Aerating and Inoculating for Health

[treeseer]

Here's an infomercial for the wrecking bar and the Aqua-Cannon:

 

[ScottF]

Is there any evidence that this works?

[David Humphries]

How can you be sure you're not inflicting cambial damage to any unforeseen roots, with the 'wrecking bar' ?

 

What would be the span between each hole ? 20-30 cm's ?

 

5 for 100 = 5 individual holes for $100 ?

 

 

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[treeseer]

We avoid damage to any unforeseen roots, with the 'wrecking bar' by wiggling it first, and thrusting cautiously, at varying angles. (insert bawdy reference) Traditional tools for deep aeration include 2" augers. The bar is much less damaging!

 

The span between each hole depends on root architecture and soil type, but yes 20-30 cm's is good, closer not needed.

 

5 for 100 = 5 Aqua-Cannons for $100 at our state fair, and at big box stores here. The tool is a joke; the process of penetrating subsoil is the message. But I like your thinking re $20/hole!

 

Scott, what would you suggest, when drainage must be improved? I've seen roots growing downward into aeration holes so yes it works to deepen the rootzone.

[ScottF]

Drainage into what? I'm not sure I follow. Soil compaction generally occurs in the top of the soil horizon, 100-150MM (I remember my soils professor demonstrating this by taking a column of soil in a cylinder and applying pressure- it's easy enough to compact the top of the column, but increasingly difficult as you move down the column as the load is spread into a cumulatively greater volume of pores. The exception to this would be wehn, for instance, you have repeated heavy vehicle traffic over a clay or otherwise unstructured soil, where ruts develop and you end up with deep and stubborn compaction and effective destruction of the topsoil structure.

 

I'd suggest that if you punched holes into any soil and introduced a more porous (relative to the adjacent soil) material, then you'd create a density gradient that the roots would necessarily move into (the path of least resistance). Whether this is evidence of some sort of net beneficial effect, when the possible checking effect of damaging roots is considered, I don't know.

 

Is there any evidence that "deepening the rootzone" is necessarily beneficial either? How would you know that a tree had a "shallow rootzone", and is this a tree defect to be corrected?

[treeseer]

Scott, compacted soil layers also exist, naturally and through previous mechanical activity, well below the surface; see 'hardpan'.

 

As with planting holes, gradients are mitigated by fracturing the soil beyond the hole, by moving the bar sideways. Less interfaces, more mixing, better results.

 

Of course the closer to the trunk this is done, the more care is needed to avoid root damage. Not difficult really. The video showed this work very close to the trunk; not typical sorry.

 

The evidence of benefit is seen when water drains more readily from a site.

Edited March 10, 2014 by treeseer

[ScottF]

OK, subsurface hardpan would normally be down to repeated ploughing (generally in an agricultural context) and it would cut under the top horizon and compact the lower. Most hardpans caused by anything other than chronic tillage (more likely in an urban forestry context) are in the top of the soil. When I think of a tree that's suffering from compaction, I would normally be considering a tree that's begun life in a reasonably porous soil (which has allowed it to get to tree-size- this would not be likely in a tree growing with a relatively deep hardpan) which has become more and more trafficked by people, mowing, car parking etc, compacting the top of the soil and which has gradually affected the tree's vitality. Given the size of this device, I'm guessing it would only penetrate a "surface" hardpan anyway?

 

I can imagine that, like radial tranching or similar, this would have some sort of benefical effect provided the lower, uncompacted soil (and ideally subsoil) was permeable (i.e. the water had somewhere to drain to). How many holes do you typically have to make to have a commercially-useful effect for, let's say a 600mm dbh largish garden tree, and how long would it take to do?

 

You mention inoculation in your post. Are you referring to the effect of Guy putting in the healthy roots from another tree with gravel, or some sort of commercial mycorrhizzal product? The jury still seems to be out over here about mycorhyizzal inoculants on established trees (although I can imagine the benefits of container-grown nursery stock), but is it established practice in the US?

[treeseer]

"Most hardpans caused by anything other than chronic tillage (more likely in an urban forestry context) are in the top of the soil."

 

I'm no expert on British soil, but here the C layer, >1'-2' deep, is very often poorly draining clay.

 

" Given the size of this device, I'm guessing it would only penetrate a "surface" hardpan anyway? "

The bar is 5' long, and often goes halfway in.

 

" How many holes do you typically have to make to have a commercially-useful effect for, let's say a 600mm dbh largish garden tree, and how long would it take to do?"

 

Highly variable depending on several factors. For a big job I'd use the Air Knife x-hfa.

 

"You mention inoculation in your post. Are you referring to the effect of Guy putting in the healthy roots from another tree with gravel, or some sort of commercial mycorrhizzal product?"

 

Mostly rely on fresh roots and soil. Niot a Guy thing; check research by Ferrini and Fini (honest). I do often add a commercial product as well. Studies were based on stale material, or soil that already had good microbial balance. The research here is strongly tilted toward chemical usage. They go out of their way to set up studies that dis alternatives.

 

Nonetheless, inoculation is indeed established practice in the US. Unfortunately 'fell and replant' is common advice here as well, when consultants and arborists avoid getting their hands dirty.

Edited March 10, 2014 by treeseer

[ScottF]

If you've ever looked at a geological map of the UK you'd see we have every imaginable soil type, sometimes acutely different geotypes right next to each other. Great fun.

 

In terms of the time thing I was just thinking of the cost vs benefit angle. I would imagine this would come into it's own where you did have, for instance, truck ruts on one side of an RPA in dry clay where an airspade would struggle and where the tradeoff of possible root damage ve relieving severe compaction would be acceptable.

 

The appoach of using a nearby healthy tree's roots an an inoculant seems really sensible- it should have the right balance of species and site-specific mycorhizzae/bacteria etc. Makes more sense than a generic mix of lab-cultured taxa in suspension to me.

 

"The research here is strongly tilted toward chemical usage. They go out of their way to set up studies that dis alternatives".

 

As with everything

 

"Nonetheless, inoculation is indeed established practice in the US. Unfortunately 'fell and replant' is common advice here as well, when consultants and arborists avoid getting their hands dirty."

 

I'm always happy to try something that's likely to have a beneficial effect. I would suggest (maybe wrongly, I don't know), that people is the States are willing to spend a bit more on their trees. The cost has to be very clearly reflected in any benefits here.

[treeseer]

sounds good Scott. The readiness to open the wallet varies a lot, but good info can open it more readily, in any land. Raising the bar for proof of great benefits too high inhibits experimentation tho; the benefit when drainage and aeration are improved seems obvious to me, and suffices for many clients, who know that proactive is cheaper than reactive treatments.