Since you live in NOVA, just know that everything is taxed!! In all seriousness though, it depends which county you are in and if you set yourself up as a farm etc... The county I am in does tax them.
I have been a Property Claim Manager for quite a while in VA. I can answer the insurance question fairly well as all of the policies closely resemble each other as they have to meet the state guidelines and acceptance. If you look at your policy under the "Property We Do Not Cover Under Personal Property" section, it will state Motorized land vehicles.........unless used soley for the service of the residence premises......
That is a little paraphrased, but the exclusion is intended to not cover any motorized land vehicles ecept those that fit in to that category. So, if your tractor is used solely on your property and not taken any where else to do anything, there should be coverage as applicable to the terms and conditions of the policy. I'll give you a bummer example so that you'll have an idea when it wouldn't be covered. You go down the road to mow a friends field and the tractor catches on fire. The first question is where did it happen? Then the next question is why was it there? Then the bad news. It wasn't being used solely to service your resdence premises if it was down the road working.
And before anyone says , "well my agent said", I'll clarify again, I don't sell the policy but I do ensure that it is applied correctly.