All of the workings that go on underground have been an intriguing subject since the first caveman dug his first hole. It’s a science in itself. As children we dug in the dirt. As adults we got bigger toys and continue to dig in the dirt. We make huge piles of dirt, move dirt, spread dirt, amend dirt and yes, we drive fence posts into it.
There are billions to hundreds of billions of soil microorganisms in a mere handful of a typical, pasture soil. That single handful might well contain thousands of different species of bacteria (most of whom have yet to be classified), hundreds of different species of fungi and protozoa, dozens of different species of nematodes plus a large assortment of various mites and other micro arthropods. Almost all of these countless soil organisms are not only beneficial, but essential to the life giving properties of soil.
Despite all of our technology and research that has been done on “dirt” we are still learning and gaining new revelations every day. But, the purpose of this short blog is to talk about what is going on underground with a fence post. The top few feet of soil does encounter a lot of changes and movement. It experiences both lack of moisture as well as an abundance of moisture. There is also freezing, thawing and heaving of soil. These simple facts make the life of a fence post somewhat variable and unpredictable.
Let’s look at the most common types of post materials that are normally used with high tensile electric fences.
Natural Wood Post: There are some native species of wood that are more rot resistant than others. Among the best are Hedge (Osage Orange) and Black Locust. These species, after 50 years in the ground will look better underground than they will above. They make a very good fence post and last generally a lifetime. They are environmentally safe and can be easily disposed of after they have outlived their usefulness.
Treated Wood Post: These posts are generally southern yellow pine but come in other varieties as well. The types of treatment have changed over the years and are still in transition. It is hard for the average consumer to determine which treatment is best. Technically, a CCA treated post should last 30 years +. But, we all know that sometimes some may rot and not last more than 10 years underground. The treatment chemicals used are sometimes environmentally questionable for obvious reasons.
Steel Posts: I always have to mention here that I feel strongly that steel is the enemy of electric fence, however there are lots of people that use them, so, I will write about them. They will last a relative long amount of time, unless you have alkaline or salty soils, in which case they will rust prematurely. Also, in coastal areas they will rust from salt water. The downside of using steel posts is the insulators that you have to use to insulate the post from the wire. Most insulators on the market are somewhat short lived and will create a potential for shorts and maintenance. As for their performance underground – it will depend on the amount of salts and moisture that ultimately promotes rust and failure. I am not aware of any environmental concerns with steel posts.
Fiberglass Posts: This is a non-conductive material and there are several types of fiberglass on the market. The ones that are manufactured as a fence post, have a coating that helps block the UV rays and aids in not allowing them to splinter. The other source of fiberglass is known as “sucker rods” and is a bi-product from the oil field and drilling industries. The sucker rods I see are a good long lived post. The problem with them is that they splinter and are hard to handle. Some people paint them with epoxy paint to solve that problem but it still can be a problem. Fiberglass is relatively flexible, but may shatter with extreme bends. As for underground – they seem to last a long time. Environmental issues could involve splintering and dust particles from sawing, drilling and handling.
Wood-plastic Composite Posts: The non-conductive PasturePro composite post is manufactured of polypropylene and wood fiber. This post is somewhat the new kid on the block. I was personally involved with installing the first ones around seven years ago. I have actually dug some of them up to inspect them underground and have to date not seen any deterioration below ground. In fact, my layman assumption is that they will likely last a very long time underground. You can read more about how they are made on this website. They do not have the same concerns about the dust and splintering that the older fiberglass technology has.
In summary, my personal recommendation for fence posts for electric fencing are: Natural native wood (if available) for Corners, Ends, Brace Posts, Gate Posts and Line Bosses. As a second choice, I would suggest a good quality CCA treated wood post. And for line posts, I highly recommend the PasturePro composite post. When I weigh up the entire pros and cons of every type of post – the ones recommended have more pluses and less minuses. I still maintain the idea that steel is an enemy of electric fencing and if you can keep it out of your system, you will be better off for it. And, lastly, the post that lasts the longest and requires the least amount of time with maintenance, repair or replacement is the winner. Oh, and by the way, we do put a 20 year warranty on the PasturePro post, both above and underground.