Ground cover- 5 acres
Hello, I am OSU alumni, and use this website often, it is a wealth of information! I'm wondering what a good ground cover(s) species would be suitable and affordable for ~2.5 acres of field space in Western Oregon. My hope is to subdue some of the blackerry bushes, and competitively wipe them out over time with cutting and suppression of new growth.
Apologies for my delayed reply. This resource is excellent for choosing cover crops for different niches in annual crop rotations: http://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition. You can download it for free.
In your situation I would probably cut down the blackberries, rip the soil below ground (i.e. chisel plough, sub-soiler or heavy disc) to break up roots as much as possible, then plant a vigorous over-wintering cover crop this fall like cereal rye (60-80lbs/ac) and common vetch (40-60 lbs/ac) as soon as possible - by early October.
If you start to see blackberry regrowth in the spring, I would kill the cover crop and repeatedly disc and chisel plow the blackberries in late spring/early summer. Then in mid July you could plant Sudan grass (or Sudex). It is very competitive, and will winter kill after the first hard frost in the fall. Then it leaves a mulch on the soil over that winter, and would be fairly easy to work in the following spring so you can plant whatever it is you want to establish then.
You can speed up the process using herbicides if desired. I don't deal with that often, so would refer you to this publication: http://pnwhandbooks.org/weed/
I hope this helps.