Soil pH in Northampton, PA: Lime or Sulfur?

Typical topsoil pH in Northampton, PA

Typical topsoil in Northampton, PA is pH 5.68, too acidic for vegetable garden. Expect roughly 5.6 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Northampton needs, by plant

• Already in range: potatoes, strawberries, azaleas and rhododendrons.
• Just outside, test first: blueberries (off by 0.2), blue hydrangeas (off by 0.2).
• Lime: lawn (cool-season grass) 5.6 lb/100 sq ft over 2 applications; vegetable garden 5.6 lb/100 sq ft over 2 applications; tomatoes 5.6 lb/100 sq ft over 2 applications; roses 5.6 lb/100 sq ft over 2 applications; pink hydrangeas 4.2 lb/100 sq ft.

What to do next

If your test confirms pH near 5.68, spread about 56 lb of ground limestone per 1,000 sq ft of vegetable bed in 2 doses, ideally in fall.

How mixed the soil is

Of the 200,169 surveyed acres in Northampton, PA, 49% are strongly acidic (below 5.5), 34% are moderately acidic (5.5-6.5), 18% are near neutral (6.5-7.3). Mapped soils run from pH 4.2 to 6.7, a spread of 2.5 units across 422 soil components. No single class covers 60% of the county, so two gardens a few miles apart here can need opposite treatments. Test your own bed.

Clay, organic matter and rates

Topsoil here averages 18.9% clay and 2.97% organic matter, which this site treats as loam. Moving it one pH unit takes about 7 lb of lime or 2.3 lb of sulfur per 100 sq ft. None of the mapped components carry free carbonate.

Northampton against the rest of Pennsylvania

pH 5.68 is 0.37 above the Pennsylvania median of 5.31. 52 of 67 Pennsylvania counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Allegheny (5.6), Lebanon (5.63), Tioga (5.65), Bradford (5.68), Berks (5.69), Susquehanna (5.72), Mercer (5.74), Lehigh (5.77).

The range in Pennsylvania runs from Forest at 4.57 to Greene at 6.07; Northampton sits 74% of the way up.