Having this discussion made me doubt myself so I called my insurance agent, she called the company and:
I spoke to an Underwriter named Lisa, at ASI and explained about the tractors and mowing and sometimes having to go on the road.** Lisa said, as long as the tractors were used to maintain The yard there would liability coverage.
Well, I got lucky, since yes, it might be a big "yard" but that's what I'm doing, maintaining my property. So my homeowners covers me, as I thought, for my run around the block.
In a year, when my tractor is paid off and the Kubota coverage falls off, I will likely increase homeowner contents coverage a little. I already have replacement cost on contents, which gives me 70% of the dwelling limit, and thankfully there is no coinsurance on contents. A tractor, or any tractor implement, is plain contents unless excluded or limited. Which tractors aren't...unless used for business.
Coinsurance is important, if you have a 100K homeowner limit, 50K on contents, and someone steals your $45k tractor, the insurance will pay for the whole thing. Doesn't matter if you are underinsured for total contents, they will pay up to the policy limit. There isn't a penalty clause on contents like there is on building coverage, in order to qualify for replacement cost coverage.
There is a term called PML for claims, meaning probable maximum loss. It's a determination as to how much of the total insured property could burn up or blow away at any one time.
Since most tractors are out in the barn, usually they won't burn up with the house and vice versa. Now a direct hit by a tornado or a plane, then you can pay policy limits. So when you chose a contents coverage level, either standard or increased, keep in mind the likelihood of losing everything you own in one occurrence. If you live in tornado alley, california brushfire area, along the ocean, I'd buy as much coverage as they will give you that makes sense in your budget. Rarely does anyone complain about having too much coverage in a serious loss.
So all of this is to say your homeowners policy contents will cover your tractor to whatever degree of coverage your policy provides, usually either broad form or all risks, based on either ACV (depreciated market value) or Replacement Cost, (claim paid without depreciation). Homeowner liability you need to check on yourself, make the call. Either way, for non business use, coverage should not be expensive.