Here is the chisel plow that I use to rip up the gardens in the fall/spring. I used the shanks from an old sears cultivator (SS16 tractor w/ implements) and welded them into a 1/4" wall section of pipe.
I can run this at about 6 to 8" deep depending on the soil conditions. I don't have my tires filled on the tractor, nor do I have wheel weights on it.
Usually I run it lengthwise down the garden in the spring, disc with a finish disc, then plant with the flex 71 planter. Then in the fall, I chop up all of the plants with the mower, and run this chisel plow at an angle (in late November). Follow up with an application of roundup if weeds/grass begin to grow again.