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Ph and sulfur
<Scott Briggs>
I recently performed a soil test at a clients home and was somewhat surprised by the results.

I did the test around a River Birch tree because I suspected a high ph. River Birch thrive in a soil ph of 6.5 and are naturally resistant to many types of leaf scortch and blight type diseases when conditions are ideal.

This tree is suffering from a severe case of some type of leaf scortch and/or leaf blight.

The ph came back as 7.7. Levels for all micro nutrients are high with the exception of calcium, which is very high. Levels for macro nutrients are moderate with the exception of nitrogen, which is very low. Salinity and sodium levels are none and low, perspectively.

The thing that through me for a loop, is that the level of sulfur is high, 58 ppm. If sulfur is used to decrease ph, how can you have an alkaline soil with high levels of sulfur?

The lab that did the test made recommendations for correcting the nitrogen level but did not make any suggestions on reducing the ph.

Should I add more sulfur to the soil? Is there another way to reduce ph besides the use of sulfur?

Any and all suggestions will be appreciated, thanks.
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<James Causton>
Reply to post by Scott Briggs, on October 11, 2001 at 13:06:00:

Hi Scott, What else has happened on the site??? Is there a chance that some cement/ concrete was recently poured? is there a chance that "someone" tried to correct the ph using sulphur? Where could the sulphur have come from???? I am not sure it would be a good idea to simply reduce the ph. without understanding why it is so high,

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<Russ Carlson>
Reply to post by Scott Briggs, on October 11, 2001 at 13:06:00:

I think you answered your own question, Scott. you have a soil with high pH because of the calcium. Although the sulfur levels are high, the very high calcium counters it.

This sounds like a lawn area that is highly fertilized and limed. When the pH goes up, some nutrients are tied up in the soil and unavailable to the plants, even if they are in relatively high amounts.

Forget the nitrogen for now. Fix the pH first, then retest and deal with other issues later. Nitrogen drops a bit at higher pH levels, and with the seasons.

Add elemental sulfur. Depending on the soil texture, the amount will vary. Clay soils need much more than sandy soils to change the pH the same amount. Start by adding about 6 pounds sulfur per 1000 square feet of surface area, then wait 2 or 3 months and retest the soil pH. Make another application of 6 pounds/1000 sq ft, wait and retest. Don't try to change too much at once or "root burn" may occur. Be sure to wait a few months before testing and reapplying.

[Note: these are general recommendations only. Without access to the full information and soil analysis, specific recommendations cannot be made accurately.]
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<Bob Underwood>
Reply to post by Russ Carlson, on October 11, 2001 at 13:06:00:

This past week at the SMA convention in Fargo, I saw a soil test that had been performed on some soil from East of the Urals in Russia. It had a pH of 7.6 and the sulfur reading was clear off the chart in the bar graph on the report. I don't remember the amount, but several comment on how high the S was at the same time the pH was slightly high. Most of us in the Dakotas would have killed for soil as good as that test.
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<Dave G Meadows>
Reply to post by Scott Briggs, on October 11, 2001 at 13:06:00:


I remember an issue of the Arborist News (Dec/2000) which featured an article written by Bruce Hagen, titled: Back to Basics: Tree Fertilization. This was perhaps the best information I have seen so far on the subject of soil chemistry, and in particular, soil reaction or pH.

I suggest ordering this back issue if you need to understand the dynamics involved, but here is a bit of a summary, FYI:

Your soil test confirms low salinity, therefore it is likely that the alkaline soil is sodic or high in sodium (Na). Your test should identify the level of Na.

Elemental sulfur (S) is usually applied when a soil is high in salinity, as the sulfur reacts in the presence of water and oxygen to form sulfuric acid (H2SO4) which in turn reacts with lime (CaCO3) to yield gypsum (CaSO4).

To accomplish the same result in a sodic (not saline) soil, the high concentration of sodium (Na) is blocking the process. Therefore, thoroughly mixed gypsum (CaSO4) must be added directly to the soil to replace the sodium (Na) with Calcium (Ca). This reaction forms sodium sulfate (NaSO4) which is readily soluble, allowing the sodium (Na) to leach away when irrigated. This is the key to lowering the pH in a sodic soil.

Alkaline soils are also poorly aggregated (no large particles to increase pore spaces), lack oxygen, are poorly drained, yet difficult to wet. Therefore, regularly top dressing or mulching the entire yard area as well as the tree's drip line using well rotted compost is probably the best maintenance solution for long term stability and tree health.

This is why I firmly believe that qualified Arborists are needed to address the complex issues of tree care in today's environment. Research builds our knowledge and knowledge improves our decision making.

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