Soil pH in Iowa, WI: Lime or Sulfur?

Typical topsoil pH in Iowa, WI

Typical topsoil in Iowa, WI is pH 6.39, already right for vegetable garden (6-7). Test before adding anything.

What Iowa needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.
• Sulfur: potatoes 2.1 lb/100 sq ft over 2 applications; blueberries 3.2 lb/100 sq ft over 2 applications; azaleas and rhododendrons 2.5 lb/100 sq ft over 2 applications; blue hydrangeas 2.5 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 6.39, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.

How mixed the soil is

Of the 480,727 surveyed acres in Iowa, WI, 53% are near neutral (6.5-7.3), 47% are moderately acidic (5.5-6.5). Mapped soils run from pH 4.3 to 7.7, a spread of 3.4 units across 643 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 17.6% clay and 2.79% 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. 2% of mapped components carry free carbonate (lime already in the ground).

Iowa against the rest of Wisconsin

pH 6.39 is 0.31 above the Wisconsin median of 6.08. 45 of 72 Wisconsin counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Sauk (6.17), Vernon (6.19), Pierce (6.2), Grant (6.39), Marquette (6.42), Kenosha (6.47), Racine (6.49), Lafayette (6.5).

The range in Wisconsin runs from Iron at 5.16 to Washington at 6.88; Iowa sits 72% of the way up.