Soil pH in Rock Island, IL: Lime or Sulfur?

Typical topsoil pH in Rock Island, IL

Typical topsoil in Rock Island, IL is pH 6.51, already right for vegetable garden (6-7). Test before adding anything.

What Rock Island needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, roses.
• Just outside, test first: strawberries (off by 0), pink hydrangeas (off by 0).
• Sulfur: potatoes 2.3 lb/100 sq ft over 2 applications; blueberries 3.5 lb/100 sq ft over 2 applications; azaleas and rhododendrons 3 lb/100 sq ft over 2 applications; blue hydrangeas 3 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 6.51, 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 255,558 surveyed acres in Rock Island, IL, 64% are near neutral (6.5-7.3), 33% are moderately acidic (5.5-6.5), 3% are alkaline (above 7.3). Mapped soils run from pH 5.7 to 7.9, a spread of 2.2 units across 317 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 21.8% clay and 2.38% 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. 4% of mapped components carry free carbonate (lime already in the ground).

Rock Island against the rest of Illinois

pH 6.51 is 0.11 above the Illinois median of 6.4. 75 of 102 Illinois counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Douglas (6.48), Marshall (6.5), La Salle (6.51), Menard (6.51), Boone (6.52), Scott (6.52), DeKalb (6.53), Edgar (6.53).

The range in Illinois runs from Pope at 5.5 to Grundy at 6.75; Rock Island sits 81% of the way up.