Soil pH in Washington, TN: Lime or Sulfur?

Typical topsoil pH in Washington, TN

Typical topsoil in Washington, TN is pH 5.4, too acidic for vegetable garden. Expect roughly 7.7 lb of lime per 100 sq ft, but only after a soil test confirms it.

What Washington needs, by plant

• Already in range: potatoes, blueberries, azaleas and rhododendrons, blue hydrangeas.
• Just outside, test first: strawberries (off by 0.1).
• Lime: lawn (cool-season grass) 7.7 lb/100 sq ft over 2 applications; vegetable garden 7.7 lb/100 sq ft over 2 applications; tomatoes 7.7 lb/100 sq ft over 2 applications; roses 7.7 lb/100 sq ft over 2 applications; pink hydrangeas 5.6 lb/100 sq ft over 2 applications.

What to do next

If your test confirms pH near 5.4, spread about 77 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 188,174 surveyed acres in Washington, TN, 47% are moderately acidic (5.5-6.5), 43% are strongly acidic (below 5.5), 9% are near neutral (6.5-7.3), 1% are alkaline (above 7.3). Mapped soils run from pH 4.5 to 7.5, a spread of 3 units across 209 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 24.5% clay and 1.76% 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.

Washington against the rest of Tennessee

pH 5.4 is 0.05 above the Tennessee median of 5.35. 54 of 95 Tennessee counties have more acidic topsoil. Nationally it is more acidic than the US county median of 6.05.

Closest in pH within the state: Pickett (5.37), Moore (5.38), Stewart (5.4), Sullivan (5.4), Benton (5.41), Cocke (5.41), Overton (5.41), Houston (5.44).

The range in Tennessee runs from Bledsoe at 4.78 to Lake at 6.59; Washington sits 34% of the way up.