Soil pH in Plymouth, IA: Lime or Sulfur?

Typical topsoil pH in Plymouth, IA

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

What Plymouth needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.
• Sulfur: potatoes 3.1 lb/100 sq ft over 2 applications; blueberries 4.8 lb/100 sq ft over 3 applications; azaleas and rhododendrons 3.7 lb/100 sq ft over 2 applications; blue hydrangeas 3.7 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 548,632 surveyed acres in Plymouth, IA, 64% are moderately acidic (5.5-6.5), 23% are alkaline (above 7.3), 13% are near neutral (6.5-7.3). Mapped soils run from pH 5.7 to 7.9, a spread of 2.2 units across 131 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 28.2% clay and 3.25% organic matter, which this site treats as clay. Moving it one pH unit takes about 11.5 lb of lime or 3.4 lb of sulfur per 100 sq ft. 23% of mapped components carry free carbonate (lime already in the ground).

Plymouth against the rest of Iowa

pH 6.39 is right at the Iowa median of 6.36. 55 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: Butler (6.38), Howard (6.38), Sac (6.38), Marshall (6.39), Ringgold (6.39), Winneshiek (6.39), Chickasaw (6.4), Dubuque (6.4).

The range in Iowa runs from Van Buren at 6.02 to Monona at 7.11; Plymouth sits 34% of the way up.