Donn, although you indicate you are no longer participating in this thread, I am more than happy to address your statements. I opted not to because you are correct in stating this is often the course these internet dialogs follow - I offer scientifically based information, you refute with anecdotal experience that seems to contradict the science and the entire discussion deteriorates into an argument that is pointless and just causes ill-will and bad feelings. You stated that amending an entire planting area is often impractical and "flies in the face of reality". Ideally, the planting area should be amended, if necessary, before any planting takes place. If that is not possible and amending is still deemed necessary, then layering the amendments as a mulch on the top of the existing soil is preferred over incorporating them into a small planting hole. The ultimate effect will be the same - it just takes a bit longer to achieve. In many cases, if the soil is decent and well draining, no amending is necessary for trees, shrubs and perennials other than to replace organic matter periodically which is most easily accomplished by mulching or topdressing. As to "flying in the face of reality", I believe you are misunderstanding what 'amending' refers to - placing a containerized plant grown in a conventional potting medium into a planting hole is not amending - that is simply planting. Incorporating or adding soil additives to the indigenous soil or backfill is amending. Loosening or otherwise disturbing the indigenous soil before planting but not including any additives is modifying the soil, a highly desireable planting activity that is frequently overlooked or given short shrift. But you make a valid point about being concerned with the container soil being a different structure and composition from the indigenous or existing soil. And yes, an interface situation is created under these conditions. You might be surprised to know that there are a good many professionals that recommend bare rooting all containerized or B&B plants prior to planting to eliminate this issue, such as Pablo indicates he does. At the very least, any loose or excess potting medium should be shaken off and the roots teased and straightened. And I would definitely recommend bare rooting B&B material, as these are typically grown in heavy clay soils for ease of harvesting and the interface issue is especially strong in these situations but tends to work in reverse - should the clay rootball dry out, which is quite common since soil moisture is unable to move through clay at the same rate it would move through a more loamy soil, it is very difficult to rehydrate and the plant will suffer from drought stress. So let's look at soil interface. This occurs any time two different soil structures are juxtaposed. It affects permeability - water is unable to percolate through the different soils smoothly and unobstructed - which in turn can affect drainage. It also hinders root development, typically creating what is often referred to as "lazy root syndrome", wherein roots are not encouraged to move out into the unamended soils and remain circling around in the amended portion only. This results in poor performance and often stunted or less than optimal growth. Roots are far and away the most significant portion of the plant and a healthy, well-developed root system is paramount in the success of any planting. It would appear to be obvious that whatever one can do to encourage a wide-spreading root system and its ability to access necessary nutrients and soil moisture should be preferrable than to help to limit the root spread by a too small or too rich planting hole. This is where the $50 planting hole for the $5 plant comes into play - the Cadillac of planting holes is NOT dependent on adding amendments. It IS dependent on thoroughly preparing the planting hole by modifying or loosening the soil over a wide area so that roots are able to spread freely and providing a planting hole that is suffciently wide enough to allow the roots from the container to be spread out fully yet not too deep or with a highly loosened base so that settling occurs. Wide and shallow is preferred - 3-5 times the width of the current rootball and slightly less than the depth of the rootball. In fact, planting high is almost always a preferred practice. As to why the interface issue is of less concern when amending an entire planting area as opposed to individual planting holes is pretty much self-explanatory. The larger the area you amend, the more subtle the change in soil structure and the less abrupt the interface is. Amending a large area effectively changes the structure of the indigenous soil. Water is able to move through this widely amended area more smoothly and roots are able to travel freely without obstruction. As to the "bathtub" effect, it doesn't require heavy or clay soils to exist. Planting holes that have been well amended with organic matter tend to be much more moisture retentive than those that have not been (the interface issue again) so moisture will persist in this area immediate to the roots longer than if the hole was not amended, often too long. This creates problems with lack of oxygen and the potential for root rots. In heavy clay soils, this problem is exacerbated. The solution is to dig very wide but shallow planting holes and plant high, with the top of the root ball above the soil level and mulch with your preferred amendments to make a low mound. This is the mini equivalent of creating a berm or raised planting area and will encourage far better drainage and root development than a smaller and deeper planting hole. You indicate that you have a sandy loam. That is a highly desired soil type that few gardeners are fortunate enough to come by naturally. It's loose, friable and naturally well-draining. With the exception of adding organic matter periodically as a mulch or top dressing, no amending should be necessary. And growing tomatoes or other annual crops is not quite the same as planting landscape ornamentals or other long term/permanent plantings. Generally annuals and veggies are planted in a well-prepared and amended bed anyway and adding further amendments is unlikely to change the soil structure significantly or create substantial interface issues. And annual crops, by virtue of their being a single season plant, do not have the same requirements for long term growth and root development than does a tree or shrub, for example. I could list numerous citations to support these contentions, just as you can still find many sites that still recommend amending planting holes. News doesn't always travel very rapidly, even in these days of the Internet and instant messaging and frankly, many folks are unwilling to change or try something outside of their immediate comfort zone. That doesn't change the science behind it nor the validity of the information. And as I stated before, if what you do currently works for you and you are happy with the results, then I see little reason for you to change. However, not everyone gardens in the same circumstances and what works for you may very well not work for someone else. Perhaps this additional information will provide others with better options and more successful gardens.

When discussing soil organic matter fractions or percentages it is critical to distinguish what is being reported or discussed. Is it volume percent or weight percent that is being discussed? Soil labs and soil scientists commonly report and discuss soil fractions on a dry weight basis. That would include the familiar recommendations for soil OM in the range of 5-10%, as well as lab reported test results of organic matter. That is a weight fraction, based upon oven dried weights. The bulk density of soils and organic materials is commonly reported on a dry weight basis. A fairly typical, average mineral soil bulk density is ~ 2600 lbs/cubic yard. The typical bulk density, again dry weight basis, for common soil organic amendments (e.g. compost) is ~ 1,000 lbs per cubic yard. The typical OM bulk density is only ~40% of that of a baseline mineral soil, and the range can be about 25% to 50%. As an example, consider the johnhughes 25% compost number as a volume fraction - mix 1 yard of compost (dry bulk density 1,000 lbs/yard) with 3 yards of mineral soil (dry bulk density 2600 lbs/yard) to produce 4 yards of soil, total weight 8800lbs. Assume everything is at a comparable moisture level. While the mix fraction was 25% by volume, the weight fraction will be ~ 11%, and that is what a soil lab test of OM would ideally report. As a general rule-of-thumb for soil mixtures, the net weight fraction (percent) of organic matter will be ~ 1/2 of the volume fraction, again assuming similar moisture levels for the mineral and organic phases. Hence the familiar 5-10% soil OM recommendation translates to 10-20 % soil OM by volume. So if you wanted to increase soil OM by 7.5% (weight) you would add 15% OM by volume, or nearly 1-inch of OM on top then mixed into 6 inches of underlying soil. That's not allowing for the issues associated with testing for OM. This post was edited by TXEB on Fri, Sep 6, 13 at 0:32

How do I know about all this? It's my job :-) In additional to being a landscape designer, I am a consulting horticulturist and a horticultural educator. I am sure you are just as proficient and knowledgeable about your profession. There will always be a lot of varying opinions on how to do things, depending on one's personal experience and how current they are with up-to-date horticultural practices. Sometimes the older, highly work-experienced folks (like maybe your arborist?) are years removed from the classroom or even any professional or technical publications so they are not aware of the newest technology and current, revised methods. Trees competing with grass (or vice versa) can be an issue but only when dealing with young, newly planted and unestablished trees. If your magnolia has been in place for 3 years or more, then this is no longer a concern - the tree is established. And your yardman doesn't have it quite right - grass needs nutrients just like the tree does. It doesn't give them up to the tree. That's why there can be issues with young trees planted in the middle of a lawn - both fight for the same nutrients and moisture. But when you fertilize a lawn that has a tree growing in it, the tree benefits from the fertilizer just as the grass does. Leaving an area surrounding an established tree free of lawn is more a matter of maintenance than it is necessarily for the health of the tree. It is just a whole lot easier to mow and edge when you do not have to deal with a tree trunk in the way! With small, young trees it is even more important to leave a clear area as they CAN be easily damaged (and even killed) by mowers and string trimmers. And you never want to leave clear areas unmulched. Mulch keeps the weeds down and insulates the soil, reducing evaporation and therefore the need for additional watering. Asking for additional opinions is never a bad thing so no worries about posting your question on the Trees forum. The guys over there and I agree in general about most things tree-wise :-) And you'll find me responding in a bunch of different forums. My interests are very broad, as is my experience, and the teacher in me just has to come out when someone asks a question that I feel they will benefit from my answering.

I'm in E. Tn. When you had your soils sent out, did they do pH and organic matter tests? The last time I checked (which was just last year,) they had made changes in the way they tier the testing. It was like $15 for a basic test, and another $15 for an advanced test (which required another sample box.) I didn't call the agent back, but it wasn't exactly clear in the paperwork about what you get (outside of nutrition analysis) with the first test. One paper said that you get pH also, and another paper said that pH and organic matter were in the second test. I decided not to get the test, so I didn't call to have that straightened out. However, in your case, that's the route to go. Call your agent. Don't worry about getting them out there, just ask about the testing, and have them send you the boxes. You're going to want pH and organic matter. But... really, if your land had been grazed in the past like many of the areas around here, they were badly over-grazed. And that mining you mentioned surely didn't help matters. The test has a form to fill out, and you can let them know what usage you have planned for the acreage - you've probably already done that. All that said, if it's anything like this area, you basically need organic matter, and a lot of it. Don't worry so much about those who give you percentage of OM for soils... here in Tn. we are hot and wet. Organic matter decomposes extremely quickly here. You can't even just leave it on the surface and wait for the soil life to incorporate it, you need to get it under ground, into at least the top 8". The way you do that is to turn everything you can under, and then do as glib suggests, choose appropriate cover crops. Don't worry, there's little chance of exceeding OM percentage. It will come down to just practicality of how much you can work in long before you have too much organic matter. After the soil has recovered some, then you can start managing OM levels. At least that's what I would suggest.