What kind of load are we talking about?
We covered ground anchors on the NPTC recovery course and used a number of solutions depending on the load including the plough described above, multiple metal stakes chained together (500mm long and 25mm angle), buried tyres, and various metal plates with shackles attached. All worked well until they didn't. They all relied on being able to dig and bury or drive something into the ground.
For the big 'screw' types you can get driver tools that give you a good mechanical advantage when trying to get them into tough ground - think large tommy bar.
I confess, I've never enjoyed using a plough type anchor. If the ground is soft enough for it to dig in, it's soft enough for it to pull out. Although the angle of load is designed to force it down, it doesn't always work if there are roots or stones in the soil. They worked well in the desert though.
The problem Pattree described earlier is the monumental difference in static vs dynamic loads that you can get when dragging stuff along the ground. In forestry/woodland work we can reduce that risk considerably by using a winching cone on the front of the load and that also reduces how strong an anchor you can get away with.
Probably a lot of grandmas and eggs there - sorry
