Soil pH in Klamath, OR: Lime or Sulfur?

Typical topsoil pH in Klamath, OR

Typical topsoil in Klamath, OR is pH 6.7, already right for vegetable garden (6-7). Test before adding anything.

What Klamath needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, tomatoes, roses.
• Just outside, test first: strawberries (off by 0.2), pink hydrangeas (off by 0.2).
• Sulfur: potatoes 2.8 lb/100 sq ft over 2 applications; blueberries 3.9 lb/100 sq ft over 2 applications; azaleas and rhododendrons 3.5 lb/100 sq ft over 2 applications; blue hydrangeas 3.5 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 6.7, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, strawberries, roses, pink hydrangeas.

How mixed the soil is

Of the 1,130,914 surveyed acres in Klamath, OR, 51% are near neutral (6.5-7.3), 35% are moderately acidic (5.5-6.5), 11% are alkaline (above 7.3), 2% are strongly acidic (below 5.5). Mapped soils run from pH 4.5 to 9.5, a spread of 5 units across 859 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 13.6% clay and 3.25% 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. 7% of mapped components carry free carbonate (lime already in the ground).

Klamath against the rest of Oregon

pH 6.7 is 0.4 above the Oregon median of 6.3. 21 of 36 Oregon counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Jackson (6.29), Hood River (6.31), Grant (6.43), Wheeler (6.58), Wallowa (6.72), Deschutes (6.75), Wasco (6.78), Crook (6.86).

The range in Oregon runs from Clatsop at 4.89 to Malheur at 7.9; Klamath sits 60% of the way up.