Re: [SG] Hydrangeas (lowering pH)

In a message dated 6/17/99 6:15:32 AM Central Daylight Time, eoneill@IBM.NET
writes:

<< Do I need to get out the aluminum sulfate?

 Gerry >>

Hi Gerry and all,

Your question prompts me to ask why people seem to prefer using aluminum
sulfate rather than iron sulfate.  I have a 1996 handout from the Univ. of MN
called "How to Lower Soil pH" which credits Carl Rosen, Extension Soil
Scientist at the U of MN for the information.  It talks about elemental
sulfur, aluminum sulphate and iron sulphate.  I'll just quote the 1st
paragraph:

"The table on the back side of this sheet shows the number of pounds of
elemental sulfur or iron sulfate required per 100 square ft. to lower the
soil pH from its existing level to 6.5.  Elemental sulfur is available under
various product names, one of which is Dispersol.  However, it takes 3-4
months with elemental sulfur for the pH change to occur once added to the
soil.  Iron sulphate and aluminum sulphate will also lower the pH, but they
are 6 to 7 times less effective than elemental sulfur on a weight basis.
HOWEVER, ALUMINUM SULPHATE IS NOT RECOMMENDED FOR LOWERING SOIL PH AS IT HAS
BEEN FOUND TO HAVE POTENTIALLY TOXIC EFFECTS SUCH AS RESTRICTING ROOT GROWTH
AT LOWER PH LEVELS.  If you want to lower the soil pH faster than with
elemental sulfur, iron sulphate would be the recommended choice as the
reaction time for the pH change is usually 2-3 weeks."

It further says you can help MAINTAIN the lower pH by applying nitrogen
fertilizers that contain ammonium.  "Ammonim sulfate is the best acidifying
nitrogetn fertilizer source and should be applied at label recommended rates."

It also warns about using personal protection when applying it as it's a fine
dust and to wear coveralls to avoid rusty stains all over your clothing.
Wash them separately from the non-gardening clothing after presoaking them in
cold water to remove most of the dust.

Any thoughts? Is aluminum sulfate easier to come by? or cheaper?  I did just
buy some of the aluminum sulfate after reading how it gets rid of slugs,
rather than to reduce my pH.

Thanks,
Cindy Johnson
White Bear Lake, MN
zone 4a
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index