Soil pH in Knox, IN: Lime or Sulfur?

Typical topsoil pH in Knox, IN

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

What Knox 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 325,281 surveyed acres in Knox, IN, 71% are moderately acidic (5.5-6.5), 28% are near neutral (6.5-7.3), 2% are strongly acidic (below 5.5). Mapped soils run from pH 5 to 8.1, a spread of 3.1 units across 98 soil components. 71% 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 19.5% clay and 2.2% 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).

Knox against the rest of Indiana

pH 6.21 is 0.14 below the Indiana median of 6.35. 28 of 92 Indiana counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Daviess (6.18), Vanderburgh (6.19), Franklin (6.2), Bartholomew (6.21), Sullivan (6.21), Dearborn (6.22), Posey (6.22), La Porte (6.23).

The range in Indiana runs from Brown at 4.97 to Hamilton at 6.74; Knox sits 70% of the way up.