The National Farmers' Union has published an evaluation of the arguments for and against UK membership of the EU from a farming perspective. At this stage they are not taking a 'better in' or 'better out' position ahead of the outcome of David Cameron's negotiations. However, this is really a holding position so that they can maximise their influence and it is difficult to believe that they would eventually recommend withdrawal.
You can read the report here: NFU Report
Agra Europe has produced an analysis of the NFU report, emphasising that it shows the way in which the CAP has become less common: An internal market?
The 'Brexit' committee I am chairing for the Farmer-Scientist Network of the Yorkshire Agricultural Society has now produced a draft first report which will be considered at a meeting in York next Friday.