Soil pH in Rockcastle, KY: Lime or Sulfur?

Typical topsoil pH in Rockcastle, KY

Typical topsoil in Rockcastle, KY is pH 5.51, too acidic for vegetable garden. Expect roughly 7 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Rockcastle needs, by plant

• Already in range: potatoes, strawberries, azaleas and rhododendrons.
• Just outside, test first: blueberries (off by 0), blue hydrangeas (off by 0).
• Lime: lawn (cool-season grass) 7 lb/100 sq ft over 2 applications; vegetable garden 7 lb/100 sq ft over 2 applications; tomatoes 7 lb/100 sq ft over 2 applications; roses 7 lb/100 sq ft over 2 applications; pink hydrangeas 4.9 lb/100 sq ft.

What to do next

If your test confirms pH near 5.51, spread about 70 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 183,212 surveyed acres in Rockcastle, KY, 56% are strongly acidic (below 5.5), 32% are moderately acidic (5.5-6.5), 11% are near neutral (6.5-7.3). Mapped soils run from pH 4 to 7.3, a spread of 3.3 units across 153 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 18.3% clay and 2.61% 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.

Rockcastle against the rest of Kentucky

pH 5.51 is 0.28 below the Kentucky median of 5.79. 20 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: Johnson (5.49), Simpson (5.5), Bell (5.51), Butler (5.51), Breathitt (5.52), Grayson (5.52), Adair (5.53), Morgan (5.53).

The range in Kentucky runs from Greenup at 5.09 to Carroll at 6.63; Rockcastle sits 27% of the way up.