I think normal farm policies do not cover drones....nor a few other things you might be thinking are covered.

But anyway, you might consider a "per occasion" insurance for drones. If you're flying over the middle of your farm with no people within miles, then do you need any extra insurance? But, if you're going to be flying legally where there are more people or machinery, or a lot of buildings (think towns), then I'd consider the per occasion insurance. It's been around for a few years now. Set up an app on your phone, choose your liability coverage, choose a start/end time & you're covered. Again, it's up to you to operate legally. Whether you're covered or not if illegal, I don't know. Are you covered if you were clocked at 80 mph just prior to hitting the deer and injuring your passenger? 

The insurance is called "Verifly". Here's their website. I have paid for their policies, but have never had to test their coverage. Though I have read that it gets good marks from insurance industry reviewers.

https://www.global-aero.com/programs/thimble-verifly-app-drone-insurance/