Manure.

If you have decent soil depth, you don't need to do anything.  Where you don't, you can do what the other ks guy said by pushing top soil off then bringing it back.  Adds about 50% of the time to the construction but i suppose a better dozer operator could do it much quicker.  

Usually, we just cut them in, then work the heck out of them in the spring so you get a little soil movement into the channel the first few years plus a little extra nutrient movement and you are off and running.