Arborists, fertilizing trees & shrubs with
tablets, please advise me on the type of auger
you use. I question if a hand auger will do
the job, especially in hard, compact clay
soil. Naturally a power auger is more
expensive, but may be the overall best
investment. Please share your experience.
Thanks

Reply to post by Olen J Sharron, on March 11, 2000 at 09:37:10:

If the radius from trunk to drip line is 20ft you have 1256sqft to drill holes every two feet.

Or roughly 1200 sqft if you start 4ft from the trunk, you space the holes 2ft 12-15in deep (UWEx "Urban phytonarian A2308" Hasselkuss/Schulte) apart I figure 300 holes if you don't extend past the dripline.

How many properties will you do in a year?

Next question is would a small pumping system for liquid soil injection be more cost effective than the gas-auger?

Reply to post by Olen J Sharron, on March 11, 2000 at 09:37:10:

Nobody in the tree-care business wants to hear it, but the research indicates that surface application of fertilizer is just as effective as subsurface application. I am convinced that we promote "deep-root" fert simply because our industry has equipment others do not have. Augering holes may aerate the soil, but it is a very temporary phenomenon unless the holes are filled with a non-compactable material. Where are the roots? If nitrogen is placed below the roots, it may do nothing but pollute.

Reply to post by Ed Milhous, on March 11, 2000 at 09:37:10:

Not only do we aerate, but we also open up channels for water to penetrate when we irrigate during our annual drought. I always recommend mixing half granular fertilizer and half humus or perlite. Also it is difficult to broadcast fertilize trees in a lawn area unless you fert the entire lawn, which people do on a regular basis anyway. Of course we all know that trees and lawns are not compatible(?!)
very treely,
lew

Reply to post by lewbloch, on March 19, 2000 at 09:05:26:

I opened my mail today (I seem to do this everyday) and was delighted to find the Unicersity of Maryland Cooperative Extension Service newsletter had an article about fertilization. the sentence that delighted me stated, "Where turf or ground cover exist, subsurface fertilization should be the preferred method of fertilization."
verytreelylew

Reply to post by Ed Milhous, on March 11, 2000 at 09:37:10:

"The Research" that I've seen on this topic is rather limited in scope. It considers only a few basic growth responses to fertilization, rather than actual nutrient uptake and distribution.

Nitrogen is highly mobile, and volatile. It moves readily in the soil water, so can penetrate to deeper levels. Potassium can also move in the soil, depending on texture and CEC. Phosphorous does not readily move in the soil, binds readily to particles (does not leach), but does not extend to lower soil levels. Calcium also does not move rapidly. Other elements may distribute in the soil depending on their form and other soil conditions.

We know the trees have many feeder roots near the surface, and these may suffice to absorb much of the needed nutrients applied to the surface. However, we also know that roots grow where conditioins of oxygen, moisture and nutrients (and the lack of inhibiting contaminants) are suitable. The roots respond to favorable conditions (read high nutrient levels) by proliferating to take advantage of good supplies. Just ask Mr. Plumber.

If you dig up old augered fertilizer holes, you will often find them packed with roots the whole depth.

The point here is that the nutrients applied to the surface provide some basic benefits, and the tree responds. But allowing for volatilzation and runoff, higher amounts of some elements must be applied to achieve the same effect (A&L Agricultural Labs Technical Handbook). All of this is highly dependent on soil characteristics. Then add in the factor of competing turfgrass.

If the sole intent is to make your trees grow faster for awhile, broadcasting nitrogen is fine. I think it's too much of a generalization to say broadcasting is sufficient for trees, though.

Reply to post by JPS, on March 11, 2000 at 09:37:10:

Bingo!!! That was what I was waiting for, soil injection of fertilizers. What is nice about this is the soil is also fractured by the high pressure of water, injected with liquid fertilizer, and one can inject micchorizae. It is quicker and the fertilizer is better dispersed. I used this in very heavy clay soils with good results. The high pressure fractures the soil so the tool will penetrate better. Injection spacings is dependent upon tree size. This is a much better way to go. The word of caution here is timing. Do not fertilize too late in the year. The word in our area is not to fertilize after Flag Day. Late fall applications is permissible. I can recommend a good dealer if interested.

Reply to post by Russ Carlson, on March 19, 2000 at 09:05:26:

Fact is, we do not know whether ANY fertilization is benficial for trees. What is the right amount? I think the ANSI guidelines, which call for as much as 6 lbs. N per 1,000 sqft per year, can be excessive. What if I fertilize my lawn, too? Now I have put down 12 lbs. N per 1,000 sqft in one year, and I have followed published standards. I find situations where owners are doing this, and neither the lawn contractor nor the tree care contractor will admit to having done anything wrong! Is faster growth beneficial, especially for a tree that is probably in too small a space to begin with? As the late John Weidhaas said, are we treating the tree, or the customer? What if we fertilize for some period, and then stop? And where are the roots? In today's neighborhoods, if you want to fertilize your tree, perhaps you should fertilize the neighbor's yard!
I have done vertical mulching, other sub-surface fertilization, and surface broadcasting for 25 years; I can't tell any difference. What you use and when you use it is probably more important. Personally, I like natural organics; I would like to see them applied every year or every other year. I believe they improve the soil, which no other fertilizer will do, and help replace what is regularly removed from our fastidiously-kept yards.
As for tree and grass roots, agronomists I have talked with tell me that any soil (where grass is growing) favorable for tree root growth will also have grass roots in it. Can we get under grass roots via "deep-root fertilization"? I doubt it… seems to me that these two plants share the same soil. Any lawn I have ever dug in had both plants' roots in the same space.
I also have been told by agronomists that the soil organisms and plants move both calcium and phosphorus deeper into the soil more quickly than was thought in the past. Grass absorbs P and moves it internally into roots; when they die (which miles of them do every year), that P is released in a different place. Earthworms move P, both through their bodies and through the channels they dig.
Now, if your soil is so poor that you have no life in it… well that's another story. But in that case, your trees are probably hurtin' anyway.

Reply to post by Ed Milhous, on March 21, 2000 at 23:00:24:

Somewhere back among the threads here somebody posted about some research that suggested that the microflora communities found around tree roots and grass roots are vastly different.... trees' largely fungal while grass's largely bacterial. Don't recall if they were exclusive areas or mixed with the presence of grass tilting the balance around tree roots otherwise accustomed to fungi.

Point is there is at least that other variable that may affect use of fertilizers by the plants.

Reply to post by Ed Milhous, on March 21, 2000 at 23:00:24:

. . . .or treating the bank account. We'll assume that thte good readers here have other motives than just profit. [g]

The only point I differ on (from your previous screed) is the presence of soil organisms. The same customers who insist on the fertilization for both trees and lawn, probably rely heavily on various other lawn treatments as well- insecticides, herbicides, fungicides. So we end up sith a nearly sterile mineral soil condition. The nutrients are less likely to move in these conditions, but then, the tree probably can't utilize them anyway. Your suggestion of using organics is the best route.

Regarding the soil organisms- a personal anecdote: I have a river birch that is near the edge of mulched bed. Last fall I dug a small pit 8 feet from the base, and took about two quarts of soil. I did the same at 8 feet in the lawn area (I do not use any lawn treatments, even fertilizer). I sifted both samples and counted earthworms. 13 in the mulched area, 4 in the turf (actually 3 1/2). Although I did not analyze the roots, there were many more in the mulched sample. Soil was much more moist, too. The mulch had been in place only one year. The point is, if the worms don't like the soil, the tree roots probably don't either.

Reply to post by Scott Cullen, on March 27, 2000 at 09:16:16:

Grass may well exude chemicals that are fungistatic. They do limit growth of other plants; our good friends in turfgrass research are trying to improve upon this ability (turfgrass that controls weeds via chemicals), which could be a big problem for trees!
The larger numbers of fungi vis-a-vis bacteria may be due to soil content, too. I.e., I would expect to find more organic matter of a woody nature in tree root environments than in turf environments.

Reply to post by Russ Carlson, on March 27, 2000 at 09:16:16:

At least some customers do this (use chemicals to an extreme). It's not necessary, but we have allowed the lawn industry to get the upper hand with the public. They have good marketing and have gotten people's ear on landscape care. Note how many claim to provide tree and shrub care, too, when all they do is spray and fertilize. (I suppose we should be thankful, for the trees' sake, that they haven't gotten into pruning yet!)
Tree people need to learn more about lawns so that they can communicate intelligently with their customers, instead of simply stating that old line about getting rid of the grass. Fact is, too many suburbanites, if faced with having to choose between lawn and tree, would opt for the lawn!
By the way, my lawn is loaded with earthworms, not to the extent that the muched beds are, but they are out there doing their thing.

Reply to post by Ed, on March 27, 2000 at 15:35:02:

hi there,
on a web site dealing with "the soil food web" they analyse compostingof various ingredients and have come to the conclusion that the best compost for trees should indeed have a higher fungal than bacterial content.
this is achieved by ensuring that the materials to be composted have a higher carbon content than nitrogen. this would tie in to the idea that natural litter in a forest situation would have much higher bark and leave content hence carbon content and therefore would encourage or support a higher fungal content in the soil.
mark

Reply to post by Ed, on March 27, 2000 at 18:53:27:

My question created a very good discussion on the merts
of tree fertilization. However, my question is still
unanswered. I would like to know what type auger (s)
arborists are using for tree fertilization. I hate to make the
investment into a power auger unless experienced
arborists tell me so. Thanks.

Reply to post by Olen J Sharron, on March 28, 2000 at 09:41:46:

It's been many moons since I used (or caused to be used) a soil auger. When still on the commercial side, I had access to liquid injection equipment, so mostly used that.

Base your purchase decisions, like any other equipment, on the job you have to do. How often do you think you will need to use it? What type of soil do you deal with?

The augers come in many sizes and styles. Avoid the basic "flute welded to a shaft" type, as they will not last long. A twisted or forged spiral flute auger is more durable. Remember you only need go 6 to 10 inches deep, probably less in many cases.

The drilling device also depends on volume of use. The small gas-powered drills are nice for occassionial use, but will wear quickly if you have heavy clay or rocky soil, or hit a lot of roots. Electric works OK, but you need a power source. Either of these can really bang you up if they have high torque and then hit a root or rock.

The post-hole machines, with a pull-along engine and a shaft to the auger are great if you do a lot of this work, but are a bit pricey and more awkward to use on small jobs. They will last a long time, though. They won't twist on you and beat you with their handles, as the hand-held units might.

Reply to post by Olen J Sharron, on March 28, 2000 at 09:41:46:

Heard that a fellow at U MD broke an arm when the auger bit into compacted soil, not even a rock or root!
Olen, that soil in your area is going to be pretty tight, except in the bottoms.

Reply to post by Gerald, on March 17, 2000 at 21:27:54:

The fracture lines in the soil do not last long, unless they are filled with a non-compressable material. The weight of the soil causes them to collapse in short order. Injecting some material to keep that from happening was the idea behind the Terra-lift machine.

Reply to post by Ed, on March 29, 2000 at 15:25:28:

Thanks Ed and Russ for your input. Ed, I agree
with your comment about our soils. As Russ
suggested, not knowing how busy I will be
with fertilization, I will give an inexpensive
spiral fluted auger a try. Being self powered,
at least I won't break an arm. Thanks again.