Soil pH in Jefferson, MT: Lime or Sulfur?

Typical topsoil pH in Jefferson, MT

Typical topsoil in Jefferson, MT is pH 6.95, already right for vegetable garden (6-7). Test before adding anything.

What Jefferson needs, by plant

• Already in range: lawn (cool-season grass), vegetable garden, roses.
• Just outside, test first: tomatoes (off by 0.2).
• Sulfur: potatoes 3.5 lb/100 sq ft over 2 applications; strawberries 2.3 lb/100 sq ft over 2 applications; blueberries 4.6 lb/100 sq ft over 3 applications; azaleas and rhododendrons 3.9 lb/100 sq ft over 2 applications; blue hydrangeas 3.9 lb/100 sq ft over 2 applications; pink hydrangeas 1.6 lb/100 sq ft.

What to do next

If your test lands near 6.95, you can skip lime and sulfur for lawn (cool-season grass), vegetable garden, tomatoes, roses.

How mixed the soil is

Of the 924,725 surveyed acres in Jefferson, MT, 58% are near neutral (6.5-7.3), 26% are alkaline (above 7.3), 15% are moderately acidic (5.5-6.5), 1% are strongly acidic (below 5.5). Mapped soils run from pH 4.2 to 9.1, a spread of 4.9 units across 5,204 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 18.6% clay and 2.69% 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. 28% of mapped components carry free carbonate (lime already in the ground).

Jefferson against the rest of Montana

pH 6.95 is 0.35 below the Montana median of 7.3. 17 of 56 Montana counties have more acidic topsoil. Nationally it is more alkaline than the US county median of 6.05.

Closest in pH within the state: Lake (6.69), Lewis and Clark (6.78), Beaverhead (6.79), Gallatin (6.85), Glacier (7.15), Hill (7.17), Phillips (7.17), Blaine (7.19).

The range in Montana runs from Flathead at 6.02 to Wheatland at 7.77; Jefferson sits 53% of the way up.