Soil pH in Knox, KY: Lime or Sulfur?

Typical topsoil pH in Knox, KY

Typical topsoil in Knox, KY is pH 5.66, too acidic for vegetable garden. Expect roughly 5.6 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Knox needs, by plant

• Already in range: potatoes, strawberries, azaleas and rhododendrons.
• Just outside, test first: blueberries (off by 0.2), blue hydrangeas (off by 0.2).
• Lime: lawn (cool-season grass) 5.6 lb/100 sq ft over 2 applications; vegetable garden 5.6 lb/100 sq ft over 2 applications; tomatoes 5.6 lb/100 sq ft over 2 applications; roses 5.6 lb/100 sq ft over 2 applications; pink hydrangeas 4.2 lb/100 sq ft.

What to do next

If your test confirms pH near 5.66, spread about 56 lb of ground limestone per 1,000 sq ft of vegetable bed in 2 doses, ideally in fall.

How mixed the soil is

Of the 232,332 surveyed acres in Knox, KY, 49% are moderately acidic (5.5-6.5), 47% are strongly acidic (below 5.5), 4% are near neutral (6.5-7.3). Mapped soils run from pH 4.6 to 7.1, a spread of 2.5 units across 106 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 17.4% clay and 3.78% 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. None of the mapped components carry free carbonate.

Knox against the rest of Kentucky

pH 5.66 is 0.13 below the Kentucky median of 5.79. 43 of 120 Kentucky counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Hopkins (5.62), Jackson (5.63), Lee (5.65), Graves (5.66), Ohio (5.68), Pike (5.69), Hart (5.71), Lyon (5.71).

The range in Kentucky runs from Greenup at 5.09 to Carroll at 6.63; Knox sits 37% of the way up.