To answer the question directly: No. You can get Cat6 rated for outdoor and burial use which doesn't require conduit.
However, I strongly advise that you do not bury 1000 feet of cable.
Let's break this project down.
First you need to dig 1000 feet of tenching. Hopefully your land is such that you can rent a bobcat trencher for this task. Without machinery this week be a huge amount of work. Assuming you have a trailer this equipment rental should be under $350 per day. If you have easy access to diesel a novice operator could trench 1000 feet in a day. Dig it deep, 18" minimum. Also you'll want an attachment to fill the trench back in. This will be another day rental. Equipment total ~ $700
Next, this is a capital investment in your property to be able to interconnect to the road. If you're going to do this you should not only run conduit but you should run two of them. Why two? Because you are likely not allowed to run high and low voltage in the same conduit. Even if you're allowed to you shouldn't due to interference, electrical risk, and generally the savings just isn't big considering the scope of the project.
In this quantity you should be able to find 3/4" conduit for about $0.21 per foot, probably in 20' sticks. This means you will be buying at least 100 sticks. $2100. Ouch. You could go smaller on conduit but the savings may not be worth it to you.
You need to use appropriately rated cable even in conduit because the conduit can and does fill with water.
1000' of direct burial cat6 should be around $170.
But, ya know, big sections of cabling like this tend to come into service boxes along the way. This is to simplify pulling, repair, troubleshooting, installing repeaters (which are necessary if this is Ethernet), and similar.
If I were you I'd come into a service box every 200' in this run, whether you use conduit or not. There are many options, but let's say $50/box (more if you need them to survive snow and sun) so that's 4 boxes assuming one end is the house and the other already has a Telco box, but the ISP won't let you bring your own conduit into it. $200
I see the hesitation on conduit, given the $2100 price tag versus the $1070 other stuff. But remember that this is double the conduit... Only one is half that: $1050.
What does the conduit buy you?
It protects the cables better and gives you more options (possibly including a better fiber!). Mostly though, a buried cat6 of this length is almost certain to become damaged... Without conduit a damaged cable likely means retrench and redo the entire run, as you won't have a way to localize damage and, should you try digging it up to find damage you'll probably damage it in the process.