgh: Agriculture, Food and Rural Policy. He covers a lot of ground in a relatively short space.
He notes that there is at least consensus about what the key issues are. Much of the debate reflects disagreement about whether or not the CAP is beneficial to the UK.
Looking at the views of the farmers, he says that the evidence is contradictory. However, the Farmers Weekly poll he refers to was based on self-selection rather than a sample. Supporters of Brexit are more likely to respond. I would place more reliance on the NFU poll.