Four drawings illustrating the correct spacing and depth and the incorrect spacing and depth. The two drawings to the left show the correct spacing (top) and incorrect spacing - too wide(bottom). In the top left image the text reads from left to right with arrows pointing at each item:  Loosened soil, Ground, Correct Spacing (30 to 42 inches typically), Subsoiler shanks, Compacted layer. The bottom left image has a similar layout with arrows and text reading left to right: Loosened soil, Ground, Incorrect Spacing – too wide, Compacted layer still in place, Subsoiler shanks, Compacted layer.  

The drawings to the right show the correct depth (top) and incorrect depth (bottom).  In the top image the text reads clockwise from bottom left corner with arrows pointing at each item: Loosened soil, 12 to 22 inches deep, Ground, Correct Depth, Subsoiler shank, Compacted layer, 1 to 2 inches below the compacted layer.  The bottom image is similar with arrow as well and text reading clockwise from lower left: Compacted layer, 12 to 22 inches deep, Ground, Incorrect depth – too deep, Subsoiler shank, Loosened soil, Compaction increased, More than 2 inches below the compacted layer. 

Images are not to scale.