Soil pH in Walla Walla, WA: Lime or Sulfur?

Typical topsoil pH in Walla Walla, WA

Typical topsoil in Walla Walla, WA is pH 7.23, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Walla Walla needs, by plant

• Just outside, test first: lawn (cool-season grass) (off by 0.2), vegetable garden (off by 0.2), roses (off by 0.2).
• Sulfur: tomatoes 1.6 lb/100 sq ft; potatoes 3.9 lb/100 sq ft over 2 applications; strawberries 2.8 lb/100 sq ft over 2 applications; blueberries 5.1 lb/100 sq ft over 3 applications; azaleas and rhododendrons 4.6 lb/100 sq ft over 3 applications; blue hydrangeas 4.6 lb/100 sq ft over 3 applications; pink hydrangeas 2.3 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 7.23, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, roses.

How mixed the soil is

Of the 756,445 surveyed acres in Walla Walla, WA, 82% are near neutral (6.5-7.3), 17% are alkaline (above 7.3), 2% are moderately acidic (5.5-6.5). Mapped soils run from pH 5.6 to 9.3, a spread of 3.7 units across 286 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 10.3% clay and 1.81% 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. 19% of mapped components carry free carbonate (lime already in the ground).

Walla Walla against the rest of Washington

pH 7.23 is 0.82 above the Washington median of 6.41. 34 of 39 Washington counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Garfield (7.01), Asotin (7.04), Columbia (7.05), Lincoln (7.12), Franklin (7.32), Grant (7.37), Benton (7.44), Adams (7.45).

The range in Washington runs from Grays Harbor at 4.93 to Adams at 7.45; Walla Walla sits 91% of the way up.