Soil pH in Monroe, IA: Lime or Sulfur?

Typical topsoil pH in Monroe, IA

Typical topsoil in Monroe, IA is pH 6.15, already right for vegetable garden (6-7). Test before adding anything.

What Monroe needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, strawberries, roses, pink hydrangeas.
• Just outside, test first: tomatoes (off by 0), 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 2.1 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 6.15, 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 273,962 surveyed acres in Monroe, IA, 70% are moderately acidic (5.5-6.5), 30% are near neutral (6.5-7.3), 1% are alkaline (above 7.3). Mapped soils run from pH 5.4 to 8, a spread of 2.6 units across 278 soil components. 70% 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 26.2% clay and 2.93% 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. 1% of mapped components carry free carbonate (lime already in the ground).

Monroe against the rest of Iowa

pH 6.15 is 0.21 below the Iowa median of 6.36. 7 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: Shelby (6.11), Lee (6.12), Montgomery (6.12), Cass (6.13), Jefferson (6.16), Crawford (6.17), Cherokee (6.18), Henry (6.18).

The range in Iowa runs from Van Buren at 6.02 to Monona at 7.11; Monroe sits 12% of the way up.