hi
we had same problem but its resolv
you must dig with "tractor" at 20cm under surface all the track size, after you have 2 solutions:
1 you cover withe rocks
2 you cover with plastic "grillage" (like picture after)
http://www.wire-mesh-fences.com/phot..._mink_cage.jpg
you recover with ground again, pass the compressor roller and apply the astro
it's a little expensive but radical for a long time
sorry for my bad english dude
julien