You need to fill your tires so the water covers the rim (75% full)thus keepin oxygen away from the metal. NAPA has the fitting to just put it on your garden hose. You need to block up your tractor tire so you dont unseat the bead. After its blocked up, unscrew the top half of your tractors valve stem to remove all the air till zero pressure. Hook on your NAPA filler after selecting the right adapter to fit your tire (it will come with 2 or 3 different types. You will need to vent air as it is filled. Turn off the hose and push the air vent button to remove the air, then turn on the hose again. You can tell when it gets full by the sound of the water running in the tire. Just like spraying a hose in a bucket then sticking the nozzle under the water. As soon as it changes tone, cut off the water, remove the adapter and let any excess water out till you start getting water and air comeint out, then you can screw in the top half of the valve stem. Plain water should work for you especially if you keep your tractor in a garage. If parked outside, park it where the sun can hit the tires and warm the water during the day and it will take several days of below freezing conditions to cause the tire to freeze up. Freezing up wont hurt your tires as long as you dont move the tractor when they are frozen AND you dont overfill the tires with water. The Air pocket above the top of the rim is necessary for smoothing the ride because water dont compress so you need the air pocket so the tire will give a bit when operating and in case it freezes, this allows for expansion. I grew up in North Louisiana and we had plain water in all the tires. They did freeze when we had the occassional hard freeze for days but just let it set till the tire quiets sweating (like an ice tea glass in the summer) When it stops sweating, the tire is ok to move.
OR if you want full winter time use, fill it with 30% Methanol and water mixture for -20F protection. You will need a pump for this operation.