Posthole Digger Post Hole Digger - Auger Size?

[BRIGUY]

This spring I purchased a WorkSaver model 300 PHD with 6" auger. My plan was to use it to set 4x4 posts in concrete. I very quickly found out that this wasn't the way to go. A PHD is not a drill press and will wander if it encounters any thing (root,rock etc) Keep in mind that it will take some practice the dig a straight hole even under ideal conditions. So I ended up purchasing a 9" auger from my dealer (biggest one in stock at the time). WOW!!!! what a difference I was putting up 400' of 6x8 wood dog ear fence, setting all the posts first then hanging the fence after. The 9" worked good for me, but almost half of the holes still needed a little work with a bar and shovel (roots and rocks) to get the spacing correct and to keep them in a straight line.

I agree with the other posters for 4x4 posts 9" is the smallest I would go with. bigger will not hurt a thing. back filling is a snap, the fill is right there. As far as tamping I think it would be easier in the larger hole.

Now I have a 6" auger that I may never use.

 

[fractal]

I bought my post hole digger a year and a bit ago. The dealer told me it did not come with an auger and asked me what size I wanted. I told him I was going to plant metal fence poles and 4x4's. He sold me a 9 inch auger.

I can get the 4x4's square with the hole the 9 inch auger makes (barely) with some manual cleaning. I would not want to try with a smaller auger without a lot more practice. My tractor is about the same size as yours so you are likely to run into the same issues with the angle of entry changing as the bit goes down.

 

[Gatorboy]

<font color="blue"> I dig mine as far down as the auger will go, then I mix in compost with the spoils that the auger throws out of the hole. I refill the bottom of the hole up to the level of where the tree or bush should be planted. </font>

I believe it is best to leave the ground at the bottom of the root ball undisturbed. Therefore, I would dig down to the required depth, rather than digging deeper and then filling it back up with compost mix.

 

[KiotiJohn]

</font><font color="blue" class="small">( I believe it is best to leave the ground at the bottom of the root ball undisturbed. Therefore, I would dig down to the required depth, rather than digging deeper and then filling it back up with compost mix. )</font>
I've been doing a lot of reading on this line and our local ag extension office recommends not enriching the soil in the planting hole because the roots want to stay in the better soil/compost rather than get deeper. However, they do recommend disturbing the dirt below to promote easier root expansion, but replacing with the same soil sans the compost. John

 

[Bob_Skurka]

<font color="red"> I dig mine as far down as the auger will go, then I mix in compost with the spoils that the auger throws out of the hole. I refill the bottom of the hole up to the level of where the tree or bush should be planted.
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I believe it is best to leave the ground at the bottom of the root ball undisturbed. Therefore, I would dig down to the required depth, rather than digging deeper and then filling it back up with compost mix.
</font>

Yup, I've heard that I do it wrong, but in my concrete like clay, I do it this way and have had very good success with it. Some plants, like oaks, have a tap root that goes down, others, like maples, have surface roots. The tap root type plants have a heck of a time getting into our soil, and we've planted and lost all sorts of trees/bushes that died. We've started digging really deep about 4 or 5 years ago and every tree that we've planted that way has faired better. Maybe it is a clay soil issue? I really don't know, but I got tired of pulling up dead trees that I had planted only one or 2 years earlier.

My biggest problem is that I have to compact the soil mixture that I put back into the hole. If I don't compact it, the trees/bushes will sink into the hole! I learned that lesson the hard way /forums/images/graemlins/frown.gif

 

[meledward23]

Okay Gentlemen,

Tree Planting Lesson One:

My Qualifications – BS Horticulture, many BS certifications that mean squat, and about 4000+ trees per year planted under my watch for the last eight years.

Conditions – Clay, Construction Sites (In other words hard compacted clay with little organic material around)


Issue One : Hole Depth
The main hole should be the depth at which you want the tree. Dig a smaller hole at the center (doesn’t really need to be centered) of the big hole. A post hole digger or small auger should work great. This hole is to create a drain out of the planting pit. IT is required to go through the hardpan. Sometimes an additional 5 feet down from the 3-4 that we typically dig, other times only another foot, and at other times the tree hole already achieves this mission.
The small hole/drain is required because you have disturbed the a section of hard clay soil amongst other clay soils. When you backfill around this tree(or whatever) you are packing in a softer dirt. Even if it is the original you will not pack it back in as tight. You now have a porous zone around your tree. That’s good till water takes up all the air gaps. This happens when water fills the whole (it the softest place around) and has nowhere to go. Called the very scientific term “Bathtub effect”. A little hole in the bottom should fix this. We backfill the little hole with soft dirt. It doesn’t need to last for years. As the soil you backfilled hardens and the tree roots branch out things will balance back out.

Issue Two: Backfill
What to use? Why what you took out of the hole of course. If you amend to much, or put a porous black dirt back in then you are creating a major “bathtub” again. That’s not good. The original soil will eventually harden back up. Initialy roots will push out into the backfill. As it hardens then the soil surrounding the planting pit doesn’t look so bad.

Issue Three: But I want to Amend, I have so much compost:
The go up! Build a compost layer above the clay soil line. This is a called a raised bed. On a large scale a berm. This is the way to go. DO NOT till a level surface in a clay environment put 4” of humus down and till it in. You have just created a giant bathtub. Instead work the soil levels up.

Many will debate this for years to come. Ag extensions, Professors, Professionals. All I can say is that we install more than a few thousand trees per year and lose less than a few dozen and those dead typically are because it’s the wrong tree in the wrong place.

 

[Bob_Skurka]

Matthew, thanks. I guess I am doing it 1/2 right & 1/2 wrong. Digging down as deep as I can get is the good thing, filling the hole with about 1/3 compost and 2/3 spoils from the hole is the part I should not be doing. I did stumble on the "bathtub" effect all by myself. When I did with a PHD for the purpose of planting, I also always break up the sides of the hole so the roots don't get "pot bound" inside the hole. . . at least that is my theory.

 

[akoliver]

Good Info guys! I was going to start a thread on this same subject...
Anyway, What is the largest auger a Kubota 2710 can handle.
I want to put some bigger trees in (20gal), and the soil is mostly good, although I expect to run into clay and some rock no mater what size auger I use.
Also, what is the trick to using an auger with a small tractor. Several buds have warned me against the whole project. I've never tried it, but it certainly can't be that hard... What am I missing?
Thanks,
Ken

 

[To20Chris]

I have a TSC PHD with a 9" auger - put in about 120 posts last year. I like the smaller auger because on the holes that go well (no rocks!), I can make a clean hole, with the minimum undisturbed soil around it. There's still enough room to back fill it, and it's strong as soon as you tamp it a bit. 9" is a little small for the bigger coner posts, but you can shave them by hand, no big deal.

Mark the spot with a can of upside down spray marker paint (Home Depot, etc.). Drive over the spot until you can drop the auger point (with the PTO off) onto your mark. Once the point is stuck into the ground a little, then move backward or forward until the auger is vertical. You may have to "bias" it at the top of the hole, because the angle will change as the 3ph arms drop - you'll get used to this! Engage the PTO and drop it slowly. If you find it is walking, you can inch the tractor (within reason) to re-direct it.

As you are pulling it up, remember that the auger will want to flop all around once it clears the hole, so go slow at the top.

Run the PHD as slow as your tractor can run it, speed will not help you and makes for more busted shear bolts.

If you have rocks/stones, try "pecking" at it, sometimes that helps pull them out of the walls and into the hole.

If you know you've knocked a rock into the hole, pull the auger a out and and get the rock out. PHD can't break up rocks very well, you just break the shear bolt and curse a lot.

You'll still have to pull the dirt out with a hand post hole digger, so get a good one.

Throw away that **** handle that comes with it, unless you have someone to help - then put it on backwards so they'll have something to do. Make sure your helper is not too bright, else they may not agree to do this.

Oh yeah - I put those posts in with the old Ferguson - no live PTO, no live hydraulics. Sure wish I had had Kioti for that project!

 

[fishman]

My 2910 is rated for a max 12" auger size. I suspect your 2710 is similar. I have no shortage of power at all and I doubt you'll have a problem either. /forums/images/graemlins/smile.gif

Lots of people on this site have used their phd for planting trees. You should have no problem unless the ground is really rocky.

I run my auger at between 1000 and 1500 rpm. That's how most folks recommended to do it and it works very well. Any faster and the auger can screw itself into the ground in a blink of an eye, making for a bit of digging to get it out. It also vibrates a lot more at high speed. Let your 3 pt hitch down a little at a time to let the auger clear the hole. If you drop it all at once, you'll have a stuck auger. /forums/images/graemlins/frown.gif

To keep it straight, you may have to move your tractor forward slightly as the auger digs. That happens because the angle of attack changes as the 3pt drops and the top of the auger gets angled back.

Whatever you do, don't let anyone stand around by the auger as you dig. There are plenty of deaths and injuries reported every year from using post hole diggers. Be real careful.

I dug a few practice holes when I first got mine and after that things went really smooth.