The plow is a primitive method

2" wide plow compacts soil away from fabric, creating an open trench, allowing fabric to float out = haphazard installation and an installation that washes out easily
 
   
This plow is the same width top to bottom, resulting in horizontal soil compaction below the soil surface, and thus easy piping and washout. In many conditions soil is compacted away from the fabric deep in the slice, even though the surface appears to have fallen together or to be compacted adequately.