Even in fences where the line posts are set in compacted earth, the end posts and gate posts are often set in concrete. Some fences set every post in concrete. As a result, taking down a fence or replacing individual posts often involves pulling out the cement plug in the post hole. Since this cement plug was poured to make the post more rigid, removing it is no easy task and involves considerable manual labour.
Dig up the dirt covering the top of the cement plug, clearing a bowl-shaped area above the plug.
Insert the blade end of the iron tamping rod between the plug and the surrounding dirt, and push the rod down as far as you can. Then push with your legs and use your body weight to pry the plug away from the dirt. Repeat at least once more on the opposite side, but you may need to do this three or four times around the circumference of the cement plug.
Squat near the fence post, grasp it firmly with both hands, and pull it and the cement plug up by standing, which puts your leg muscles to work. In the case of a big cement plug, this might not be enough.
Clamp the fence post to a post-puller, or chain it to a winch or to a small utility vehicle like a Bobcat if. Pull the post out. The winch or post-puller may be mechanical and require you to work a cranking lever.
If you need to remove multiple cement fence plugs, you may wish to skip trying to uproot the plug by hand, and go directly to the use of a mechanical aid like a post-puller or Bobcat. If you do not have a winch, post-puller or Bobcat handy and cannot rent one, remove stubborn cement post plugs by digging out the dirt surrounding the cement plug. You may need to dig all the way down to the bottom to ultimately free the plug, but this eliminates the need for additional machinery. Some truly stubborn cement plugs might not come out even with a mechanical aid like a Bobcat or post-puller. In these cases, either dig out the cement plug and try again, or break up the cement plug using a jackhammer and try again.
Pulling too hard on a stubborn cement plug with a Bobcat, winch or post-puller might snap a wood fence post or bend a mental one, which will make additional removal attempts more difficult. If the cement plug won't uproot, do not keep pulling on it. Instead, loosen the cement plug through digging or jackhammering (as described above), and then try again. Use caution or additional helpers to avoid injury to your back.