Don't mean to disparage at all what you have done so far. But perhaps to offer a different perspective.
The reason "tracked" vehicles work so well in rough terain is that they spread the load -and traction- over a much bigger area than wheeled vehicles could possibly approach. Generally thought of such machines tend towards Catapillar type -steel tracked- vehichles. But such vehicles are inherently heavy and require big high torque engines. Not necessarily best for a small farming environment.
May I offer instead the idea of the other type of tracked vehicles...
used on snowmobiles, snowcats and low impact logging applications. Such as the Jonsered "Iron horse" like so:
Before my health got in the way I was gathering parts and contriving plans to build my own tracked vehicle that would be rather a hybrid between an Iron horse and the bigger but slightly different snowcat vehicles. Using truly dirt cheap pneumatic HF wheels as boggies and narrow (5 inch wide) rubber conveyor belt material. Two strips wide on each side, connected with small metal channel, angle iron or even 1x2 wooden cleats forming the drive links as well as spreading the belt width. I bought the transaxle off an old massey fergusen garden tractor to provide for not only differential but 3 speed forward as well as reverse. (Actually a Peerless 1201 gearbox).
For engine I bought an electric start 13hp 390cc Chonda clone and a Chinese copy of a Comet type 40 torque converter. The Jonsered Iron horse uses a 9hp engine. Only things I was lacking was conveyor belt material and inside track wheel guides (bolt to inside track adjacent each outside cleat). I was going to build my own drive sprockets.
Advantages: CONSIDERABLY LIGHTER, quieter, and lower friction than steel catipillar tracks. Requires far less hp than a catipillar. Rugged and long life. (Converor belt material is used to convey rock and dirt... using it on top of rock and dirt essentually the same. I was going to use 4x 10 inch HF boggie wheels per side in close cantilever pairs, plus a single 13 inch HF wheel up front with drive sprocket at rear driven off transaxle. (Using hydraulic go kart disk brake rotors and surplus motorcylcle calipers for steering brakes.)
Just a few ideas for you. If you were located anywhere near me (SW Utah) I'd offer you a great deal on what I'd gathered so far... as I don't know if I will ever be in a position to use them myself now.