Soil pH in Mobile, AL: Lime or Sulfur?

Typical topsoil pH in Mobile, AL

Typical topsoil in Mobile, AL is pH 5, too acidic for vegetable garden. Expect roughly 4.5 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Mobile needs, by plant

• Already in range: potatoes, blueberries, azaleas and rhododendrons, blue hydrangeas.
• Lime: lawn (cool-season grass) 4.5 lb/100 sq ft; vegetable garden 4.5 lb/100 sq ft; tomatoes 4.5 lb/100 sq ft; strawberries 3 lb/100 sq ft; roses 4.5 lb/100 sq ft; pink hydrangeas 3.9 lb/100 sq ft.

What to do next

If your test confirms pH near 5, spread about 45 lb of ground limestone per 1,000 sq ft of vegetable bed, ideally in fall.

How mixed the soil is

Of the 659,034 surveyed acres in Mobile, AL, 93% are strongly acidic (below 5.5), 5% are moderately acidic (5.5-6.5), 2% are alkaline (above 7.3). Mapped soils run from pH 4 to 7.9, a spread of 3.9 units across 248 soil components. 93% 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 9.6% clay and 2.23% organic matter, which this site treats as sandy. Moving it one pH unit takes about 3 lb of lime or 1.2 lb of sulfur per 100 sq ft. None of the mapped components carry free carbonate.

Mobile against the rest of Alabama

pH 5 is 0.15 below the Alabama median of 5.15. 8 of 67 Alabama counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Fayette (4.94), Baldwin (4.96), Etowah (4.97), Marion (4.98), Cherokee (5.02), Choctaw (5.02), St. Clair (5.02), Chilton (5.03).

The range in Alabama runs from Randolph at 4.89 to Lowndes at 6.25; Mobile sits 8% of the way up.