Soil pH in Clark, ID: Lime or Sulfur?

Typical topsoil pH in Clark, ID

Typical topsoil in Clark, ID is pH 7.19, just outside the 6-7 range for vegetable garden. Test first; it may need nothing.

What Clark 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 4.4 lb/100 sq ft over 3 applications; blue hydrangeas 4.4 lb/100 sq ft over 3 applications; pink hydrangeas 2.1 lb/100 sq ft over 2 applications.

What to do next

If your test lands near 7.19, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, roses.

How mixed the soil is

Of the 1,008,825 surveyed acres in Clark, ID, 44% are alkaline (above 7.3), 42% are near neutral (6.5-7.3), 14% are moderately acidic (5.5-6.5). Mapped soils run from pH 5 to 9, a spread of 4 units across 1,252 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 14.1% clay and 3.4% 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. 29% of mapped components carry free carbonate (lime already in the ground).

Clark against the rest of Idaho

pH 7.19 is 0.18 above the Idaho median of 7.01. 27 of 44 Idaho counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Gooding (7.04), Bonneville (7.1), Ada (7.18), Bear Lake (7.18), Elmore (7.26), Franklin (7.26), Twin Falls (7.27), Jerome (7.29).

The range in Idaho runs from Valley at 6.04 to Jefferson at 8.06; Clark sits 57% of the way up.