Soil pH in Penobscot, ME: Lime or Sulfur?

Typical topsoil pH in Penobscot, ME

Typical topsoil in Penobscot, ME is pH 4.97, too acidic for vegetable garden. Expect roughly 10.5 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Penobscot needs, by plant

• Already in range: blueberries, azaleas and rhododendrons.
• Just outside, test first: potatoes (off by 0), blue hydrangeas (off by 0).
• Lime: lawn (cool-season grass) 10.5 lb/100 sq ft over 3 applications; vegetable garden 10.5 lb/100 sq ft over 3 applications; tomatoes 10.5 lb/100 sq ft over 3 applications; strawberries 7 lb/100 sq ft over 2 applications; roses 10.5 lb/100 sq ft over 3 applications; pink hydrangeas 9.1 lb/100 sq ft over 2 applications.

What to do next

If your test confirms pH near 4.97, spread about 105 lb of ground limestone per 1,000 sq ft of vegetable bed in 3 doses, ideally in fall.

How mixed the soil is

Of the 2,016,715 surveyed acres in Penobscot, ME, 78% are strongly acidic (below 5.5), 16% are moderately acidic (5.5-6.5), 6% are near neutral (6.5-7.3). Mapped soils run from pH 3.9 to 7.1, a spread of 3.2 units across 1,252 soil components. 78% of the land falls in one class, so the county figure is a fair first guess for most yards here.

Clay, organic matter and rates

Topsoil here averages 12% clay and 3.65% 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.

Penobscot against the rest of Maine

pH 4.97 is 0.09 above the Maine median of 4.88. 14 of 16 Maine counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Sagadahoc (4.92), Lincoln (4.93), Washington (4.93), Androscoggin (4.94), Cumberland (5.01).

The range in Maine runs from Piscataquis at 4.59 to Cumberland at 5.01; Penobscot sits 90% of the way up.