Soil pH in Wapello, IA: Lime or Sulfur?

Typical topsoil pH in Wapello, IA

Typical topsoil in Wapello, IA is pH 6.21, already right for vegetable garden (6-7). Test before adding anything.

What Wapello needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.
• Just outside, test first: potatoes (off by 0.2), azaleas and rhododendrons (off by 0.2).
• Sulfur: blueberries 2.8 lb/100 sq ft over 2 applications; blue hydrangeas 2.3 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 6.21, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, potatoes, strawberries, roses, azaleas and rhododendrons, pink hydrangeas.

How mixed the soil is

Of the 272,338 surveyed acres in Wapello, IA, 64% are moderately acidic (5.5-6.5), 36% are near neutral (6.5-7.3). Mapped soils run from pH 5.5 to 7.4, a spread of 1.9 units across 418 soil components. 64% 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 25.7% clay and 2.88% 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. 0% of mapped components carry free carbonate (lime already in the ground).

Wapello against the rest of Iowa

pH 6.21 is 0.15 below the Iowa median of 6.36. 14 of 99 Iowa counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Henry (6.18), Page (6.18), Sioux (6.2), Marion (6.21), Appanoose (6.22), Davis (6.22), Adair (6.25), Adams (6.25).

The range in Iowa runs from Van Buren at 6.02 to Monona at 7.11; Wapello sits 17% of the way up.