Soil pH in Union, OR: Lime or Sulfur?

Typical topsoil pH in Union, OR

Typical topsoil in Union, OR is pH 6.89, already right for vegetable garden (6-7). Test before adding anything.

What Union needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, roses.
• Just outside, test first: tomatoes (off by 0.1).
• Sulfur: potatoes 3.2 lb/100 sq ft over 2 applications; strawberries 2.1 lb/100 sq ft over 2 applications; blueberries 4.4 lb/100 sq ft over 3 applications; azaleas and rhododendrons 3.7 lb/100 sq ft over 2 applications; blue hydrangeas 3.7 lb/100 sq ft over 2 applications; pink hydrangeas 1.4 lb/100 sq ft.

What to do next

If your test lands near 6.89, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, roses.

How mixed the soil is

Of the 577,653 surveyed acres in Union, OR, 82% are near neutral (6.5-7.3), 10% are alkaline (above 7.3), 9% are moderately acidic (5.5-6.5). Mapped soils run from pH 6 to 9, a spread of 3 units across 162 soil components. 82% 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 18.8% clay and 2.85% 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. 6% of mapped components carry free carbonate (lime already in the ground).

Union against the rest of Oregon

pH 6.89 is 0.59 above the Oregon median of 6.3. 27 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: Deschutes (6.75), Wasco (6.78), Crook (6.86), Jefferson (6.87), Sherman (6.94), Umatilla (6.96), Gilliam (6.99), Morrow (7.04).

The range in Oregon runs from Clatsop at 4.89 to Malheur at 7.9; Union sits 66% of the way up.