Protecting fencing from garden soil

I didn't know where to post this but I'm looking for suggestions to help protect a wooden fence from rotting due to garden soil touching it. I have a border that surrounds our back yard and we are going to be replacing a lot of our fence this year because the soil has been touching the panels and posts. I rake it back off the fence often but rain and watering just make in migrate back again.

 

Large flat rocks or prefab cement pieces with landscape fabric between them and the soil

 

Another common option especially with cedar panel fencing is to install the fence so that the bottom of the main fence panel structure is a few inches above the soil height. You can then add replacable 2x8" pressure treated barrier boards beneath the fence itself. Stake them so they stay vertical. These will help keep weeds and animals out of the yard while protecting the fence itself from rot and dirt. These boards will be partly buried in the ground so they will rot eventually, but can be quite easily an economically replaced without the need to remove fence posts etc. Alternately you could leave the fence bottom close to the nominal grade and add similar barrier boards on the inside side of the fence with small cleats on the back to provide an air gap between them and the bottom fence board. In this case you would likely not need to stake them. If your fence is of the picket type the second option might work better as it would still preserve the clean, vertical picket look on one side of the fence. You could also use 4x4 to create a back wall for your beds and locate it so the outside of the 4x4 rests against the inside of your fence posts. That way when the soil slumps down it will rest against the 4x4 not the fence panel. Being thicker, the 4x4 will take quite a long time to rot