I would like to hear more about everyone's experience with the various air excavation devices now in use. Air spade, air digger, and others all claim to be the best. What is your experience with the various models available?

Thanks

Julian

Reply to post by Julian, on February 21, 2000 at 11:38:07:

Julian, you didnt mention the intended use. The tool's best use is not for excavating root systems, if that is your intention.
Although good for uncovering pipes, wires, etc. it is recommended that you not use it for a root excavation because it can really tear up feeder roots and does a heck of a job drying everything out. Not good. It does work for vertical mulching.

Reply to post by Michael Martorana, on February 21, 2000 at 11:38:07:

What is the applicability for excavation very near the trunk, to determine condition of or damage to main roots (the flare, collar, butress roots, compression roots whatever you like)? Fine absorbing roots seem of little concern there. With proper care can air tools be used without damaging the bigger roots?

Reply to post by Michael Martorana, on February 21, 2000 at 11:38:07:

Mike, Longwood Gardens transplanted two large trees. They were first bare-rooted, then lifted into place by helicopter. I was told they tried several methods of excavation,k including several with water and with air, and ended up mostly just hand excavating. Do have any knowledge of their work on that project?

Reply to post by Michael Martorana, on February 21, 2000 at 11:38:07:

I am not sure of any root excavation process that does not cause some damage to absorbing
roots given that the absorbing componant is often only a single cell or a mycorrhyza.

I have had troubles photographing them as they tended to be destroyed in minutes just
by being exposed to the atmosphere.

Mark

Reply to post by Russ Carlson, on February 22, 2000 at 05:52:10:

Russ, on Fri 2-18 there was an "in-service" meeting with Gary Johnson from the U of Minn, who is considered one of the people who has done extensive research on roots and the excavation thereof.
I sat next to Phil Gruszka, Head Arborist at Longwood. He seemed to be continuing his search for a better way to excavate root systems. They had used a pesticide sprayer loaded with H2O to excavate roots but I dont know about their use of an airspade. I do know that the IPM manager there is in complete agreement with Gary Johnson, The airspade can damage roots and its much easier, cleaner and cheaper to get down on hands and knees, excavating with some hand tools and a shop vac.
Johnson said most of his excavations took 20 mins with the longest at 2 hours. These diggings were to examine stem girdling roots and the depth of the dig was generally about 12" and extended about 18" from the trunk.
More is covered in his book, "A Practitioners Guide to Stem Girdling Roots."

Reply to post by Mike Martorana, on February 22, 2000 at 22:21:17:

Russ, Mike,

Call me a sceptic but how do you dig without cutting through roots. How does the
vacuum system go on heavy clay (like potters clay)

Lastly how does the air knife dry any more than the vacuum system. The majority of
small roots I understood were conductive, are covered in bark and as such are
underground branches. The most absorbtive parts, being young nerly forming roots,
root hairs (in reality single celled extensions) and mycorrhyzae. It has been my
experience that they all dry out in minutes when simply exposed to the air (although
it does get a little hotter here.). In any case the vacuum would cause more air to pass
by the root and therefore dry it out faster than just exposure itself?

Mark
Mark

Reply to post by Mark hartley, on February 23, 2000 at 06:42:22:

I've not personally used an airspade or similar excavation tool, but have used a vacuum to clear manually excavated soil. I think the majority of dessication is from exposure, as you suggest. Using a water stream to excavate with a vacuum to remove the slurry would probably reduce the drying effect, but only if the soil is replaced before the roots dry completely.

Any method of excavation, short of a Star Trek transporter, will cause some root damage, especially to the fine roots. Root hairs, mycorrhizae and some fine roots will all be dislodged as small clumps of soil are torn from the root mass, by any system. Air and water methods have the advantage of not causing mechanical damage tot he bark of larger roots however.

The vacuum only works with loose soil. It must have a low cohesion factor, or be loosened by other mechanical means such as air, water, or manually. Effectiveness will depend on the volume of air flow and the size/weight of the soil it is picking up (same as the machine you use for your carpets).

Reply to post by Mark hartley, on February 23, 2000 at 06:42:22:

Mark, I have little experience with an airspade but understand its principle. I do have experience with a vacuum.
The airspade uses an brutally intense pressure that literally cuts through soil, turf and can I understand fingers too. The vacuum is only a shop vac that clears debris after you excavate with hand tools.
So the tendancy to dry the soil, roots, etc with an airspade is likened to a high pressure pesticide sprayer being used to cut through the same. There is a pretty good possiblity for damage. The Vacuum, while is does move some air around isn't nearly as invasive.

Mike M

Reply to post by Julian, on February 21, 2000 at 11:38:07:

Have a look at www.terravent.com. This does the work without injecting cracked oils into the soil.

Reply to post by Michael Martorana, on February 21, 2000 at 11:38:07:

I have been following up on using compressed air tools for excavation around tree roots. I have interesting reports, many pictures, and proffesional contacts for anyone interested. They could better describe results in an arboreal professionalism than I could.

I work for MBW who makes the Soil Pick.

andym@mbw.com