SOIL pH - Alkalinity and Acidity of the soil

Soil pH is referred to as the "acidity" of the soil and is measured by the number of Hydrogen ions present in the soil solution.  Since S.W. Pennsylvania receives considerable rainfall every year, and since rain is H2O, soils tend to revert back to an "acid condition." Ammonium fertilizers also have an acidifying effect on the soil.

Soil Acidity and Alkalinity

When the soil pH is too "acid" (low pH) or "alkaline" (high pH), nutrients present in the soil become locked-up or unavailable.  Correcting the pH has the same effect as applying fertilizer since it "unlocks" plant nutrients already present.
   

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 Note: this a Logarithmic Scale 
 based on the "powers of ten" 

* pH 6.0 is  10-times 
more acidic than pH 7.0

* pH 5.0 is  100-times 
more acidic than pH 7.0

SUMMARY
   
Most plants grow best within a pH range of 6.5 to 7.2 (7 is neutral) The best way to find out what your soil needs is by sending a sample to a soil lab.  Penn State Cooperative Extension agents sell soil test kits with instructions for your own use, or Donnan Landscape Services can handle the soil testing for you. 
   
The soils we've tested in the South Hills of Pittsburgh, and Washington County, over the past 20 years, tend to need both lime and phosphorus.  The primary exception would be soils located in "bottom ground" (near a stream or river) which usually don't require lime.  Of those soils requiring lime, dolomitic lime (high in magnesium) usually fits the test recommendations the best.
   

 More soil pages

• Soil amendments
• Fertilizer
• Lime and liming
• Soil
• Soil tests