I have been using Medicap Fe trunk implants very successfully to fight iron chlorosis in my many pin oak trees for 15 years. Soil samples show my pH to be 7.3 minimum and 7.6 near our long concrete cement driveway. The soil report recommendation is to add 32 pounds of sulphur (sulfur) to a depth of 12 inches per 1000 square feet (or 8 pounds to a 3 inch depth). Several internet sources recommend putting the sulphur in approx. 12 inch deep holes in a 2 foot by 2 foot grid around the tree. They also suggest a 1 to 1 ratio of sulphur and iron sulfate (ferrous sulphate/copperas) to add iron in addition to lowering the pH. Question 1: Will the localized high sulphur concentrations do harm to the trees? Question 2: What is the highest sulphur application rate for grass (lawn) (bluegrass and fescue) without damaging it?
To acidify your soil, the sulfur must be converted into sulfuric acid by soil bacteria. This happens slowly. For best results, make several light applications repeatedly instead of applying the entire amount all at once. This will help prevent killing the beneficial soil fungi since sulfur is a natural fungicide. It helps if there is a good leaf mulch that has started to decompose into leaf mold. (Oaks really need this in their root zone.) Then the sulfuric acid will be formed on the soil surface, and you won't have to dig. (Digging in the root zone of an oak can kill the tree.)
You should also add some gypsum (calcium sulfate). A significant amount can be added without the damage that might be caused by a significant amount of elemental sulfur.
In the end, you will find that it takes more work and time to acidify an alkaline soil than it takes to neutralize an acidic soil.
By the way, in my area, native oaks thrive in the native soil, which tends to be alkaline. However, pin oaks (Quercus palustris) are native to the eastern U.S. where many soils are indeed acidic, not California.
One of the problems with lowering the pH with sulfur is that the soil will revert back. Something that may interest you. I did a few soil studies on my own in old growth forest. We tested for many essential elements and pH. In a old growth forest which contained white pine and hemlock we got a pH average of
4.2 in the upper four inches of soil. This sample was taken from Pennsylvania with the approval of the US Forest Service. I took the samples in the area of soil where the mycorrhizae and rhizoplane was. Not inside the rhizoplane. I understand that it is very difficult to get samples actually from the rhizoplane. That is really where the samples should come from because you will get different results there. As far as turf goes, it likes high pH. Properly applying mulch could greatly help your situation. Correct Mulching "suggestion". See "proper mulching".
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well written articles on soil chemistry and such are here:
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[The soil report recommendation is to add 32 pounds of
The rhizoplane and rhizosphere where the absorption takes place, is usually in the upper four inches of soil. There is no way I would put the sulfur
12" deep. I would think it would move downward rather then upward. Actually I would
I have a well. From which the well pump draws water. In this water is much diluted hydrogen sulfide gas. To reduce this gas significantly, I use a aerator bottle. The bottle then carries a significant amount of diluted sulphuric acid. Every 24 hours by a timer, the bottle is flushed with the same water. Total flush amount is 35 gallons. The ingredients go to a french drain consisting of limestone rock of all different sizes. The drain area is 10' wide X 10' long X 8' deep. The french drain is uphill from several live oaks in the yard proper. During heavy rain periods, above the french drain, the St. Augustine is very spongy when walking on it. Has been this way for 2 years now.
Its obvious to me the live oaks immediately downhill from this french drain are getting various amounts of, and various concentrations of H2SO4 (sulfuric acid). Yet, appear no different than other live oaks growing wild in the surrounding area. The closest live oak has its trunk within 15 ft of the french drain boundary on the downhill side from the french drain.
Native surface soil is nil to insignificant. Surface soil is generally a gray clay that is always very quick to dry. Subsurface is fractured limestone and caliche.
Is this addition of diluted sulphuric acid detrimental or aiding to the soil and subsurface soil, or the live oaks themselves? Dave
I think you said it when you said "The ingredients go to a french drain consisting of LIMESTONE rock of all different sizes." The acid eats the limestone and neutralizes it. Hence no change in the pin oaks.
One thought is you could monitor the vitality of the trees with a Shigometer. One function of the meter is to measure the Cambium Electrical Resistance (CER). You could monitor the vitality of your live oaks with the meter. I have one and need to use it more in consulting. It is more accurate than just a casual observation. I could go into more detail and better explain the process if you like. I have records on the CER of live oaks at Tulane University in Louisiana. The test were taken from 11-16-1998 and 11-20-1998. The mean of 40 trees tested at breast height was 6.3. Out of the 40 trees the low number was 4.1 and the high number was 10.7.
At the base of the trees the flare, which is trunk tissue, was tested and suggested in some cases that there was woody root symplast decline. The mean trunk flare out of 11 trees tested was 5.7. I.e., Trunk flare CER mean of 5.7. The trunk flare high was 19.8 and the low was 3.1. When there is more electrical resistance of the trunk flare, compared to the reading at breast height, than I believe there is a suggestion that the woody root associated with that trunk flare, is in a state of decline. I read data suggestioning such observations and I cannot find the doc. I know I read it and filed the paper in my files but I just can't find it. The work and paper may have been by Dr. Shortle with the USFS. He did many studies with the Shigometer. Again, if anybody on the list is in PA, NJ or MD, I could demonstrate the meter.
> Two well written articles on soil chemistry and such are here:
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Thank you for your excellent comments and references. They are fascinating. It appears, however, your last thought got cut off. You said: "The rhizoplane and rhizosphere where the absorption takes place, is usually in the upper four inches of soil. There is no way I would put the sulfur
12" deep. I would think it would move downward rather then upward. Actually I would" (WOULD WHAT???)
Thanks for your insights. One question, however. You said: "For best results, make several light applications repeatedly instead of applying the entire amount all at once." Can you put a number on a "light" or "heavy" application? How would you rank 8 lb. sulphur per 1000 sq.ft.?
I am not sure. I would place it on top and then apply mulch over it? Just a thought. Also a biodynamic farmer once explained to me that any chemicals going to the tree, can be mixed in the chip pile as it is composting. He placed everything he was adding to the chip pile and then to the tree. Just a thought.
I would apply a third at annual intervals in the early spring. Yes, that means it takes three year to do it all.
In an alkaline soil, the acid might be neutralized almost as quickly as it is formed. Thus, you want a continuous seeping of acid over time, to finally overcome the alkalinity.
In any case, the conversion of sulfur into sulfuric acid is slow. You won't speed it up by applying extra sulfur, but you might have an adverse impact on beneficial soil organisms if you apply too much at one time.
Note that, if you have a good mulch of compost or composting leaves, you don't have to dig the sulfur into the soil. Just rinse it through the mulch, which already contains acidifying bacteria. Sulfur won't dissolve and leach into the soil, but sulfuric acid will indeed leach into the soil.
Once you get the results you want, you should probably broadcast a smaller amount of sulfur and gypsum together, each spring. If your soil is naturally alkaline (as mine is), the acid will eventually be neutralized no matter what you do. So you must keep renewing the acid.
I mix a double handful of sulfur and a double handful of gypsum and broadcast that around my liquidambar tree each spring to prevent cholorsis. (A landscaper suggested adding about 1/4 cup of Epsom salts, which is magnesium sulfate.) With the first feeding of my roses, I include about a handful of sulfur for each rose bush; I also include about a tablespoon of Epsom salts because the magnesium promotes the growth of new canes. I don't usually add sulfur elsewhere in my garden because I use a lot of ammonium sulfate as a fertilizer. My camellias and azaleas get an acidic commercial fertilizer specific for them. My citrus and gardenia get either the ammonium sulfate or commercial citrus food, which is acidic; they also get added zinc sulfate. Finally, I use a very large amount of gypsum (calcium sulfate), about 1 lb a year per
100 square feet; this I generally broadcast in the late fall, just before the winter rainy season.
You will notice that, although I don't use sulfur all over my garden, I do use sulfur-containing fertilizers. However, I avoid using these on iris, primroses, and dianthus, all of which prefer an alkaline soil. It gets tricky since I have dianthus right next to azaleas.
BTW I am not a big fan of injections and implants. Implants can kill alot of the parenchyma cells if I recall correctly. As a person that offers organic tree care as a profession, I tend to try to protect the symplast.
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